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Review

Microbial Diversity and Adaptation under Salt-Affected Soils: A Review

1
Department of Soil Science and Agricultural Chemistry, Sri Karan Narendra Agriculture University, Jobner, Jaipur 303329, Rajasthan, India
2
Department of Microbiology, COBS&H, Chaudhary Charan Singh Haryana Agricultural University, Hisar 125004, Haryana, India
3
Department of Soil Science and Agriculture Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi 221005, Uttar Pradesh, India
4
Krishi Vigyan Kendra, Narkatiaganj, West Champaran 845455, Bihar, India
5
Department of Plant Pathology, Sri Karan Narendra Agriculture University, Jobner, Jaipur 303329, Rajasthan, India
*
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Sustainability 2022, 14(15), 9280; https://doi.org/10.3390/su14159280
Submission received: 16 March 2022 / Revised: 30 May 2022 / Accepted: 13 June 2022 / Published: 28 July 2022

Abstract

:
The salinization of soil is responsible for the reduction in the growth and development of plants. As the global population increases day by day, there is a decrease in the cultivation of farmland due to the salinization of soil, which threatens food security. Salt-affected soils occur all over the world, especially in arid and semi-arid regions. The total area of global salt-affected soil is 1 billion ha, and in India, an area of nearly 6.74 million ha−1 is salt-stressed, out of which 2.95 million ha−1 are saline soil (including coastal) and 3.78 million ha−1 are alkali soil. The rectification and management of salt-stressed soils require specific approaches for sustainable crop production. Remediating salt-affected soil by chemical, physical and biological methods with available resources is recommended for agricultural purposes. Bioremediation is an eco-friendly approach compared to chemical and physical methods. The role of microorganisms has been documented by many workers for the bioremediation of such problematic soils. Halophilic Bacteria, Arbuscular mycorrhizal fungi, Cyanobacteria, plant growth-promoting rhizobacteria and microbial inoculation have been found to be effective for plant growth promotion under salt-stress conditions. The microbial mediated approaches can be adopted for the mitigation of salt-affected soil and help increase crop productivity. A microbial product consisting of beneficial halophiles maintains and enhances the soil health and the yield of the crop in salt-affected soil. This review will focus on the remediation of salt-affected soil by using microorganisms and their mechanisms in the soil and interaction with the plants.

1. Introduction

The enhancement in crop productivity in proportion to the growing population for feeding has been a big challenge since the inception of agriculture. The Global Agricultural Productivity (GAP) (2018) index states that the fulfillment of the food demands of a population of 10 billion in 2050 is not possible at the current growth rate of food production [1]. Soil supports the sustainable survival and development of humans, along with air and water. Food security, water scarcity and environmental pollution are the most serious challenges for all people. Crop productivity is affected by many abiotic factors which include temperature, soil pH, pesticides and fertilizer application, heavy metal, drought and salinity [2] The global scarcity of water resources, environmental pollution and the increased salinization of soil and water are important issues at the beginning of the 21st century. Soil also faces different stresses such as heat stress, drought stress and salt stress. These soil stresses are responsible for a significant reduction in crop yield. Salt stress is one of the important stresses which plays important role in plant growth and development. Salt-affected soils occur all over the world, especially in arid and semi-arid regions. Globally, there are 1 billion ha of salt-affected soil, and in India, nearly 6.74 million ha−1 of the area is under salt-affected soil [3]. The increasing rate and expansion of areas under salinity stress have created an insecurity of food demands in many countries. The salinization of coastal belts in the delta regions of India, Myanmar and Bangladesh, which majorly contribute to world rice production, are facing danger to food security [4,5]. Irrigated salinity-stressed areas have caused USD 12 billion in global income loss annually [6]. Large areas in the Indian states of Rajasthan and Gujarat comprise saline-unproductive land in the form of saline lakes, salt depressions and saline swampy lands devoid of any vegetation or supporting very meager cover. The salt-stressed condition negatively affects important soil activities such as nitrification, respiration, microbial diversity, mineralization residues decomposition, etc. [7]. High fertilizer application also results in soil salinity and deteriorates crop productivity due to the imposition of an osmotic regulation, causing water extraction for plant growth and development [8,9]. Soils having excess salt on the soil surface and in the plant root zone in such an amount can retard the growth and development of plants. These soils are distributed relatively more extensively in the arid and semi-arid regions as compared to the humid regions [9]. The reclamation and management of such soils require specific approaches for long-term productivity. Physical and chemical processes have long been performed in the reclamation of saline soil. Physical process such as flushing, leaching and scraping, along with neutralizing agents such as gypsum and lime under alkali and acid soil, are practiced under chemical methods for the removal of soluble salts [10]. Salt-tolerant crops such as barley and canola are grown, however, due to a normal salt-tolerant ability; these crops could not reach the world level and were not able to perform under high salt concentrations [11]. Morton et al. (2019) has reported that despite vigorous efforts from researchers, only a few salt tolerance genes have been identified as having real applications in improving the productivity of saline soils [12]. A major focus in the coming decades would be on safe and eco-friendly methods by exploiting the beneficial micro-organisms in sustainable crop production [13]. The inoculation of some naturally occurring microbes in the soil ecosystem advances soil physico-chemical properties, soil microbial biodiversity, soil health, plant growth and crop productivity [14]. In the recent past, researchers have demonstrated that the use of halophilic plant growth-promoting rhizobacteria enhanced crop productivity and soil health [15]. So, this review will focus on the different types of microorganisms such as bacteria, fungi, mycorrhiza, cyanobacteria, etc., which are capable of the bioremediation of salt-affected soil.

2. Ecology of Saline Soil Microorganisms

The communities of microbial diversity play an important role in the nutrients cycling. Environmental stress in the soil affects the microorganism and becomes detrimental to the survival of the microbes, decreasing the activities of surviving cells because of the metabolic load imposed by the starting and activation of the stress-tolerant mechanisms [16,17,18,19]. Under a dry and hot environment where low humidity and soil salinity are the most stressful factors for soil microbial diversity, the activity and metabolism of the microorganisms decrease. The detrimental and negative effects are more in the rhizosphere of the plant because of the increase in the water absorption by the plants due to transpiration. Life under the stress of salinity has a requirement of high bioenergetics because the microflora need to maintain the osmotic equilibrium between the cytoplasm of the microbes and the surrounding environment. Microbes under salt stress conditions survive by excluding the sodium ions from the cell inside, so microorganisms require a high energy, which is sufficient for osmoregulation [20,21]. Cells are separated by the medium using a cell membrane, which is permeable to water. When the concentration of the salt increases in the surrounding medium of the cells and reaches a point where the solute concentration becomes high, the solute concentration inside the cells loses the water and leads to the risk of the drying out of the cell. Cells can tolerate the salt counterbalances that increase in the osmotic pressure. Microbes had to be able to survive at high salt or solute concentrations in the medium in order to maintain an equally high concentration of solute in the cell cytoplasm. The rising of the solute concentration in the cell cytoplasm can be achieved by the synthesis and accumulation of the small organic molecules, which are called compatible solutes because of their non-interference with cellular functions [22].
The accumulation of the potassium ions (K+) inside the cell cytoplasm is another short-term response strategy to escape in situations where the salt concentration has rapidly increased. The enzymatic process is affected by the high ions concentration; this is why most organisms synthesize the small organic molecules. Compatible solutes are accumulated in the cells, whereas the salt ions are toxic, as they interfere in the enzymatic activities, and sodium (Na+) and chlorine (Cl) must be excluded from the cells. The exclusion of the salt ions is possible through the cross-membrane protein pump. The binding of the K+ ions is responsible for the activation of more than 50 plant enzymes, so an increase in the concentration of salt or Na+ interferes with the binding of the K+ binding sites, which leads to the disruption of the metabolic processes [23].
The high concentration of sodium (Na+) ions results in the retardation of plant growth and produces necrosis symptoms in plants. A high concentration of Cl leads to a lack of chlorophyll by degrading it [24]. The high concentration of salt restricts the limit for the uptake of the water by the plant roots against the negative soil water potential. High salt concentrations also result in an imbalance in the uptake of the plant nutrients in the rhizosphere. The exposure of the microorganisms to the salt stress conditions changes the expression pattern of the RuBisCO enzyme, which helps in carbon dioxide (CO2) fixation and makes carbon compounds for energy synthesis and other reactions available. The different types of osmo-tolerant proteins are produced during harsh conditions, which helps in the water holding and helps plants to tolerate the exposure to salt stress levels.
The salt tolerant microbes are divided in to four groups by Kushner (1993), i.e., non-halophilic <0.2 M NaCl, slight halophilic 0.2–0.5 M NaCl, moderate halophilic 0.5–2.5 M NaCl and extreme halophiles >2.5 M NaCl. The halo-tolerant microorganisms can tolerate high salt concentration but grow best in media containing <0.2 M (1%) salt. This definition of “halo-tolerant” is widely accepted [25,26,27,28]. The saline soil consists of an abundance of halophilic microorganisms in the soil and most dominantly belong to the genera of Bacillus, Pseudomonas, Micrococcus and Alcaligenes [29]. Garabito et al. (1998) investigated the saline soil situated in different locations of Spain, where he isolated 71 microorganisms for halo-tolerant, gram-positive, endospore-forming and rod-shaped Bacillus genus [30]. The salinity affects the composition of the microbial diversity [19,31,32,33,34]; thus, the microbial genotypes are different in their tolerance to a low osmotic potential [34,35]. A low osmotic potential results in a decrease in the spore germination and growth of the hyphae and a variability in the morphology [36] and gene expression [37]. Fungi seem more sensitive towards the salinity environment and osmotic stress than other microorganisms [31,38,39]. Salinity in soil with different concentrations of NaCl resulted in a significant reduction in the total fungal count. Similarly, if the salinity level is >5%, then the number of bacteria and actinobacteria is drastically reduced [40].
The accumulation of the ions that are necessary for the metabolism of cells occurs in halo-tolerant microbes. The other mechanism of cell adaptation in salt stress conditions is the production of organic compounds that will neutralize the concentration gradient between the cell cytoplasm and soil solution. This mechanism of the adaptation results in the higher physiological activities of the microbial community and the consequences. The cell reduces the utilization of the substrate. A better understanding of the changes in the microbial biomass and its activity under salt stress conditions can be achieved by the consideration of water potential (osmotic potential, matrix potential), particularly low water content where the salt concentration increases in the saline soil. Electrical conductivity is an indicator of microbial stress under salt stress conditions. The microbial biomass is an important labile fraction of the soil organic matter (OM), which acts multifunctionally as an agent of the recycling and transformation of the soil nutrients and OM and also acts as a source of plant nutrients. Microbial secretion is also an important source of the enzyme which helps in the regulation of many mechanisms in soil. The nutrients available for the plants are regulated by rhizospheric microbial activity [19]. So many factors in the soil which affect the microbial community and its function influence the availability of the nutrients and the growth of plants.
The recycling of nitrogen (N) such as mineralization and the immobilization through microbial responses plays an important role in plant growth and development [41]. Nitrogen mineralization is the conversion of the organic nitrogen to an inorganic form of nitrogen, and immobilization is the reverse of mineralization. Both mineralization and nitrification were significantly retarded in the presence of NaCl; maximum inhibition occurred with 4000 mg NaCl kg−1 of soil. The inhibitory effect of NaCl on N mineralization was relatively higher in soils treated with NH4+. The results of this study suggest a greater sensitivity to NaCl by microorganisms that have assimilated NO3 [42]. Moreover, the presence of the NaCl retards the immobilization of the N.

3. Interaction of Plants and Microbes in Salt-Affected Soils

When the microorganisms are exposed to the high-osmotic environment, rapid fluxes of the cell water out of the cell take place, resulting in a reduction in the turgor and the dehydration of the cytoplasm. Different types of adaptation have been achieved against the outflow of the cell water. The osmotic equilibrium between the cytoplasm of the cell and the surrounding media is maintained by exposing the cytoplasm to high ionic strength. The first response of the cell to the osmotic upshift results in the efflux of cellular water, the uptake of K+ and the accumulation of the compatible solutes into the cell [43].
Salt stress (50–200 mM NaCl) in the legume crops restricts productivity because of the negative and adverse effects on the growth of the root nodule bacteria and host plant, the symbiotic development and the nitrogen fixation ability [44]. A decrease in nitrogen fixation by affecting nodule development and the symbiotic association in Vicia faba was observed under the salinity stress in cultural media [45]. However, after the full development of the root nodule under stress-free conditions, the nitrogen fixation continues even after the treatment of salt-stress conditions. The early prolific variety of Phaseolus vulgar is tolerated at low levels (48 mM NaCl) but not at higher levels (72 and 96 mM NaCl) of salt [46]. The strain GRA19 of Rhizobium leguminosarum biovar. Viciae was found to be tolerant to low levels of salt (50 mM) by comparing the growth under stress conditions to that in the absence of stress. Moreover, the growth of symbiotic N2 fixation (acetylene reduction activity) under saline conditions of the faba bean cultivar Alameda inoculated with GRA19 was reduced [47]. The same species of Rhizobium vary in terms of their salt tolerance, the tolerance of different species of Rhizobium to NaCl ranging from 100 to 650 mM [48,49].
Rhizobia show a marked variation in salt tolerance. A number of strains are inhibited by 100 Mm of NaCL salt [50,51,52], but growth at salt concentrations of more than 300 mmol has been reported for the strains of Sinorhizobium meliloti [53,54] and Rhizobium tropici [55]. Some alfalfa, acacia, prosopis and leucaena strains will tolerate 500 mmol−l NaCl [52,54].

4. Application Strategy of Halophilic Microbes

4.1. Halophilic Bacteria

These halophilic bacteria are capable of balancing the osmotic pressure in the environment. Moreover, the organisms that can survive in highly saline conditions and require salt for proper growth and development are called halophiles. They are very diverse, belonging to three domains of life, i.e., Bacteria, Eukarya and Archaea. They are inhabitants of the soda lakes, salt ponds and rock salt crystals as dormant cells [56,57]. There are two sorts of organisms: those that can tolerate salt and those that require salt for growth and development [58]. Halotolerance is a mechanism through which halophilic bacteria can maintain growth and development under salinity conditions.
The halophiles are classified as slight halophiles, moderate halophiles and extreme halophiles. Slight halophiles can grow optimally between a 0.2–0.0.5 M (1–3%) NaCl concentration. Moderate halophiles can grow with a 0.5–2.5 M (3–15%) NaCl concentration, and extreme halophiles are able to grow with a 2.5–5.2 M (15–30%) NaCl concentration. Halophiles are aerobic, anaerobic, heterotrophic, phototrophic and chemoautotrophic types found in different environments [59].
In agriculture, plants face various environmental abiotic stresses such as droughts, chilling salinity, nutrient deficiency, pathogens, heavy metals, etc. This stress problem leads to abnormalities in the growth and development of the plants. Due to low rainfall, high temperatures and poor-quality water in arid and semiarid areas, soil faces the salinity problem, which is considered as a major environmental stress [60]. Halophilic bacteria adapt to salinity by a different method, assisting the plant in surviving under salt stress circumstances. Plants have various biochemical and physiological strategies to live in salt-stressed soil, such as osmolyte production, antioxidant enzymes, hormones and ion exclusion. Aside from all of these plant defense systems, the bacterial community in the soil, such as halophilic bacteria, also plays a significant role in increasing salt tolerance in the soil.

4.2. Taxonomy of Halophilic Bacteria

Halophilic microorganisms are salt-loving organisms that belong to the order Halobacteriales and to the family Halobacteriaceae. The first halophilic microorganism was discovered in Utah’s Great Salt Lake and was called Halanaerobium praevalens, which was described and classified as a genus in the Bacteroidaceae family [61].
After that, new halophilic bacterial species and genera were identified based on 16S rRNA sequencing and the lipid profiling of the membrane. Different halophilic species have been listed in Table 1.

4.3. Adaptability Mechanisms of Halophilic Bacteria for Saline Environments

Water is the prime element which is the responsible for life. Living microorganisms have the adaptation ability to survive under adverse environments. Microorganisms that have not adapted to saline conditions will lose water, causing the cells to shrink and eventually die due to a lack of cellular structure and function. To avoid excessive water loss in such conditions and preserve cellular structure and function, halophilic bacteria have evolved two sorts of techniques to deal with high salt concentrations [89]. The first strategy is the salt-in strategy, while the second is the compatible solute strategy. Bacterial cells keep the internal and exterior environments osmotically equal by collecting a high concentration of KCl. This method is carried out by the cell by changes in various physiological metabolisms such as enzyme activity, cellular component production and the shape and function of some organelles. The high-salt-in method protects halophiles from a saline environment by accumulating inorganic ions intracellularly to keep the salt concentrations in their environment balanced. Bacterial cells keep the internal and exterior environments osmotically equal by collecting a high concentration of KCl. Halophiles consist of the Cl pumps and transfer Cl from the environment into the cytoplasm in this process. To enhance the uptake and release of Cl, arginines and lysines are placed at both ends of the channel [90].
Most of the halophilic microorganisms protect the cell from high salt concentrations by the accumulation of compatible solutes such as organic (proline, betaine, ectoine, trehalose) and inorganic solutes (K+, Mg2+, Na+) [91,92]. The osmolytes or compatible solutes are released in the cytoplasm by the bacterial cell itself or they are taken from the medium. Most of the bacteria lack the intracellular system for the active transport of water to nullify the external osmotic pressure. Therefore, the internal environment is maintained by the transport/synthesis of a group of compatible solutes without affecting the metabolic function of the cell [93,94]. According to the chemical nature, compatible solutes are classified as anionic solutes, zwitterionic solutes and non-charged solutes. Organic anions are used to balance the internal environment of the halophilic bacteria under high salty conditions. Halophilic bacteria such as Halomonas and Halobacterium synthesize ectoine and L-glutamte, respectively, to survive under the salinity-stressed conditions [95]. Some halotolerant bacteria including Bacillus, Pseudomonas, Aeromonas and Zymomonas use the polyols compounds such as sorbitol, arabitol, glycerol and mannitol for osmoadaptation under salt-stressed conditions [96]. Halophilic bacteria use neutral amino acid-derived zwitter solutes as osmolytes in salt-stressed conditions [97]. Betaine is a natural compound with a negative charge used as an osmolyte for the protection of cells in order to cope with high osmotic stress by maintaining an internal balance by the regulation of water inside the cell. Different halophilic bacteria such as Halomonas, Virgibacillus, Oceanobacillus and Polaribactercan synthesize betaine from the glycine with the primary amine methylated to form a quaternary amine. Some methanogens such as methanohalophilus and methanohalobium can accumulate and synthesize betaine by the methylation of glycine or choline oxidation [98,99,100]. Ectoine (cyclic tetrahydropyrimidine), which is either accumulated from the external environment or synthesized from the medium, is used as the osmolyte by the halophilic bacteria to protect against the salt-stressed conditions. This was detected from the Halorhodospora halochloris bacteria, which was isolated from the hypersaline Mono lake [101]. Ectoine osmolytes have been found in halotolerant and halophilic bacteria such as Halomonas, Oceanobacillus, Nesterenenkonia, Methylophaga and Methyllarcula [94,102,103]. Some polar and non-charged organic molecules have also been used as osmolytes to protect the cell from high salt-stressed conditions. Glycerol osmolyte has been detected in some bacteria and halotolerant yeast under salt-stressed conditions [93,104]. Some sugar molecules such as trehalose have been detected in the halotolerant and halophiles and have been used as compatible solutes to cope with dessication, heat, cold and a hypersaline environment. Some proteobacteria and marine cynobacteria are known to accumulate sucrose as an osmolyte in salt-stressed conditions. Some proteins such as proline, acetylated glutamine dipeptide and carboxamine also act as the osmolytes and protect the cell from high salt conditions. They are mostly found in halophilic purple sulfur bacteria and marine phototrophic bacteria [89] (Figure 1).

5. Halophilic Bacteria: Role of Halophilic Bacteria in Plant Growth Promotion under Salt Stress

During growth and development, each living organism or plant is subjected to the harsh conditions of the soil. To escape the stress circumstance, they will either fight or devise an alternative approach. Because plants are highly delicate and sessile, they cannot escape the bad conditions; thus, they fight back against them. With the aid of multiple mechanisms, halophilic bacteria boost their tolerance capacity, development and production and overcome the detrimental impacts of abiotic stress conditions with specific functional features.

5.1. The Role of Bacterial Phytohormones

Bacterial phytohormones are organic compounds that have a low concentration and impact the physiological and biological processes in plants. These tiny quantities of bacterial phytohormones influence the control of several processes involved in plant differentiation and development. Bacterial hormones, which are plant growth hormones secreted near the plant roots, can initiate a physiological response in the host plant. Plant growth-promoting bacteria (PGPB) generate phytohormones such as IAA, cytokinins, abscisic acid, gibberellins and other growth regulators that aid in plant growth and development. All of these phytohormones prolong root stimulation by dramatically increasing root length and surface area, which leads to increased nutrient absorption and hence enhances plant health in salt-challenged circumstances [105].

5.2. Aminocyclopropane-1-Carboxylate (ACC) Deaminase

In extremely low quantities, ethylene is an essential and volatile bacterial phytohormone that impacts plant growth regulation. Ethylene phytohormones influence the growth of plant vegetative parts, the rooting of cuttings and nodulation [106], as well as the transmission of signals for the response to salt stress surrounding the root zone [107]. The overproduction of ethylene hormones in response to abiotic stress situations can limit plant growth and development. Chemical inhibitors such as cobalt ions and aminoethoxyvinylglycine are commonly used to overcome these difficulties. However, these compounds are prohibitively costly and hazardous to the environment. Salt-tolerant bacteria can generate aminocyclopropane-1-carboxylate (ACC) deaminase, which converts ACC to α-ketobutyrate and ammonia, lowering the ethylene levels in salt-stressed plants [108].

5.3. Phosphate Solubilization

Phosphorous (P) is an important macronutrient that is required for the production of many biochemicals such as nucleotides, phospholipids, nucleic acid and phosphoprotein, as well as for plant growth and development. Under salt stress circumstances, the availability of phosphorus decreases, and signs of P shortage develop [109]. Organic and inorganic phosphorus are the two types of phosphorus present in soil. The mobility and availability of P to plants are quite low in comparison to other nutritional elements such as zinc, iron, copper, potassium and so on [110]. The majority of the phosphorous in the soil is in the insoluble form, making the mobility and availability of the P to the plant difficult or impossible. Halophilic strains aid in the conversion of insoluble P to soluble P and in the maintenance of soil P levels. A lot of research has been done on halotolerant strains that can solubilize and make phosphorus available. The phosphorus mobilization and absorption were demonstrated in the blackpaper, which resulted in increased root proliferation and plant growth [111]. Rhizobacterial strains can thrive in high salt conditions (60 g/LNaCl) and are effective P solubilizers in soil [112]. Under salt stress conditions, the pseudomonas strains had a substantial influence on the growth and development of Zea mays L. [113]. Under saline circumstances, PSB Herbaspirillum seropedicae and Burkholderia sp. inoculation increased crop weight by 1.5–21 percent [114].

5.4. Antioxidative Activity

The salt stress state induces the creation of reactive oxygen species, which destroys various biomolecules such as proteins and lipids and causes plant death [115]. Plants contain antioxidant processes that allow them to live in the presence of ROS [116]. There are many antioxidative enzymes (superoxide dismutase, peroxidase, and catalase) and non-enzymatic antioxidants (ascorbic acid, glutathione) that aid in the ROS scavenging processes [117]. Several halotolerant PGPR, such as S. proteamaculans and Rhizobium leguminosarum, are known to produce these enzymes (SOD, POX, CAT) and aid in the plant’s survival under salt stress conditions. It was recently discovered that salt-tolerant bacteria (P. simiae AU) enhance peroxidase and CAT gene expression in soybean plants following 100 mM NaCl of stress inoculation [118]. PGPR inoculation mitigates the harmful effects caused by the oxidative stress by enzymatic and non-enzymatic mechanisms under saline-stressed conditions. In the case of non-enzymatic mechanisms, they reduced the exposure to ROS by migrating to less solar radiation space. The pigment production and packaging of the DNA with proteins and chromatins provide alternate sites for the attack of reactive oxygen species. Some non-enzymatic antioxidant compounds also prevent reactive oxygen species. On the other side, the enzymatic method produces different enzymes such as superoxide dismutase, catalases, glutathione peroxidases, peroxiredoxins, etc. without generating more reactive species. Antioxidant enzymes transform the harmful products into less harmful molecules or locate them and degrade them. These methods also maintain the appropriate physiological levels of the reactive species such as ROS [119].

5.5. Siderophore Producers

Iron is an essential nutrient for plant growth and development because it functions as a cofactor in several metabolic processes and redox activities. Because the insoluble form of iron (ferric hydroxide) is present in the soil, it is not accessible to the plant and acts as a limiting nutrient for the plant’s growth and development. Abiotic stress causes iron to be unavailable, making microbe acquisition a significant issue [120]. Several bacteria with particular mechanisms are present, which help to solubilize the iron nutrient and make it accessible to the plants. Halotolerant bacteria assist the plant in surviving under salt stress conditions and increase iron availability through the synthesis of siderophores. Siderophores are tiny molecular weight compounds that chelate iron and transfer it into cells [121,122,123]. Halobacillus trueperi MXM-16 and the Chromocurvus halotolerans strain EG19 produced the siderophores that were hydroxamate in nature [124,125].

6. Arbuscular Mycorrhizal Fungi

Arbuscular mycorrhizal fungi are fungi that have a symbiotic relationship with terrestrial plant roots (AMF). Many scientists have studied the effect of mycorrhiza in plants’ adaptation to salt stress conditions. Mycorrhizal inoculation influences the ionic balance, nutrient solubilization and mobilization, photosynthesis efficiency, physiological and biochemical performance on plant development and helps to decrease salt tolerance (Figure 2) [126].
Arbuscular mycorrhizal fungi improved salt stress tolerance in the host plant by (a) increasing nutrient and water mobilization and uptake by the extensive hyphal network [127,128,129], (b) changing the plant morphology and physiology, allowing the plant to adapt to salt stress [130], (c) plant hormone production and (d) the interaction of mycor [131,132,133,134].
This AMF connection with plants improves water and nutrient intake, solubilizes nutrients and aids in nutrient cycling in soil, root architecture and the provision of vital nutrients to host plants under salt stress. Mycorrhizal fungi play a crucial role in ion regulation and membrane transport proteins, which govern the host plant’s ion homeostasis. As a result, it is clear that AMF association with plants considerably enhances the concentration of macro and micronutrients [135].
It has been discovered that AMF colonization considerably increases the chlorophyll content of numerous plants, including Solanum lycopersicum L. and lettuce [136,137]. Plants exposed to salt stress evolve several unique defensive mechanisms, such as increased osmolyte synthesis and antioxidant enzymes, to protect themselves from oxidative damage [138,139,140]. The AMF relationship dramatically increased antioxidant activities such as peroxidase, catalase, superoxide dismutase and others. During the early phases of the salt treatment, mycorrhization boosted the activity of numerous antioxidants, including superoxide dismutase (SOD), peroxidase (POD), ascorbate POD (ASA-POD) and catalase (Cat). Hajiboland et al. (2010) and Huang et al. (2010) investigated how AMF interaction with plants mitigates the oxidative stress caused by salt stress conditions by boosting antioxidant synthesis and scavenging reactive oxygen species (ROS) [136,141].
The proline content of salt-stressed AMF infected peanuts was similarly increased [142]. Sannazzaro et al. (2007) discovered proline and polyamine accumulation in two genotypes of Lotus glaber after inoculation with Glomus intraradices. Under salt-stressed circumstances, proline production was also seen in mycorrhiza-inoculated Cyamosis tetragonoloba and Glycine max [143,144].
Arbuscular mycorrhizal fungi, in addition to the factors mentioned above, play an important function in improving soil quality and health. Glomalin, a glycoprotein produced by AMF hyphae in the soil, aids in soil aggregation [145]. Although the precise process or gene responsible for glomalin synthesis is unknown, various studies have shown that glomalin and its related soil proteins generated by AMF might contribute to the construction of a “sticky” string bag of hyphae that would stabilize aggregation [146,147].
The favorable effect of mycorrhizal fungus on maize and cotton development under salt stress conditions was related to an increase in proline synthesis and phosphorus absorption [148]. Table 2 shows the responses of plants to AMF inoculation on host species subjected to salt stress treatments.

7. Cyanobacteria

Cyanobacteria are prokaryotic microorganisms that are capable of carbon (C) and nitrogen (N) fixation. Cyanobacteria or blue-green algae (BGA) provide 25–30% N ha−1 season−1 in rice fields [155].
Blue-green algae also improve soil health by providing extracellular carbohydrates, secondary metabolites and hormones. Cyanobacteria increase the soil porosity and water holding capacity of degraded soil due to the soil salinity and high chemical fertilizers application [156]. Eight BGA species such as Nostoc, Anabaena, Calothrix and Aulosira have been selected for field evaluation against pH, salinity and dessication in coastal areas of Orissa. Blue-green algae also help in the amelioration of sodic soil, as cyanobacteria are able to tolerate high sodium concentrations in wet seasons.
Halo-tolerant cyanobacteria (Nostoc calcicola) and the possible salt-tolerant mechanism are depicted in Figure 3 [157]. A study stated that the inoculation of cyanobacteria and gypsum changes the soil properties, which indicates the reclamation of the salt-affected soil. Cyanobacterial-treated soil showed significant decreases in pH, EC and Na+, and the organic carbon (OC) content increases significantly. A combination of Nostoc calcicola and gypsum seems effective for the treatment of the saline-alkaline soils. Some cyanobacteria release the cyanotoxin under stressed conditions and may have an impact on the seed germination and plant growth, but the phytotoxicity is concentration-dependent, and the field study of the phytotoxicity is inadequate [158].
Alkaline soils, which have high Na+ contents and pH values, enhance the growth of N-fixing cyanobacteria, with a significant decrease in pH. Different types of the organic metabolites released by cyanobacterial activities in the soils also help in maintaining the soil fertility year after year [159]. The addition of Nostoc calcicole to the saline/alkaline stress soil reduces the pH content, indicating the improved soil fertility. The dominant growth of Nostoc calcicola in saline/alkaline-stressed soils might be because of the salt tolerance capability, which suggests that Nostoc calcicole could be a good biological approach for soil reclamation. Singh (1961) recommended that BGA application can be effective for the reclamation of alkaline soils, as they are able to grow on these conditions, while other plants suffer to grow on them [160]. Pandey et al. (2005); Jaiswal et al. (2010) and Murtaza et al. (2011) have also suggested the role of cyanobacteria in the reclamation of saline-alkaline soils [161,162,163].

8. Plant Growth-Promoting Bacteria

Salt-affected soil is becoming more of a concern over time, and it might be the result of a natural or man-made process [164]. Different hemophilic plant growth-promoting bacteria (PGPB) are prevalent in soil and aid in the alleviation of salt stress by encouraging vegetal nutrition and development via the methods depicted in Figure 4.
The PGPB suppress several plant pathogenic microorganisms and promote plant growth by many mechanisms, such as the production of various plant hormones, mobilization and the decay of organic material, along with an increase in the bioavailability of various soil mineral nutrients such as iron (Fe) and phosphorous (P) [165]. The PGPB produce plant hormones such as auxins and cytokinins that encourage the proliferation of shoots and modify the root system by the overproduction of roots and root hairs, which results in the improvement of water and nutrients uptake by the plants. Several bacterial species such as Enterobacter sp. encourage plant development via ACC deaminase activity, HCN production, siderophore production, IAA production and the solubilization of P [166]. Two bacterial species such as Streptomyces rochei and Streptomyces sundarbansensis produce IAA and encourage plant growth [167]. Soil is the host of a massive number of bacteria (usually between 108 and 109 cells per gram of soil); however, out of this, only 1% are culturable [168]. Bacterial genera such as Streptomyces, Azospirillum, Clostridium, Alcaligenes, Bacillus, Rhizobium, Pseudomonas, Thiobacillus, Serratia and Klebsiella are found to be effective as PGPB under salt-affected conditions [169]. The different field trials of these species—inoculant or as a part of microbial consortia—have been found to be positive [170]. The PGPB have been found to be successful in maintaining osmotic potential, ion homeostasis and turgor potential, which helps in reducing the salt stress in plants [171]. The salt-tolerant microbial community helps in maintaining the health of salt-affected soil, sustains soil ecology and encourages the growth and development of plants [172]. Further research is required to determine the unknown mechanisms behind salt-tolerant microbial diversity [173].

8.1. Production of Phytohormone and ACC-Deaminase Activity

Plant growth-promoting bacteria are known to encourage the growth and development of plants by the synthesis of various plant hormones such as auxin, cytokinin, gibberellin and the minimization of ethylene by ACC deaminase. Ethylene is a well-known gaseous hormone that accumulates in plants under different abiotic stresses. The extent of ethylene buildup in plants varies by species and genus, as well as by organs and tissues. Ethylene is responsible for various development processes of plants such as the germination of seed, the development of root hairs, the ripening of fruits, the abscission of leaves and the senescence of plant parts by controlling various stress-related genes [174]. However, a higher accumulation of ethylene during stress conditions may become harmful for plant development [175]. The PGPB improve plant growth and help in salt tolerance by regulating the ethylene hormone level in plants through the ACC deaminase, which splits the ethylene precursor ACC to ammonia and α-ketobutyrate, which results in the improvement of plant growth and fights salt stress [176]. The PGPB through ACC deaminase activity alter the surface area of the root and the number of root tips. Hence, the PGPB promote nutrient accumulation and the survival of plants under stress situations. It has been found that the synthesis of the enzyme ACC deaminase and the decrease in ethylene production are the main causes of PGPB-mediated plant growth promotion under salt stress [177]. Auxins are another class of plant hormones that can be regulated by PGPB. The auxins group includes I3B (indole-3-butyric acid) and IAA (indole-3-acetic acid); the bacteria producing the auxins group are Actinobacteria, Nocardia, Frankia, Kitasatospora and Streptomyces.

8.2. Production of Extracellular Polymeric Substance

Soil microbes synthesize various biopolymers such as polysaccharides, polyamides and polyesters under natural conditions. Along with this, wide spectra of polysaccharides are produced, such as structural, intracellular, extracellular or exo-polysaccharides [178]. Plant growth-promoting bacteria produce an extracellular polymeric substance that has an important role in mitigating salt stress [112]; this extracellular polymeric substance has the capacity to combine with cations such as sodium, resulting in a decrease in the bioavailability of these cations for plant uptake. The extracellular polymeric substance increases bacterial survival under salt stress conditions by improving the water-holding ability of soil and controlling the flow of soil organic carbon. The extracellular polymeric substance also aids in the formation of plant–microbe interactions [179] by giving a microenvironment where microorganisms can live under salt stress conditions. Root exudates support microbes in contacting the roots of plants and colonizing them. The amount and composition of extracellular polymeric substances change dramatically during salt and drought stress conditions. The extracellular polymeric substance is produced by microorganisms such as slime material which bind with soil particles by a Van der Waal attraction, hydrogen bond, cation linkage and anion adsorption phenomenon [176].

8.3. Production of Plant Osmolytes and Antioxidant Activity

Plant growth-promoting bacteria synthesize organic osmolytes such as sugars, glucosyl glycerol, alcohols, betaines, amino acids, tetra-hydropyrimidine, etc. [101]. Organic solutes found in the cytoplasm of bacteria can or cannot be synthesized by bacteria; sometimes the organic osmolytes are taken up from the outer environment [101]. The presence of this osmolyte helps to combat salt stress. The osmolytes produced in the cytoplasm help in maintaining the osmotic balance of plant cells. Some common plant osmolytes include di- and oligosaccharides, betaine, proline, alcohols, glutamate and glycine [180]. Osmo protectants such as sugars and primary disaccharides such as sucrose and oligosaccharides such as raffinose and fructans are the basic drivers behind plant stress management. Sucrose production is connected with the survival of Craterostigma plantagineum during plant tissue dehydration [181]. During salinity stress, a higher fraction of the cellular energy deviated towards the formation of osmolytes is capable of defending the cells from osmotic fluctuations [182]. Osmolyte buildups preserve turgor pressure and balance the different macromolecular structures towards the physiological drought caused by salt stress [183].

8.4. Siderophore Production

The bacterial strains producing siderophores have a higher affinity for iron than phytosiderophores; therefore, they can remove Fe from the phytosiderophore complex. Researchers reported that the activities of microorganisms have a significant effect on the accumulation of iron in roots and its transport to other plant parts [184]. As reported by Rungin et al. (2012), the siderophore-producing endophytes increase plant root and shoot biomass because of the enhanced supply of iron. Siderophore-producing PGPB have been found to be successful in improving salt tolerance in the plant [185,186].

8.5. Induced Systemic Resistance

Induced systemic resistance (ISR) is the improved protection capability created by a plant against different types of plant pathogens succeeding in root colonization by microbes [187]. In addition to ethylene and jasmonate, other microbial substances such as pyoverdine, flagellar proteins, β-glucans, chitin, salicylic acid and cyclic lipopeptide surfactants have been found to operate as signals to stimulate systemic tolerance [188]. Plants create tolerance in response to pathogen and insect attacks and the colonization by microorganisms; however, this mediated condition is revealed by the stimulation of “dormant” immune responses reflected in the reaction to the external interactions of insects, pathogens and other invaders [189].

8.6. Essential Nutrient Uptake

Salt stress to plants reduces their nutrients uptake and accumulation capabilities such as N, P and K, along with their water uptake due to high osmotic potential and ion toxicity. Therefore, plants need more nutrients to survive in stress situations [190]. Crop yield is adversely affected in salt-affected soils because of the hindering nutrient uptake and translocation [191]. Plant-associated PGPB are well known for promoting water and nutrient absorption by plants [192]. The PGPB inoculation to plants increases nitrogen accumulation by a symbiotic and non-symbiotic relationship with the roots [193]. Phosphorus is found in organic and inorganic fixed forms in soils, and its major part is unavailable to plants. PGPB can convert these unavailable phosphorus forms into available forms by the mechanism of acidification and chelation processes [194]. Potassium is also an essential nutrient to plant growth; most of the K is found in fixed forms in the soil that are not available for plant uptake. Moreover, under salt stress conditions, the availability of potassium to plants decreases; under this situation, K-solubilizing bacteria (KSB) were found to be efficient in fulfilling the potash requirement of crops [195]. The K-solubilizing bacteria (KSB) group can convert mineral potash into available forms for plant uptake [196]. PGPB (Plant growth-promoting bacteria) enhance the availability of other essential elements such as copper, iron, manganese, zinc, etc. for the plants by the mechanism of chelation and acidification in soil [194]. Organic phosphate is resistant to mineralization. The microbial biomass is very important in the phosphorous cycle; microbes make it available for the plants [197].

9. Microbial Inoculation Influencing Soil Properties

Soil microbial diversity plays important role in improving soil health by controlling the supply of nutrients and the decomposition of OM, thus enhancing nutrient availability to plants. The production of different enzymes, hormones and macro-aggregates helps to sustain soil health. The salinity stress of soil drastically reduces the microbial diversity in the soil. Soil with good health conditions consist of around 600 million microorganisms in one gram of soil, with 15,000–20,000 distinct species, but the same amount is reduced to 1 million in salt-affected soil [198]. Salinity reduces microbial activity, microbial modification and OM degradation [199]. Furthermore, the different microbial groups in soils play a key role in the soil regulatory process for the nutrients cycling in salt-affected soil [200].
Fungal and bacterial abundance also play an important role in controlling soil respiration, which is a direct effect of microbial abundance on soil. However, changes in microbial abundance are also largely driven by soil properties [201]. The specialized soil functioning (e.g., denitrification) relies on specific groups of micro-organisms and is highly dependent on bacterial community composition [202]. The cementing properties of exopolysaccharides (EPS) strengthen the aggregate formation of the bacteria with the soil particles and bind Na ions, thereby reducing their toxicity in the soil. Therefore, a higher population of EPS-producing bacteria in the root zone will reduce the concentration of Na+ available for uptake, thereby alleviating the salt stress effect on the plants [203].

10. Future Challenges for Salt Stress Mitigation through Halophilic Microbes

The identified halophilic plant growth-promoting microbes needs to be applied in agriculture to enhance crop yields under salt stress conditions. The development of biological products based on beneficial halophiles can extend the range of options for maintaining the healthy yield of crops in salt-affected soils. In recent years, a new approach has been developed to alleviate salt stress in plants by inoculating crop seeds and seedlings with salt-tolerant plant growth-promoting microbes. Thus, there is a great opportunity for halophilic PGPR’s successful application in agriculture. The microbial formulation and application technology are crucial for the development of commercial salt-tolerant bio-formulation effective under salt stress conditions. Bio-formulations offer an environmentally sustainable approach to increasing crop production and health. Apart from microbial reclamation, improving the fertility of salt-stressed soils is another aim to be focused on. It has been observed that inoculation with mixed strains is more consistent than single-strain inoculations. Studies on the detailed mechanism of mycorrhizal fungi-associated plant growth under salt stress are lacking, and this needs to be explored. The promising approach toward tackling the problem of soil salinity by utilizing beneficial microorganisms including halophilic PGPR will make the greatest contribution to the agricultural economy, as they provide a cheap and eco-friendly approach to mitigate salt stress.
One of the recent focuses of research involves the application of PGPR to combat salt stress. The development of biological products based on beneficial microorganisms can extend the range of options for maintaining the healthy yield of crops in saline habitats. In recent years, a new approach has been developed to alleviate salt stress in plants by treating crop seeds and seedlings with PGPR. The great opportunity for salt tolerance research is its ability to be combined with halophilic PGPR.
The bottom line of every inoculation technology is its successful application under agricultural and industrial conditions. The microbial formulation and application technology are crucial for the development of commercial salt-tolerant bioformulation that is effective under salt-stress conditions. Bioformulations offer an environmentally sustainable approach to increase crop production and health, contributing substantially to making the twenty-first century the age of biotechnology. Apart from bioformulation, reclaiming and improving the fertility of stressed sites is another aim to be focused on. The promising approach toward tackling the problem of soil salinity by utilizing beneficial microorganisms including PGPR will make the greatest contribution to the agricultural economy—if inexpensive and easy-to-use stress tolerant strain formulations could be developed.

11. Conclusions

Despite the overall growth of salt-affected soils and the challenges associated with their reclamation and management, this review assessed current information on salt-affected soils and their bioremediation using various microbial techniques. The microbial consortium is playing an essential role in the long-term growth of agriculture. Similarly, halophilic bacteria can aid in the reduction of salt-stressed soil. So, plant growth-promoting rhizobacteria that thrive in salt-stressed soil must be employed in salt-affected soil for long-term growth and development. The development and application of halophilic plant growth-promoting microorganisms may aid in the long-term production of crops under salt-affected soil conditions. The creation of favorable halophile microbial formulations can broaden the number of choices for sustaining the crop output in salt-affected soils.

Author Contributions

Conceptualization the article structure and content: C.K., A.K., J.P. and A.P.; Defined the literature search criteria: A.P., C.K., J.P., P.D. and A.K.; Data handling, tables, and figures preparation: C.K., J.P., A.K., A.P., S.S.S. and P.D.; Writing–original draft: A.P., C.K., S.S.S. and P.D.; Writing–review and editing: A.P., C.K., A.K., J.P., S.S.S., P.D., G.K.Y., S.K.D., R.V. and G.L.K. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data and materials will be made available on from the corresponding author(s) upon reasonable request.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. GAP Report. Global Agricultural Productivity Report (GAP Report); Global Harvest Initiative: Washington, DC, USA, 2018. [Google Scholar]
  2. Ahmad, P. Oxidative Damage to Plants: Antioxidant Networks and Signaling; Academic Press: Cambridge, MA, USA, 2014. [Google Scholar]
  3. Kumar, P.; Sharma, P.K. Soil salinity and food security in India. Front. Sustain. Food Syst. 2020, 4, 533781. [Google Scholar] [CrossRef]
  4. Abedin, M.A.; Habiba, U.; Shaw, R. Salinity Scenario in Mekong, Ganges, and Indus River Deltas Water Insecurity: A Social Dilemma; Emerald Group Publishing Limited: Bingley, UK, 2014; pp. 115–138. [Google Scholar]
  5. Szabo, S.; Hossain, M.S.; Adger, W.N.; Matthews, Z.; Ahmed, S.; Lázár, A.N. Soil salinity, household wealth and food insecurity in tropical deltas: Evidence from south-west coast of Bangladesh. Sustain. Sci. 2016, 11, 411–421. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  6. Ghassemi, F.; Jakeman, A.J.; Nix, H.A. Salinisation of Land and Water Resources: Human Causes, Extent, Management and Case Studies; CAB International: Wallingford, UK, 1995. [Google Scholar]
  7. Schirawski, J.; Perlin, M.H. Plant-microbe interaction 2017-the good, the bad and the diverse. Int. J. Mol. Sci. 2018, 19, 1374. [Google Scholar] [CrossRef] [Green Version]
  8. Rütting, T.; Aronsson, H.; Elin, S. Efficient use of nitrogen in agriculture. Nutr. Cycl. Agroecosys. 2018, 110, 1–5. [Google Scholar] [CrossRef] [Green Version]
  9. Richards, L.A. Diagnosis and Improvement of Saline and Alkali Soils, U.S.D.A. Agriculture Handbook No. 60; US Department of Agriculture: Washington, DC, USA, 1954; p. 158.
  10. Ayyam, V.; Palanivel, S.; Chandrakasan, S. Approaches in land degradation management for productivity enhancement. In Coastal Ecosystems of the Tropics—Adaptive Management; Springer: Singapore, 2019. [Google Scholar]
  11. Fita, A.; Rodriíguez-Burruezo, A.; Boscaiu, M.; Prohens, J.; Vicente, O. Breeding and domesticating crops adapted to drought and salinity: A new paradigm for increasing food production. Front. Plant Sci. 2015, 6, 978. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  12. Morton, M.J.; Awlia, M.; Al-Tamimi, N.; Saade, S.; Pailles, Y.; Negrão, S. Salt stress under the scalpel-dissecting the genetics of salt tolerance. Plant J. 2019, 97, 148–163. [Google Scholar] [CrossRef] [Green Version]
  13. Nina, K.; Thomas, W.K.; Prem, S.B. Beneficial Organisms for Nutrient Uptake. VFRC Report 2014/1, Virtual Fertilizer Research Center; Wageningen Academic Publishers: Washington, DC, USA, 2014; p. 63. [Google Scholar]
  14. Sahoo, R.K.; Ansari, M.W.; Dangar, T.K.; Mohanty, S.; Tuteja, N. Phenotypic and molecular characterization of efficient nitrogen fixing Azotobacter strains of the rice fields. Protoplasma 2013, 251, 511–523. [Google Scholar] [CrossRef]
  15. Grover, M.; Ali, S.Z.; Sandhya, V.; Rasul, A.; Venkateswarlu, B. Role of microorganisms in adaptation of agriculture crops to abiotic stresses. World J. Microbiol. Biotechnol. 2011, 27, 1231–1240. [Google Scholar] [CrossRef]
  16. Schimel, J.P.; Balser, T.C.; Wallenstein, M. Microbial stress response physiology and its implications for ecosystem function. Ecology 2007, 88, 1386–1394. [Google Scholar] [CrossRef]
  17. Yuan, B.C.; Li, Z.Z.; Liu, H.; Gao, M.; Zhang, Y.Y. Microbial biomass and activity in salt affected soils under arid conditions. Appl. Soil Ecol. 2007, 35, 319–328. [Google Scholar] [CrossRef]
  18. Ibekwe, A.M.; Poss, J.A.; Grattan, S.R.; Grieve, C.M.; Suarez, D. Bacterial diversity in cucumber (Cucumis sativus) rhizosphere in response to salinity, soil pH, and boron. Soil Biol. Biochem. 2010, 42, 567–575. [Google Scholar] [CrossRef]
  19. Chowdhury, N.; Marschner, P.; Burns, R.G. Soil microbial activity and community composition: Impact of changes in matric and osmotic potential. Soil Biol. Biochem. 2011, 43, 1229–1236. [Google Scholar] [CrossRef]
  20. Oren, A. Molecular ecology of extremely halophilic archaea and bacteria. FEMS Microbiol. Ecol. 2002, 39, 1–7. [Google Scholar] [CrossRef] [PubMed]
  21. Jiang, H.; Dong, H.; Yu, B.; Liu, X.; Li, Y.; Ji, S.; Zhang, C.L. Microbial response to salinity change in Lake Chaka, a hypersaline lake on Tibetan plateau. Environ. Microbiol. 2007, 9, 2603–2621. [Google Scholar] [CrossRef] [PubMed]
  22. Wood, J.M. Bacterial Osmoregulation: A Paradigm for the Study of Cellular Homeostasis. Annu. Rev. Microbiol. 2011, 65, 215–238. [Google Scholar] [CrossRef] [Green Version]
  23. Tester, M.; Davenport, R. Na+ tolerance and Na+ transport in higher plants. Ann. Bot. 2003, 91, 503–527. [Google Scholar] [CrossRef]
  24. Tavakkoli, E.; Rengasamy, P.; McDonald, G.K. High concentrations of Na+ and Clions in soil solution have simultaneous detrimental effects on growth of faba bean under salinity stress. J. Exp. Bot. 2010, 61, 4449–4459. [Google Scholar] [CrossRef]
  25. Kushner, D.J. Growth and nutrition of halophilic bacteria. In The Biology of Halophilic Bacteria; Vreeland, R.H., Hochstein, L.I., Eds.; CRC Press: Boca Raton, FL, USA, 1993; pp. 87–89. [Google Scholar]
  26. Arahal, D.R.; Ventosa, A. Moderately halophilic and halotolerant species of Bacillus and related genera. In Applications and Systematic of Bacillus and Relatives; Berkeley, R., Heyndrickx, M., Logan, N., De Vos, P., Eds.; Wiley: Hoboken, NJ, USA, 2002; pp. 83–99. [Google Scholar]
  27. Ventosa, A.; Nieto, J.J.; Oren, A. Biology of moderately halophilic aerobic bacteria. Microbiol. Mol. Biol. Rev. 1998, 62, 504–544. [Google Scholar] [CrossRef] [Green Version]
  28. Yoon, J.H.; Kim, I.G.; Kang, K.H.; Oh, T.K.; Park, Y.H. Bacillus marisflavi sp. nov. and Bacillus aquimaris sp. nov. isolated from sea water of a tidal flat of the yellow sea in Korea. Int. J. Syst. Evol. Microbiol. 2003, 53, 1297–1303. [Google Scholar] [CrossRef] [Green Version]
  29. Rodriguez-Valera, F. Characteristics and microbial ecology of hypersaline environments. In Halophilic Bacteria; Rodriguez-Valera, F., Ed.; CRC Press: Boca Raton, FL, USA, 1988; Volume 1, pp. 3–30. [Google Scholar]
  30. Garabito, M.J.; Marquez, M.C.; Ventosa, A. Halotolerant Bacillus diversity in hypersaline environments. Can. J. Microbiol. 1998, 44, 95–102. [Google Scholar] [CrossRef]
  31. Pankhurst, C.E.; Yu, S.; Hawke, B.G.; Harch, B.D. Capacity of fatty acid profiles and substrate utilization patters to describe differences in soil microbial communities associated with increased salinity or alkalinity at three locations in South Australia. Biol. Fertil. Soils 2001, 33, 204–217. [Google Scholar] [CrossRef]
  32. Gros, R.; Poly, F.; Jocteur-Monrozier, L.; Faivre, P. Plant and soil microbial community responses to solid waste leachates diffusion on grassland. Plant Soil 2003, 255, 445–455. [Google Scholar] [CrossRef]
  33. Gennari, M.; Abbate, C.; La Porta, V.; Baglieri, A.; Cignetti, A. Microbial response to Na2SO4 additions in a volcanic soil. Arid Land Res. Manag. 2007, 21, 211–227. [Google Scholar] [CrossRef]
  34. Llamas, D.P.; Gonzales, M.D.; Gonzales, C.I.; Lopez, G.R.; Marquina, J.C. Effects of water potential on spore germination and viability of Fusarium species. J. Ind. Microbiol. Biotechnol. 2008, 35, 1411–1418. [Google Scholar] [CrossRef]
  35. Mandeel, Q.A. Biodiversity of the genus Fusarium in saline soil habitats. J. Basic Microbiol. 2006, 46, 480–494. [Google Scholar] [CrossRef]
  36. Juniper, S.; Abbott, L.K. Soil salinity delays germination and limits growth of hyphae from propagules of arbuscular mycorrhizal fungi. Mycorrhiza 2006, 16, 371–379. [Google Scholar] [CrossRef]
  37. Liang, Y.; Chen, H.; Tang, M.J.; Shen, S.H. Proteome analysis of an ectomycorrhizal fungus Boletus edulis under salt shock. Mycol. Res. 2007, 111, 939–946. [Google Scholar] [CrossRef]
  38. Sardinha, M.; Muller, T.; Schmeisky, H.; Joergensen, R.G. Microbial performance in soils along a salinity gradient under acidic conditions. Appl. Soil Ecol. 2003, 23, 237–244. [Google Scholar] [CrossRef]
  39. Wichern, J.; Wichern, F.; Joergensen, R.G. Impact of salinity on soil microbial communities and the decomposition of maize in acidic soils. Geoderma 2006, 137, 100–108. [Google Scholar] [CrossRef]
  40. Omar, S.A.; Abdel-Sater, M.A.; Khallil, A.M.; Abdalla, M.H. Growth and enzyme activities of fungi and bacteria in soil salinized with sodium chloride. Folia Microbiol. 1994, 39, 23–28. [Google Scholar] [CrossRef]
  41. Herrmann, A.; Witter, E.; Katterer, T. A method to assess whether ‘preferential use’ occurs after 15N ammonium addition: Implication for the 15N isotope dilution technique. Soil Biol. Biochem. 2005, 37, 183–186. [Google Scholar] [CrossRef]
  42. Azam, F.; Ifzal, M. Microbial populations immobilizing NH4+-N and NO3-N differ in their sensitivity to sodium chloride salinity in soil. Soil Biol. Biochem. 2006, 38, 2491–2494. [Google Scholar] [CrossRef]
  43. Whatmore, A.M.; Chudek, J.A.; Reed, R.H. The effects of osmotic cupshock on the intracellular solute pools of Bacillus subtilis. J. Gen. Microbiol. 1990, 136, 2527–2535. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  44. Bekki, A.; Trinchant, J.C.; Rigaud, J. Nitrogen fixation (C2H4 reduction) by Medicago nodules and bacteroids under sodium chloride stress. Physiol. Plant. 1987, 71, 61–67. [Google Scholar] [CrossRef]
  45. Yousef, A.N.; Sprent, J.I. Effect of NaCl on growth, nitrogen incorporation and chemical composition of inoculated and NH4NO3 fertilized Vicia faba L. plants. J. Exp. Bot. 1983, 143, 941–950. [Google Scholar] [CrossRef]
  46. Wignarajah, K. Growth response of Phaseolus vulgaris to varying salinity regimes. Environ. Exp. Bot. 1990, 2, 141–147. [Google Scholar] [CrossRef]
  47. Cordovilla, M.P.; Ocana, A.; Ligero, F.; Liuch, C. Salinity effects on grouth analysis and nutrient composition in four grain legumes-Rhyzobium symbiosis. J. Plant Nutr. 1995, 8, 1595–1609. [Google Scholar] [CrossRef]
  48. Tu, J.C. Effect of salinity on Rhizobium-root hair interaction, nodulation and growth of soybean. Can. J. Plant Sci. 1981, 61, 231–239. [Google Scholar] [CrossRef]
  49. Bernard, T.; Pocard, J.; Perroud, B.; Le Redulier, P. Variation in the response of salt stressed Rhizobium strains to betaine. Arch. Microbiol. 1986, 143, 359–364. [Google Scholar] [CrossRef]
  50. Singleton, P.W.; Swaify, S.A.; Bohlool, B.B. Effect of salinity on Rhizobium growth and survival. Appl. Environ. Microbiol. 1982, 44, 884–890. [Google Scholar] [CrossRef] [Green Version]
  51. Yelton, M.M.; Yang, S.S.; Edie, S.A.; Lim, S.T. Characterzation of an effective salt tolerant fast-growing strain of Rhizobium japonicum. J. Gen. Microbiol. 1983, 129, 1537–1547. [Google Scholar]
  52. Zhang, X.; Harper, R.; Karsisto, M.; Lindström, K. Diversity of Rhizobium bacteria isolated from the root nodules of leguminous trees. Int. J. Syst. Bacteriol. 1991, 41, 104–113. [Google Scholar] [CrossRef]
  53. Graham, P.H.; Parker, C.A. Diagnostic features in the characterization of the root nodule bacteria of legumes. Plant Soil 1964, 20, 383–396. [Google Scholar] [CrossRef]
  54. Sauvage, D.; Hamelin, J.; Larher, F. Glycine betaine and other structurally related compounds improve the salt tolerance of Rhizobium meliloti. Plant Sci. Lett. 1983, 31, 291–302. [Google Scholar] [CrossRef]
  55. Graham, P.H. Stress tolerance in Rhizobium and Brady Rhizobium and nodulation under adverse soil conditions. Can. J. Microbiol. 1992, 38, 475–484. [Google Scholar] [CrossRef]
  56. Woese, C. The Archaea: Their history and significance. In The Biochemistry of Archaea (Archaebacteria); Kates, M., Kushner, D., Matheson, A., Eds.; Elsevier: Amsterdam, The Netherlands, 1993; pp. 7–29. [Google Scholar]
  57. Choudhary, D.K.; Varma, A.; Tuteja, N. Plant-Microbe Interaction: An Approach to Sustainable Agriculture; Springer: Singapore, 2016. [Google Scholar]
  58. Larsen, H. Halophilic and halotolerant microorganisms—An overview and historical perspective. FEMS Microbiol. Rev. 1986, 39, 3–7. [Google Scholar] [CrossRef]
  59. Oren, A. Microbial life at high salt concentrations: Phylogenetic and metabolic diversity. Saline Syst. 2008, 4, 2. [Google Scholar] [CrossRef] [Green Version]
  60. Shakirova, F.M.; Sakhabutdinova, A.R.; Bezrukova, M.V.; Fatkhutdinova, R.A.; Fatkhutdinova, D.R. Changes in the hormonal status of wheat seedlings induced by salicylic acid and salinity. Plant Sci. 2003, 164, 317–322. [Google Scholar] [CrossRef]
  61. Zeikus, J.G.; Hegge, P.W.; Thompson, T.E.; Phelps, T.J.; Langworthy, T.A. Isolation and descriptionof Haloanaerobium praevalens gen. nov. and sp. nov. J. Biotechnol. 1983, 152, 114–124. [Google Scholar]
  62. Ahn, J.; Park, J.W.; Mc Connell, J.A.; Ahn, Y.B.; Häggblom, M.M. Kangiella spongicola sp. nov. a halophilic marine bacterium isolated from the sponge Chondrilla nucula. Int. J. Syst. Evol. Microbiol. 2011, 61, 961–964. [Google Scholar] [CrossRef]
  63. Gales, G.; Chehider, N.; Joulian, C.; Battaglia-Brunet, F.; Cayol, J.L.; Postec, A.; Borgomano, J.; Neria-Gonzalez, I.; Lomans, B.; Ollivier, B. Characterization of Halanaerocella petrolearia gen. nov. sp. nov. a new anaerobic moderately halophilic fermentative bacterium isolated from a deep subsurface hypersaline oil reservoir. Extremophiles 2011, 15, 565–571. [Google Scholar] [CrossRef] [PubMed]
  64. Jiang, F.; Cao, S.-J.; Li, Z.H.; Fan, H.; Li, H.F.; Liu, W.J.; Yuan, H.L. Salisediminibacterium halotolerans gen. nov. sp. nov. a halophilic bacterium isolated from Xiarinaoer soda lake sediment in Inner Mongolia, China. Int. J. Syst. Evol. Microbiol. 2011, 62, 2127–2132. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  65. Pugin, B.; Blamey, J.M.; Baxter, B.K.; Wiegel, J. Amphibacillus cookii sp. nov. a facultatively aerobic, spore-forming, moderately halophilic, alkalithermotolerant bacterium. Int. J. Syst. Evol. Microbiol. 2012, 62, 2090–2096. [Google Scholar] [CrossRef] [PubMed]
  66. Blum, J.S.; Kulp, T.R.; Han, S.; Lanoil, B.; Saltikov, C.W.; Stolz, J.F.; Miller, L.G.; Oremland, R.S. Desulfohalophilus alkaliarsenatis gen. nov. sp. nov. an extremely halophilic sulfate-and arsenate-respiring bacterium from Searles Lake California. Extremophiles 2012, 16, 727–742. [Google Scholar] [CrossRef] [Green Version]
  67. Mezghani, M.; Alazard, D.; Karray, F.; Cayol, J.L.; Joseph, M.; Postec, A.; Fardeau, M.L.; Tholozan, J.L.; Sayadi, S. Halanaerobacter jeridensis sp. nov. isolated from a hypersaline lake. Int. J. Syst. Evol. Microbiol. 2012, 62, 1970–1973. [Google Scholar] [CrossRef]
  68. Echigo, A.; Minegishi, H.; Shimane, Y.; Kamekura, M.; Usami, R. Natribacillus halophilus gen. nov. sp. nov. a moderately halophilic and alkalitolerant bacterium isolated from soil. Int. J. Syst. Evol. Microbiol. 2012, 62, 289–294. [Google Scholar] [CrossRef]
  69. Wang, Y.X.; Liu, J.H.; Xiao, W.; Zhang, X.X.; Li, Y.Q.; Lai, Y.H.; Ji, K.Y.; Wen, M.L.; Cui, X.L. Fodinibius salinus gen. nov. sp. nov. a moderately halophilic bacterium isolated from a salt mine. Int. J. Syst. Evol. Microbiol. 2012, 62, 390–396. [Google Scholar] [CrossRef]
  70. Ishikawa, M.; Yamasato, K.; Kodama, K.; Yasuda, H.; Matsuyama, M.; Okamoto-Kainuma, A.; Koizumi, Y. Alkalibacterium gilvum sp. nov. slightly halophilic and alkaliphilic lactic acid bacterium isolated from soft and semi-hard cheeses. Int. J. Syst. Evol. Microbiol. 2013, 63, 1471–1478. [Google Scholar] [CrossRef] [Green Version]
  71. Echigo, A.; Minegishi, H.; Shimane, Y.; Kamekura, M.; Itoh, T.; Usami, R. Halomicroarcula pellucidagen nov. sp. nov. a non-pigmented, transparent-colony-forming, halophilic archaeonisolated from solar salt. Int. J. Syst. Evol. Microbiol. 2013, 63, 3556–3562. [Google Scholar] [CrossRef] [Green Version]
  72. Makhdoumi-Kakhki, A.; Amoozegar, M.A.; Ventosa, A. Salinibacter iranicus sp. nov. and Salinibacter luteus sp. nov. isolated from a salt lake, and emended descriptions of the genus Salinibacter and of Salinibacter ruber. Int. J. Syst. Evol. Microbiol. 2012, 62, 1521–1527. [Google Scholar] [CrossRef] [Green Version]
  73. Abdeljabbar, H.; Cayol, J.L.; Hania, W.B.; Boudabous, A.; Sadfi, N.; Fardeau, M.L. Halanaerobium sehlinense sp. nov. an extremely halophilic, fermentative, strictly anaerobic bacterium fromsediments of the hypersaline lake Sehline Sebkha. Int. J. Syst. Evol. Microbiol. 2013, 63, 2069–2074. [Google Scholar] [CrossRef] [PubMed]
  74. Amoozegar, M.A.; Bagheri, M.; Didari, M.; Fazeli, S.A.S.; Schumann, P.; Sanchez-Porro, C.; Ventosa, A. Saliterribacillus persicus gen. nov. sp. nov. a moderately halophilic bacterium isolatedfrom a hypersaline lake. Int. J. Syst. Evol. Microbiol. 2013, 63, 345–351. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  75. Amoozegar, M.A.; Makhdoumi-Kakhki, A.; Ramezani, M.; Nikou, M.M.; Fazeli, S.A.S.; Schumann, P.; Ventosa, A. Limimonas halophila gen. nov. sp. nov. an extremely halophilic bacterium in the family Rhodospirillaceae. Int. J. Syst. Evol. Microbiol. 2013, 63, 1562–1567. [Google Scholar] [CrossRef] [PubMed]
  76. Amoozegar, M.A.; Bagheri, M.; Makhdoumi-Kakhki, A.; Didar, M.; Schumann, P.; Nikou, M.M.; Sánchez-Porro, C.; Ventosa, A. Aliicoccus persicus gen. nov. sp. nov. a halophilic member of the Firmicutes isolated from a hypersaline lake. Int. J. Syst. Evol. Microbiol. 2014, 64, 1964–1969. [Google Scholar] [CrossRef]
  77. Cui, H.L.; Yang, X.; Zhou, Y.G.; Liu, H.C.; Zhou, P.J.; Dyall-Smith, M.L. Halobellus limi sp. nov. and Halobellus salinus sp. nov. isolated from two marine solar salterns. Int. J. Syst. Evol. Microbiol. 2012, 62, 1307–1313. [Google Scholar] [CrossRef]
  78. Wang, S.; Sun, L.; Wei, D.; Zhou, B.; Zhang, J.; Gu, X.; Jiang, S. Bacillus daqingensis sp. nov. a halophilic, alkaliphilic bacterium isolated from Saline-sodic soil in Daqing, China. J. Microbiol. 2014, 52, 548–553. [Google Scholar] [CrossRef]
  79. Liu, W.; Yang, S.S. Oceanobacillus aidingensis sp. nov. a moderately halophilic bacterium. Antonie Van Leeuwenhoek 2014, 105, 801–808. [Google Scholar] [CrossRef] [Green Version]
  80. León, M.J.; Fernández, A.B.; Ghai, R.; Sánchez-Porro, C.; Rodriguez-Valera, F.; Ventosa, A. Frommetagenomics to pure culture: Isolation and characterization of the moderately Halophilic bacterium Spiribacter salinus gen. nov. sp. nov. Appl. Environ. Microbiol. 2014, 80, 3850–3857. [Google Scholar] [CrossRef] [Green Version]
  81. Miao, C.; Jia, F.; Wan, Y.; Zhang, W.; Lin, M.; Jin, W. Halomonas huangheensis sp. nov. a moderatelyhalophilic bacterium isolated from a saline–alkali soil. Int. J. Syst. Evol. Microbiol. 2014, 64, 915–920. [Google Scholar] [CrossRef]
  82. Parada-Pinilla, M.P.; Díaz-Cárdenas, C.; López, G.; Díaz-Riaño, J.I.; Gonzalez, L.N.; Restrepo, S.; Baena, S. Salifodinibacter halophilus gen. nov. sp. nov. a halophilic gammaproteobacterium in the family Salinisphaeraceae isolated from a salt mine in the Colombian Andes. Int. J. Syst. Evol. Microbiol. 2020, 70, 004490. [Google Scholar] [CrossRef]
  83. Kushwaha, B.; Jadhav, I.; Jadhav, K. Halomonas sambharensis sp. nov. a Moderately Halophilic Bacterium Isolated from the Saltern Crystallizer Ponds of the Sambhar Salt Lake in India. Curr. Microbiol. 2020, 77, 1125–1134. [Google Scholar] [CrossRef] [PubMed]
  84. Wang, Y.; Jiang, G.Q.; Lin, H.P.; Sun, P.; Zhang, H.Y.; Lu, D.M.; Tang, S.K. Lentibacillus saliphilus. sp. nov. a moderately halophilic bacterium isolated from a saltern in Korea. Arch. Microbiol. 2020, 203, 621–627. [Google Scholar] [CrossRef] [PubMed]
  85. Khan, S.A.; Zununi Vahed, S.; Forouhandeh, H.; Tarhriz, V.; Chaparzadeh, N.; Hejazi, M.A.; Hejazi, M.S. Halomonas urmiana sp. nov. a moderately halophilic bacterium isolated from Urmia Lake in Iran. Int. J. Syst. Evol. Microbiol. 2020, 70, 2254–2260. [Google Scholar] [CrossRef] [PubMed]
  86. Yoo, Y.; Lee, H.; Kwon, B.O.; Khim, J.S.; Baek, S.; Pathiraja, D.; Kim, J.J. Marinobacter halodurans sp. nov. a halophilic bacterium isolated from sediment of a salt flat. Int. J. Syst. Evol. Microbiol. 2020, 70, 6294–6300. [Google Scholar] [CrossRef] [PubMed]
  87. Cho, G.Y.; Whang, K.S. Aliifodinibius saliphilus sp. nov. a moderately halophilic bacterium isolated from sediment of a crystallizing pond of a saltern. Int. J. Syst. Evol. Microbiol. 2020, 70, 358–363. [Google Scholar] [CrossRef]
  88. Saralov, A.; Kuznetsov, B.; Reutskikh, E.; Baslerov, R.; Panteleeva, A.; Suzina, N. Arhodomonasrecens sp. nov. a halophilic alkane-utilizing hydrogen-oxidizing bacterium from the brines offlotation enrichment of potassium minerals. Microbiology 2012, 81, 582–588. [Google Scholar] [CrossRef]
  89. Mukhtar, S.; Zareen, M.; Khaliq, Z.; Mehnaz, S.; Malik, K.A. Phylogenetic analysis of halophyte- associated rhizobacteria and effect of halotolerant and halophilic phosphate-solubilizing biofertilizers on maize growth under salinity stress conditions. J. Appl. Microbiol. 2020, 128, 556–573. [Google Scholar] [CrossRef]
  90. Edbeib, M.F.; Wahab, R.A.; Huyop, F. Halophiles: Biology, adaptation, and their role in decontamination of hypersaline environments. World J. Microbiol. Biotechnol. 2016, 32, 135. [Google Scholar] [CrossRef]
  91. Nath, A. Insights into the sequence parameters for halophilicadaptation. Amino Acids 2016, 48, 751–762. [Google Scholar] [CrossRef]
  92. Anbu, P.; Hur, B.K. Isolation of an organic solvent-tolerantbacterium Bacillus licheniformis PAL05 that is able to secretesolvent-stable lipase. Biotechnol. Appl. Biochem. 2014, 61, 528–534. [Google Scholar] [CrossRef]
  93. Petrovic, U.; Cimerman, N.; Plemenitas, A. Cellular responses to environmental salinity in the halophilic black yeast Hortaea werneckii. Mol. Microbiol. 2004, 45, 665–672. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  94. Moghaddam, J.A.; Boehringer, N.; Burdziak, A.; Kunte, H.J.; Galinski, E.A.; Schäberle, T.F. Different strategies ofosmoadaptation in the closely related marine myxobacteria Enhygromyxa salina SWB007 and Plesiocystis pacifica SIR-1. Microbiology 2016, 162, 651–661. [Google Scholar] [CrossRef] [PubMed]
  95. Tanimura, K.; Matsumoto, T.; Nakayama, H.; Tanaka, T.; Kondo, A. Improvement of ectoine productivity by using sugar transporter-overexpressing Halomonas elongate. Enzyme Microb. Technol. 2016, 89, 63–68. [Google Scholar] [CrossRef] [PubMed]
  96. Youssef, N.H.; Savage-Ashlock, K.N.; McCully, A.L.; Luedtke, B.; Shaw, E.I.; Hoff, W.D.; Elshahed, M.S. Trehalose/2-sulfotrehalose biosynthesis and glycine-betaine uptake are widely spread mechanisms for osmoadaptation in the Halobacteriales. ISME J. 2014, 8, 636–649. [Google Scholar] [CrossRef]
  97. Knief, C.; Delmotte, N.; Chaffron, S.; Stark, M.; Innerebner, G.; Wassmann, R.; von Mering, C.; Varholt, J.A. Metaproteogenomic analysis of microbial communities in the phyllosphere and rhizosphere of rice. ISME J. 2012, 6, 1378–1390. [Google Scholar] [CrossRef] [Green Version]
  98. Karan, R.; Capes, M.D.; Das Sarma, S. Function andbiotechnology of extremophilic enzymes in low water activity. Aquat. Biosyst. 2012, 8, 4–10. [Google Scholar] [CrossRef] [Green Version]
  99. Ates, O.; Toksoy, E.; Arga, K.Y. Genome-scalereconstruction of metabolic network for a halophilic extremophile Chromohalobacter salexigens DSM 3043. BMC Syst. Biol. 2011, 5, 12. [Google Scholar] [CrossRef] [Green Version]
  100. Ying, X.; Liu, Y.; Xu, B.; Wang, D.; Jiang, W. Characterization and application of Halomonas shantousis SWA25, a halotolerant bacterium with multiple biogenic aminedegradation activity. Food Add. Cont. 2016, 33, 674–682. [Google Scholar]
  101. Ciulla, R.A.; Diaz, M.R.; Taylor, B.F.; Roberts, M.F. Organic osmolytes in aerobic bacteria from mono lake, an alkaline, moderately hypersaline environment. Appl. Environ. Microbiol. 1999, 63, 220–226. [Google Scholar] [CrossRef] [Green Version]
  102. Rajan, A.L.; Joseph, T.C.; Thampuran, N.; James, R.; Ashok, K.K.; Viswanathan, C.; Bansal, K.C. Cloning and heterologous expression of ectoine biosynthesis genes from Bacillus halodurans in Escherichia coli. Biotechnol. Lett. 2008, 30, 1403–1407. [Google Scholar] [CrossRef]
  103. Attar, N. A new phylum for methanogens. Nat. Rev. Microbiol. 2015, 13, 739–745. [Google Scholar] [CrossRef]
  104. Sorokin, D.Y.; Abbas, B.; Erik, V.Z.; Muyzer, G. Isolation and characterization of an obligately chemolithoautotrophic Halothiobacillus strain capable of growth on thiocyanate as anenergy source. FEMS Microbiol. Lett. 2014, 354, 69–74. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  105. Jha, M.; Chourasia, S.; Sinha, S. Microbial consortium for sustainable rice production. Agroecol. Sustain. Food Syst. 2013, 37, 340–362. [Google Scholar] [CrossRef]
  106. Davis, P.J. The plant hormones: Their nature, Occurrence and functions. In Plant Hormones; Davis, P.J., Ed.; Springer: Dordrecht, The Netherlands, 2004. [Google Scholar]
  107. Selvakumar, G.; Panneerselvam, P.; Ganeshamurthy, A.N. Bacterial mediated alleviation of abiotic stress in crops. In Bacteria in Agrobiology: Stress Management; Maheshwari, D.K., Ed.; Springer: Berlin/Heidelberg, Germany, 2012; pp. 205–223. [Google Scholar]
  108. Sagar, A.; Sayyed, R.Z.; Ramteke, P.W.; Sharma, S.; Marraiki, N.; Elgorban, A.M.; Syed, A. ACC deaminase and antioxidant enzymes producing halophilic Enterobacter sp. PR14 promotes the growth of rice and millets under salinity stress. Physiol. Mol. Biol. Plants 2020, 26, 1847–1854. [Google Scholar] [CrossRef]
  109. Parida, A.K.; Das, A.B. Salt tolerance and salinity effects on plants: A review. Ecotoxicol. Environ. Saf. 2005, 60, 324–349. [Google Scholar] [CrossRef]
  110. Hayat, R.; Ali, S.; Amara, U.; Khalid, R.; Ahmed, I. Soil beneficial bacteria and their role in plantgrowth promotion: A review. Ann. Microbiol. 2010, 60, 579–598. [Google Scholar] [CrossRef]
  111. Diby, P.; Sarma, Y.R.; Srinivasan, V.; Anandaraj, M. Pseudomonas fluorescense mediated vigourin black pepper (Piper nigrum L.) under green house cultivation. Ann. Microbiol. 2005, 55, 171–174. [Google Scholar]
  112. Upadhyay, S.K.; Singh, J.S.; Singh, D.P. Exo-polysaccharide-producing plant growth-promotingrhizobacteria salinity condition. Pedosphere 2011, 21, 214–222. [Google Scholar] [CrossRef]
  113. Bano, A.; Fatima, M. Salt tolerance in Zea mays L. following inoculation with Rhizobium and Pseudomonas. Biol. Fertil. Soils 2009, 45, 405–413. [Google Scholar] [CrossRef]
  114. Baldani, J.L.; Reis, V.M.; Baldani, V.L.D.; Dobereiner, J. A brief story of nitrogen fixation in sugarcane—Reasons for success in Brazil. Funct. Plant Biol. 2000, 29, 417–423. [Google Scholar] [CrossRef]
  115. Del Rio, L.A.; Corpas, F.J.; Sandalio, L.M.; Palma, J.M.; Barroso, J.B. Plant peroxisomes, reactiveoxygen metabolism and nitric oxide. IUBMB Life 2003, 55, 71–81. [Google Scholar] [CrossRef] [PubMed]
  116. Bor, M.; Ozdemir, F.; Turkan, I. The effect of salt stress on lipid peroxidation and antioxidantsin leaves of sugar beet Beta vulgaris L. and wild beet Beta maritime L. Plant Sci. 2003, 164, 77–84. [Google Scholar] [CrossRef]
  117. Miller, G.; Susuki, N.; Ciftci-Yilmaz, S.; Mittler, R. Reactive oxygen species homeostasis andsignalling during drought and salinity stresses. Plant Cell Environ. 2010, 33, 453–467. [Google Scholar] [CrossRef] [PubMed]
  118. Vaishnav, A.; Kumari, S.; Jain, S.; Varma, A.; Tuteja, N.; Choudhary, D.K. PGPR-mediated expressionof salt tolerance gene in soybean through volatiles under sodium nitroprusside. J. Basic Microbiol. 2016, 56, 1274–1288. [Google Scholar] [CrossRef]
  119. Santoyo, G.; Urtis-Flores, C.A.; Loeza-Lara, P.D.; Orozco-Mosqueda, M.; Glick, B.R. Rhizosphere colonization determinants by plant growth-promoting rhizobacteria (PGPR). Biology 2021, 10, 475. [Google Scholar] [CrossRef]
  120. Neilands, J.B. Siderophores: Structure and function of microbial iron transport compounds. J. Biol. Chem. 1995, 270, 26723–26726. [Google Scholar] [CrossRef] [Green Version]
  121. Jha, B.; Gontia, I.; Hartmann, A. The roots of the halophyte Salicornia brachiata are a source of new halotolerant diazotrophic bacteria with plant growth-promoting potential. Plant Soil 2012, 356, 265–277. [Google Scholar] [CrossRef]
  122. Mukhtar, S.; Malik, K.A.; Mehnaz, S. Osmoadaptation in halophilic bacteria and archaea. Res. J. Biotechnol. 2020, 15, 154–161. [Google Scholar]
  123. Razzaghi Komaresofla, B.; Alikhani, H.A.; Etesami, H.; Khoshkholgh-Sima, N.A. Improved growth and salinity tolerance of the halophyte Salicornia sp. by co–inoculation with endophytic and rhizosphere bacteria. Appl. Soil Ecol. 2019, 138, 160–170. [Google Scholar] [CrossRef]
  124. Kharangate-Lad, A.; Bhosle, S. Studies on siderophore and pigment produced by an adhered bacterial strain Halobacillus trueperi MXM-16 from the mangrove ecosystem of Goa, India. Indian J. Microbiol. 2016, 56, 461–466. [Google Scholar] [CrossRef] [Green Version]
  125. Kuzyk, S.B.; Hughes, E.; Yurkov, V. Discovery of Siderophore and Metallophore Production in the Aerobic Anoxygenic Phototrophs. Microorganisms 2021, 9, 959. [Google Scholar] [CrossRef] [PubMed]
  126. Borde, M.; Dudhane, M.; Jite, P. Growth photosynthetic activity and antioxidant responses of mycorrhizal and non-mycorrhizal bajra (Pennisetum glaucum) crop under salinity stress condition. Crop Prot. 2011, 30, 265–271. [Google Scholar] [CrossRef]
  127. Gopal, S.; Chandrasekaran, M.; Shagol, C.; Kim, K.; Sa, T. Spore associated bacteria (SAB) of arbuscular mycorrhizal fungi (AMF) and plant growth promoting rhizobacteria (PGPR) increase nutrient uptake and plant growth under stress conditions. Korean J. Soil Sci. Fertil. 2012, 45, 582–592. [Google Scholar] [CrossRef] [Green Version]
  128. Smith, S.E.; Jakobsen, I.; Grønlund, M.; Smith, F.A. Roles of arbuscular mycorrhizas in plant phosphorus nutrition: Interactions between pathways of phosphorus uptake in arbuscular mycorrhizal roots have important implications for understanding and manipulating plant phosphorus acquisition. Plant Physiol. 2011, 156, 1050–1057. [Google Scholar] [CrossRef] [Green Version]
  129. Bharti, N.; Barnawal, D.; Awasthi, A.; Yadav, A.; Kalra, A. Plant growth promoting rhizobacteria alleviate salinity induced negative effects on growth, oil content and physiological status in Mentha arvensis. Acta Physiol. Plant. 2014, 36, 45–60. [Google Scholar] [CrossRef]
  130. Miransari, M.; Bahrami, H.A.; Rejali, F.; Malakouti, M.J. Using arbuscular mycorrhiza to alleviate the stress of soil compaction on wheat (Triticum aestivum L.) growth. Soil Biol. Biochem. 2008, 40, 1197–1206. [Google Scholar] [CrossRef]
  131. Miransari, M. Contribution of arbuscular mycorrhizal symbiosis to plant growth under different types of soil stress. Plant Biol. 2010, 12, 563–569. [Google Scholar] [CrossRef]
  132. Kang, S.M.; Khan, A.L.; Waqas, M.; You, Y.H.; Kim, J.H.; Kim, J.G.; Lee, I.J. Plant growth-promoting rhizobacteria reduce adverse effects of salinity and osmotic stress by regulating phytohormones and antioxidants in Cucumis sativus. J. Plant Interact. 2014, 9, 673–682. [Google Scholar] [CrossRef] [Green Version]
  133. Liu, Y.; Johnson, N.C.; Mao, L.; Shi, G.; Jiang, S.; Ma, X.; Feng, H. Phylogenetic structure of arbuscular mycorrhizal community shifts in response to increasing soil fertility. Soil Biol. Biochem. 2015, 89, 196–205. [Google Scholar] [CrossRef] [Green Version]
  134. Mardukhi, B.; Rejali, F.; Daei, G.; Ardakani, M.R.; Malakouti, M.J.; Miransari, M. Mineral uptake of mycorrhizal wheat (Triticum aestivum L.) under salinity stress. Commun. Soil Sci. Plant Anal. 2015, 46, 343–357. [Google Scholar] [CrossRef]
  135. Ramos, A.C.; Façanha, A.R.; Palma, L.M.; Okorokov, L.A.; Cruz, Z.; Silva, A.G.; Santos, W.O. An outlook on ion signaling and ionome of mycorrhizal symbiosis. Braz. J. Plant Physiol. 2011, 23, 79–89. [Google Scholar] [CrossRef]
  136. Hajiboland, R.; Aliasgharzadeh, N.; Laiegh, S.F.; Poschenrieder, C. Colonization with arbuscular mycorrhizal fungi improves salinity tolerance of tomato (Solanum lycopersicum L.) plants. Plant Soil 2010, 331, 313–327. [Google Scholar] [CrossRef]
  137. Aroca, R.; Ruiz-Lozano, J.M.; Zamarreño, Á.M.; Paz, J.A.; García-Mina, J.M.; Pozo, M.J.; López-Ráez, J.A. Arbuscular mycorrhizal symbiosis influences strigolactone production under salinity and alleviates salt stress in lettuce plants. J. Plant Physiol. 2013, 170, 47–55. [Google Scholar] [CrossRef] [PubMed]
  138. Rai, M.K.; Kalia, R.K.; Singh, R.; Gangola, M.P.; Dhawan, A.K. Developing stress tolerant plants through in vitro selection—An overview of the recent progress. Environ. Exp. Bot. 2011, 71, 89–98. [Google Scholar] [CrossRef]
  139. Jiang, M.; Zhang, J. Water stress-induced abscisic acid accumulation triggers the increased generation of reactive oxygen species and up-regulates the activities of antioxidant enzymes in maize leaves. J. Exp. Bot. 2002, 53, 2401–2410. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  140. Nunez, M.; Mazzafera, P.; Mazorra, L.M.; Siqueira, W.J.; Zullo, M.A.T. Influence of a brassinosteroid analogue on antioxidant enzymes in rice grown in culture medium with NaCl. Biol. Plant. 2003, 47, 67–70. [Google Scholar] [CrossRef]
  141. Huang, Z.; He, C.X.; He, Z.Q.; Zou, Z.R.; Zhang, Z.B. The effects of arbuscular mycorrhizal fungi on reactive oxyradical scavenging system of tomato under salt tolerance. Agric. Sci. China 2010, 9, 1150–1159. [Google Scholar] [CrossRef]
  142. Al-Khaliel, A.S. Effect of salinity stress on mycorrhizal association and growth response of peanut infected by Glomus mosseae. Plant Soil Environ. 2010, 56, 318–324. [Google Scholar] [CrossRef] [Green Version]
  143. Sannazzaro, A.I.; Echeverría, M.; Albertó, E.O.; Ruiz, O.A.; Menéndez, A.B. Modulation of polyamine balance in Lotus glaber by salinity and arbuscular mycorrhiza. Plant Physiol. Biochem. 2007, 45, 39–46. [Google Scholar] [CrossRef]
  144. Datta, P.; Kulkarnni, M.V. Arbuscular mycorrhizal colonization enhances biochemical status and mitigates adverse salt effect on two legumes. Not. Sci. Biol. 2014, 6, 381–393. [Google Scholar] [CrossRef] [Green Version]
  145. Rillig, M.C. Arbuscular mycorrhizae, glomalin, and soil aggregation. Can. J. Soil Sci. 2004, 84, 355–363. [Google Scholar] [CrossRef] [Green Version]
  146. Rillig, M.C.; Wright, S.F.; Eviner, V.T. The role of arbuscular mycorrhizal fungi and glomalin in soil aggregation: Comparing effects of five plant species. Plant Soil 2002, 238, 325–333. [Google Scholar] [CrossRef]
  147. Borie, F.; Rubio, R.; Morales, A. Arbuscular mycorrhizal fungi and soil aggregation. Rev. Cienc. Suelo Nutr. Veg. 2008, 8, 9–18. [Google Scholar] [CrossRef]
  148. Liu, S.; Guo, X.; Feng, G.; Maimaitiaili, B.; Fan, J.; He, X. Indigenous arbuscular mycorrhizal fungi can alleviate salt stress and promote growth of cotton and maize in saline fields. Plant Soil 2016, 398, 195–206. [Google Scholar] [CrossRef]
  149. Hashem, A.; Alqarawi, A.A.; Radhakrishnan, R.; Al-Arjani, A.B.F.; Aldehaish, H.A.; Egamberdieva, D.; Abd-Allah, E.F. Arbuscular mycorrhizal fungi regulate the oxidative system, hormones and ionic equilibrium to trigger salt stress tolerance in Cucumis sativus L. Saudi J. Biol. Sci. 2018, 25, 1102–1114. [Google Scholar] [CrossRef]
  150. Khalloufi, M.; Martínez-Andújar, C.; Lachaâl, M.; Karray-Bouraoui, N.; Pérez-Alfocea, F.; Albacete, A. The interaction between foliar GA3 application and arbuscular mycorrhizal fungi inoculation improves growth in salinized tomato (Solanum lycopersicum L.) plants by modifying the hormonal balance. J. Plant Physiol. 2017, 214, 134–144. [Google Scholar] [CrossRef]
  151. Porcel, R.; Redondo-Gómez, S.; Mateos-Naranjo, E.; Aroca, R.; Garcia, R.; Ruiz-Lozano, J.M. Arbuscular mycorrhizal symbiosis ameliorates the optimum quantum yield of photosystem II and reduces non-photochemical quenching in rice plants subjected to salt stress. J. Plant Physiol. 2015, 185, 75–83. [Google Scholar] [CrossRef]
  152. Hajiboland, R.; Dashtebani, F.; Aliasgharzad, N. Physiological responses of halophytic C4 grass Aeluropus littoralis to salinity and arbuscular mycorrhizal fungi colonization. Photosynthetica 2015, 53, 572–584. [Google Scholar] [CrossRef]
  153. Giri, B.; Kapoor, R.; Mukerji, K.G. Improved tolerance of Acacia nilotica to salt stress by arbuscular mycorrhiza, Glomus fasciculatum may be partly related to elevated K/Na ratios in root and shoot tissues. Microb. Ecol. 2007, 54, 753–760. [Google Scholar] [CrossRef]
  154. Jixiang, L.; Wang, Y.; Sun, S.; Mu, C.; Yan, X. Effects of arbuscular mycorrhizal fungi on the growth, photosynthesis and photosynthetic pigments of Leymus chinensis seedlings under salt-alkali stress and nitrogen deposition. Sci. Total Environ. 2017, 576, 234–241. [Google Scholar]
  155. Venkataraman, G.S. Blue-Green Algae for Rice Production: A Manual for Its Promotion (No. 46); Food and Agriculture Org.: Rome, Italy, 1981. [Google Scholar]
  156. Kaushik, B.D.; Subhashinim, D. Amelioration of salt-affected soils with blue-green algae. II. Improvement in soil properties. Proc. Ind. Natl. Sci. Acad. 1985, 51, 380–389. [Google Scholar]
  157. Singh, V.; Singh, D.V. Cyanobacteria modulated changes and its impact on bioremediation of saline-alkaline soils. Bangladesh J. Bot. 2015, 44, 653–658. [Google Scholar] [CrossRef]
  158. Weralupitiya, C.; Wanigatunge, R.P.; Gunawardana, D.; Vithanage, M.; Magana-Arachchi, D. Cyanotoxins uptake and accumulation in crops: Phytotoxicity and implications on human health. Toxicon 2022, 211, 21–35. [Google Scholar] [CrossRef] [PubMed]
  159. Ladha, J.K.; Reddy, P.M. Extension of nitrogen fixation to rice: Necessity and possibilities. Geol. J. 1995, 35, 363–372. [Google Scholar] [CrossRef]
  160. Singh, R.N. Role of Blue-Green Algae in Nitrogen Economy of Indian Agriculture; Indian Council of Agricultural Research: New Delhi, India, 1961. [Google Scholar]
  161. Pandey, K.D.; Shukla, P.N.; Giri, D.D.; Kashyap, A.K. Cyanobacteria in alkaline soil and the effect of cyanobacteria inoculation with pyrite amendments on their reclamation. Biol. Fertil. Soils 2005, 41, 451–457. [Google Scholar] [CrossRef]
  162. Jaiswal, P.; Kashyap, A.K.; Prasanna, R.; Singh, P.K. Evaluating the potential of N. calcicola and its biocarbonate resistant mutant as bioameleorating agents for ‘usar’ soil. Ind. J. Microbiol. 2010, 50, 12–18. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  163. Murtaza, B.; Murtaza, G.; Zia-ar-Rehman, M.; Ghafoor, A.; Abubakar, S.; Sabir, M. Reclamation of salt affected soils using amendments and growing wheat crop. Soil Environ. 2011, 30, 130–136. [Google Scholar]
  164. Hussain, S.; Shaukat, M.; Ashraf, M.; Zhu, C.; Jin, Q.; Zhang, J. Salinity stress in arid and semi-arid climates: Effects and management in field crops. In Climate Change and Agriculture; Hussain, S., Ed.; IntechOpen: London, UK, 2009; pp. 1–26. [Google Scholar]
  165. Valencia-Cantero, E.; Hernández-Calderón, E.; Velázquez-Becerra, C.; López-Meza, J.E.; Alfaro-Cuevas, R.; López-Bucio, J. Role of dissimilatory fermentative iron-reducing bacteria in Fe uptake by common bean (Phaseolus vulgaris L.) plants grown in alkaline soil. Plant Soil. 2007, 291, 263–273. [Google Scholar] [CrossRef]
  166. Sarkar, A.; Ghosh, P.K.; Pramanik, K.; Mitra, S.; Soren, T.; Pandey, S.; Mondal, M.H.; Maiti, T.K. A halotolerant Enterobacter sp. displaying ACC deaminase activity promotes rice seedling growth under salt stress. Res. Microbiol. 2018, 169, 20–32. [Google Scholar] [CrossRef]
  167. Han, D.; Wang, L.; Luo, Y. Isolation, identification, and the growth promoting effects of two antagonistic actinomycete strains from the rhizosphere of Mikania micrantha Kunth. Microbiol. Res. 2018, 208, 1–11. [Google Scholar] [CrossRef]
  168. Schoenborn, L.; Yates, P.S.; Grinton, B.E.; Hugenholtz, P.; Janssen, P.H. Liquid serial dilution is inferior to solid media for isolation of cultures representative of the phylum-level diversity of soil bacteria. Appl. Environ. Microbiol. 2004, 70, 4363–4366. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  169. Whipps, J.M. Microbial interactions and biocontrol in the rhizosphere. J. Exp. Bot. 2001, 52, 487–511. [Google Scholar] [CrossRef] [PubMed]
  170. Ilangumaran, G.; Smith, D.L. Plant Growth Promoting Rhizobacteria in Amelioration of Salinity Stress: A Systems Biology Perspective. Front. Plant Sci. 2017, 8, 1768. [Google Scholar] [CrossRef] [PubMed]
  171. Obledo, E.N.; Barraga’n-Barraga’n, L.B.; Gutie’rrez-Gonza’lez, P.; Ramı’rez-Herna’ndez, B.C.; Ramı’rez, J.J.; Rodrı’guez-Garay, B. Increased photosyntethic efficiency generated by fungal symbiosis in Agave victoria-reginae. Plant Cell Tissue Organ Cult. 2003, 74, 237–241. [Google Scholar] [CrossRef]
  172. Kumar, A.; Verma, J.P. The role of microbes to improve crop productivity and soil health. In Ecological Wisdom Inspired Restoration Engineering; Achal, V., Mukherjee, A., Eds.; Springer: Singapore, 2019; pp. 249–265. [Google Scholar]
  173. Kumar, A.; Singh, S.; Gaurav, A.K.; Srivastava, S.; Verma, J.P. Plant Growth-Promoting Bacteria: Biological Tools for the Mitigation of Salinity Stress in Plants. Front. Microbiol. 2020, 11, 12–16. [Google Scholar] [CrossRef]
  174. Ahmad, M.; Zahir, Z.A.; Asghar, H.N.; Asghar, M. Inducing salt tolerance in mung bean through co-inoculation with rhizobia and plant-growth-promoting rhizobacteria containing 1-aminocyclopropane-1-carboxylate deaminase. Can. J. Microbiol. 2011, 57, 578–589. [Google Scholar] [CrossRef]
  175. Erice, G.; Ruíz-Lozano, J.M.; Zamarreñ, Á.M.; García-Mina, J.M.; Aroca, R. Transcriptomic analysis reveals the importance of JA-Ile turnover in the response of Arabidopsis plants to plant growth promoting rhizobacteria and salinity. Environ. Exp. Bot. 2017, 143, 10–19. [Google Scholar] [CrossRef] [Green Version]
  176. Ansari, F.A.; Ahmad, I.; Pichtel, J. Growth stimulation and alleviation of salinity stress to wheat by the biofilm forming Bacillus pumilus strain FAB10. Appl. Soil Ecol. 2019, 143, 45–54. [Google Scholar] [CrossRef]
  177. Bhise, K.K.; Bhagwat, P.K.; Dandge, P.B. Synergistic effect of Chryseobacteriumgleum sp. SUK with ACC deaminase activity in alleviation of salt stress and plant growth promotion in Triticum aestivum L. Biotechnology 2017, 7, 101–113. [Google Scholar]
  178. Gupta, J.; Rathour, R.; Singh, R.; Thakur, I.S. Production and characterization of extracellular polymeric substances (EPS) generated by a carbofuran degrading strain Cupriavidus sp. ISTL7. Bioresour. Technol. 2019, 282, 417–424. [Google Scholar] [CrossRef]
  179. Vurukonda, S.S.K.P.; Vardharajula, S.; Shrivastava, M. Enhancement of drought stress tolerance in crops by plant growth promoting rhizobacteria. Microbiol. Res. 2016, 184, 13–24. [Google Scholar] [CrossRef] [PubMed]
  180. Suprasanna, P.; Nikalje, G.C.; Rai, A.N. Osmolyte accumulation and implications in plant abiotic stress tolerance. In Osmolytes and Plants Acclimation to Changing Environment: Emerging Omics Technologies; Springer: New Delhi, India, 2016; pp. 1–12. [Google Scholar]
  181. Norwood, M.; Truesdale, M.R.; Richter, A.; Scott, P. Photosynthetic carbohydrate metabolism in the resurrection plant Craterostigma plantagineum. J. Exp. Bot. 2000, 51, 159–165. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  182. Volker, U.; Engelmann, S.; Maul, B.; Riethdorf, S.; Völker, A.; Schmid, R.; Mach, H.; Hecker, M. Analysis of the induction of general stress proteins of Bacillus subtilis. Microbiology 1994, 140, 741–752. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  183. Bartels, D.; Sunkar, R. Drought and salt tolerance in plants. Crit. Rev. Plant Sci. 2005, 24, 23–58. [Google Scholar] [CrossRef]
  184. Masalha, J.; Kosegarten, H.; ElmaciÖd Mengel, K. The central role of microbial activity for iron acquisition in maize and sunflower. Biol. Fert. Soils 2000, 30, 433–439. [Google Scholar] [CrossRef]
  185. Rungin, S.; Indananda, C.; Suttiviriya, P.; Kruasuwan, W.; Jaemsaeng, R.; Thamchaipenet, A. Plant growth enhancing effects by a siderophoreproducing endophytic streptomycete isolated from a Thai jasmine rice plant (Oryza sativa L. cv. KDML105). Antonie Van Leeuwenhoek 2012, 102, 463–472. [Google Scholar] [CrossRef]
  186. Ramadoss, D.; Lakkineni, V.K.; Bose, P.; Ali, S.; Annapurna, K. Mitigation of salt stress in wheat seedlings by halotolerant bacteria isolated from saline habitats. Springer Plus 2013, 2, 6. [Google Scholar] [CrossRef] [Green Version]
  187. Barriuso, J.; Solano, B.R.; Gutiérrez Mañero, F.J. Protection against pathogen and salt stress by four plant growth-promoting rhizobacteria isolated from Pinus sp. on Arabidopsis thaliana. Phytopathology 2008, 98, 666–672. [Google Scholar] [CrossRef] [Green Version]
  188. Glick, B.R. Plant growth-promoting bacteria: Mechanisms and applications. Scientifica 2012, 2012, 963401. [Google Scholar] [CrossRef] [Green Version]
  189. Olanrewaju, O.S.; Glick, B.R.; Babalola, O.O. Mechanisms of action of plant growth promoting bacteria. World J. Microbiol. Biotechnol. 2017, 33, 197. [Google Scholar] [CrossRef] [Green Version]
  190. Sharma, R.K.; Archana, G. Cadmium minimization in food crops by cadmium resistant plant growth promoting rhizobacteria. Appl. Soil Ecol. 2016, 107, 66–78. [Google Scholar] [CrossRef]
  191. Shi-Ying, Z.; Cong, F.; Yong-xia, W.; Yun-sheng, X.; Wei, X.; Xiao-Long, C. Salt-tolerant and plant growth-promoting bacteria isolated from high-yield paddy soil. Can. J. Microbiol. 2018, 64, 968–978. [Google Scholar]
  192. Jaiswal, D.K.; Verma, J.P.; Prakash, S.; Meena, V.S.; Meena, R.S. Potassium as an important plant nutrient in sustainable agriculture: A state of the art. In Potassium Solubilizing Microorganisms for Sustainable Agriculture; Springer: New Delhi, India, 2016; pp. 21–29. [Google Scholar]
  193. Santi, C.; Bogusz, D.; Franche, C. Biological nitrogen fixation in non-legume plants. Ann. Bot. 2013, 111, 743–767. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  194. Etesami, H.; Mirseyed Hosseini, H.; Alikhani, H.A. In planta selection of plant growth promoting endophytic bacteria for rice (Oryza sativa L.). J. Soil Sci. Plant Nutr. 2014, 14, 491–503. [Google Scholar] [CrossRef]
  195. Mukherjee, A.; Gaurav, A.K.; Singh, S.; Chouhan, G.K.; Kumar, A.; Das, S. Role of Potassium (K) Solubilising Microbes (KSM) in growth and induction of resistance against biotic and abiotic stress in plant: A book review. Clim. Change Environ. Sustain. 2019, 7, 212–214. [Google Scholar]
  196. Vasanthi, N.; Saleena, L.M.; Raj, S.A. Silica solubilization potential of certain bacterial species in the presence of different silicate minerals. Silicon 2018, 10, 267–275. [Google Scholar] [CrossRef]
  197. Stewart, J.; Sharpley, A. Controls on dynamics of soil and fertilizer phosphorus and sulfur. In Soil Fertility and Organic Matter as Critical Components of Production Systems (Soil Fertility); Wiley: Hoboken, NJ, USA, 1987; pp. 101–121. [Google Scholar]
  198. Qadir, M.; Schubert, S. Degradation processes and nutrient constraints in sodic soils. Land Degrad. Dev. 2002, 13, 275–294. [Google Scholar] [CrossRef]
  199. Troxler, T.G.; Ikenaga, M.; Scinto, L.; Boyer, J.N.; Condit, R.; Perez, R.; Gann, G.D.; Childers, D.L. Patterns of Soil bacteria and Canopy Community structure related to tropical peatland development. Wetlands 2012, 32, 769–782. [Google Scholar] [CrossRef]
  200. Muhammad, S.; Müller, T.; Joergensen, R.G. Decomposition of pea and maize straw in Pakistani soils along a gradient in salinity. Biol. Fertil. Soils 2006, 43, 93–101. [Google Scholar] [CrossRef]
  201. Wieder, W.R.; Boehnert, J.; Bonan, G.B. Evaluating soil biogeochemistry parameterizations in Earth system models with observations. Glob. Biogeochem. Cycles 2014, 28, 211–222. [Google Scholar] [CrossRef]
  202. Powell, J.R.; Karunaratne, S.; Campbell, C.D.; Yao, H.; Robinson, L.; Singh, B.K. Deterministic processes vary during community assembly for ecologically dissimilar taxa. Nat. Commun. 2015, 6, 8444. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  203. Hong, B.H.; Joe, M.M.; Selvakumar, G.; Kim, K.Y.; Choi, J.H.; Sa, T.M. Influence of salinity variations on exocellular polysaccharide production, biofilm formation and flocculation in halotolerant bacteria. J. Environ. Biol. 2017, 38, 657. [Google Scholar] [CrossRef]
Figure 1. Different mechanisms of adaptation in saline conditions by halophilic bacteria.
Figure 1. Different mechanisms of adaptation in saline conditions by halophilic bacteria.
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Figure 2. Salt stress tolerance by the mycorrhizal fungi compared to the non-mycorrhizal fungi.
Figure 2. Salt stress tolerance by the mycorrhizal fungi compared to the non-mycorrhizal fungi.
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Figure 3. Possible mechanisms of salt stress tolerance and salt-affected soils remediation by cyanobacteria.
Figure 3. Possible mechanisms of salt stress tolerance and salt-affected soils remediation by cyanobacteria.
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Figure 4. Different mechanisms of PGPR for plants developed under salt stress.
Figure 4. Different mechanisms of PGPR for plants developed under salt stress.
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Table 1. Halophilic bacteria species with the salt-tolerant range.
Table 1. Halophilic bacteria species with the salt-tolerant range.
Halophilic Bacterial SpeciesSalinity Range for the Growth and Development (%)References
Kangiella spongicola2–15[62]
Halanaerocella petrolearia6–26[63]
Salisediminibacterium cookie3–30[64]
Amphibacillus cookie6–26[65]
Desulfohalophilus alkaliarsenatis12.5–33[66]
Halanaerobacter jeridensis6–30[67]
Natribacillus halophilus7–23[68]
Fodinibius salinus10–15[69]
Alkalibacterium gilvum0–17.5[70]
Halomicroarcula pellucida20–30[71]
Salinibacter iranicus12–30[72]
Halanaerobium sehlinen5–30[73]
Saliterribacillus perciscus0.5–22.5[74]
Limimonas halopajila15–30[75]
Aquibacillus halophilus0.5–20[76]
Halobellus salinus15–30[77]
Bacillus daqingensis0–16[78]
Oceanicola flagellatus0–21[79]
Spiribacter salinus10–25[80]
Halomonas huangheensis1–20[81]
Salifodinibacter halophilus25[82]
Halomonas sambharensis5–8[83]
Lentibacillus saliphilus sp. nov. (type strain YIM 93176T)0–22[84]
Halomonas urmiana sp.0.5–20[85]
Marinobacter halodurans sp. nov.1–18[86]
Aliifodinibius saliphilus sp. nov.3–25[87]
Arhodomonas recens2–25[88]
Table 2. Response of the plants to AMF inoculation under salt stress conditions.
Table 2. Response of the plants to AMF inoculation under salt stress conditions.
Host PlantFungal Species (AMF)Response by PlantReferences
Cucumis sativus L. Glomus etunicatum, Glomum, intraradices, Glomus mosseaeBiomass increased, photosynthesis pigments synthesis, antioxidants enzymes increased[149]
Solanum lycopersicum L. Rhizophagus irregularisEnhanced leaf area, leaf number, root and shoot dry weight and growth harmones [150]
Oryza sativa L. Claroideoglomus etunicatumQuantum yield of PSII and photosynthetic rate increased[151]
Aeluropus littoralisClaroideoglomus etunicatumEnhanced root, shoot dry mass, soluble sugars, free amino acids[152]
Solanum lycopersicum L. Glomus intraradicesImproved dry matter, growth parameters, chlorophyll content and ions uptake[136]
Acacia niloticaGlomus fasciculateEnhanced root, shoot dry mass, P, Zn and Cu content[153]
Leymus chinensisGlomus mosseaeIncrease in the colonization rate, seedling weight, water content, P and N[154]
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Kumawat, C.; Kumar, A.; Parshad, J.; Sharma, S.S.; Patra, A.; Dogra, P.; Yadav, G.K.; Dadhich, S.K.; Verma, R.; Kumawat, G.L. Microbial Diversity and Adaptation under Salt-Affected Soils: A Review. Sustainability 2022, 14, 9280. https://doi.org/10.3390/su14159280

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Kumawat C, Kumar A, Parshad J, Sharma SS, Patra A, Dogra P, Yadav GK, Dadhich SK, Verma R, Kumawat GL. Microbial Diversity and Adaptation under Salt-Affected Soils: A Review. Sustainability. 2022; 14(15):9280. https://doi.org/10.3390/su14159280

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Kumawat, Chiranjeev, Ajay Kumar, Jagdish Parshad, Shyam Sunder Sharma, Abhik Patra, Prerna Dogra, Govind Kumar Yadav, Sunil Kumar Dadhich, Rajhans Verma, and Girdhari Lal Kumawat. 2022. "Microbial Diversity and Adaptation under Salt-Affected Soils: A Review" Sustainability 14, no. 15: 9280. https://doi.org/10.3390/su14159280

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