Search Results (621)

Bacteria adapted to elevated temperatures are commonly associated with geothermal environments and are recognized for their functional diversity. In this study, cultivable bacteria were isolated from a geothermal spring in northern Sinaloa, Mexico, and characterized through physicochemical analysis, molecular identification, growth kinetics, and functional screening. The isolates were identified as Bacillus licheniformis (strains J1, J3, and J8) and Brevibacillus borstelensis (strains J6 and J9). Growth analyses showed that, in nutrient broth at 45 °C, the evaluated strains exhibited specific growth rates ranging from 1.25 to 1.78 h⁻¹ and short doubling times between 23 and 33 min, with B. borstelensis J6 displaying the highest rate. At 50 °C, μmax values ranged from 0.77 to 1.08 h⁻¹, indicating sustained growth at elevated temperatures. Functional assays demonstrated extracellular proteolytic, amylolytic, and cellulolytic activities, mainly associated with B. licheniformis strains, in addition to tolerance to the pesticides fluazinam and benomyl. Antagonistic tests showed that B. licheniformis J8 inhibited the phytopathogenic fungi Sclerotinia sclerotiorum and Sclerotium rolfsii, while qualitative mineral solubilization assays indicated the ability of selected isolates to mobilize phosphate and potassium. These findings highlight geothermal ecosystems as valuable reservoirs of thermotolerant bacteria with enzymatic versatility and environmental relevance, supporting further molecular and process-optimization studies. Full article

Plant growth-promoting rhizobacteria (PGPR) have been collected and used to promote plant growth and enhance disease tolerance of various crops. In the current work, Pseudomonas aeruginosa CAKS2, an endophytic strain isolated from the rhizosphere of sweet orange, exhibited both growth promotion and antimicrobial activities. Under the in vitro condition, the CAKS2 showed multiple plant growth-promoting properties such as phosphate, potassium, and calcium solubilization, nitrogen fixation as well as production of siderophores, IAA, ammonia, exopolysaccharides, hydrogen cyanide, and biofilm formation. This P. aeruginosa strain inhibited the growth of different tested fungal and bacterial pathogens. Under the in vivo condition, the CAKS2 enhanced sweet orange plant growth, indicated by increases in the root and shoot lengths, the leaf number, and the total biomass. The biochemical components and the transcription levels of genes related to plant hormone biosynthesis were altered in the CAKS2-inoculated sweet orange. Under the in vivo infection of C. gloeosporioides, the CAKS2 reduced the diameter of lesions on orange leaves and harvested fruits and decreased disease severity and incidence at the whole plant level. The whole genome sequence of CAKS2 showed the presence of candidate genes involved in different molecular pathways contributing to plant-promoting and biocontrol properties. Importantly, certain changes in the expression of gene response for plant growth promotion and biocontrol were observed when the CAKS2 was exposed to sweet orange root exudates. This study highlights P. aeruginosa CAKS2 as a potential PGPR strain for enhancing plant growth and C. gloeosporioides tolerance in sweet orange and other citrus plants. Full article

Maize (Zea mays L.) cultivation is severely affected by Fusarium verticillioides, a highly adaptable systemic pathogen that causes serious yield losses, reduces grain quality, and produces toxic fumonisin, posing significant health risks to humans and livestock. A biological control approach to combating it was investigated. Streptomyces sp. BPTC-684 showed strong inhibitory activity (53.11%) against F. verticillioides BNGO-16, isolated from a diseased tissue sample. Based on physiological and biochemical characteristics, 16S rRNA gene sequencing, average nucleotide identity, and digital DNA–DNA hybridization, strain BPTC-684 is considered a candidate new species belonging to the genus Streptomyces. In silico analysis of Streptomyces sp. BPTC-684 showed that it expresses diverse biosynthetic gene clusters encoding potential bioactive compounds, notably antibiotics (kinamycin, antimycin, fuelimycins A-C, hangtaimycin, and deoxyhangtaimycin) and siderophores (desferrioxamines B and E). In addition, plant growth-promoting behaviors, such as indole-3-acetic acid production; phosphate solubilization; and the production of extracellular lytic enzymes that degrade cellulose, chitin, proteins, amylose, and xylan, were also discovered in Streptomyces sp. BPTC-684. The pot experiments demonstrated that plant height, fresh weight, and dry root weight were increased in strain BPTC-684 by 37.88%, 132.50%, and 223.81%, respectively, compared to F. verticillioides BNGO-16 on the 15th day of infection. These findings suggest that Streptomyces sp. BPTC-684 is a promising biological control agent for inhibiting fungal diseases and promoting maize growth. Full article

This review investigates the multifaceted roles of nitrogen-fixing and phosphate-mobilizing bacteria in natural ecosystems, with a particular focus on their contributions to plant growth and sustainable soil management. These microbial communities contribute substantially to nutrient cycling by converting atmospheric nitrogen into plant-available forms and mobilizing insoluble phosphorus in soil, thereby enhancing soil fertility and promoting sustainable plant productivity. This review synthesizes current knowledge on the mechanisms underlying biological nitrogen fixation, phosphate solubilization and mineralization, and the production of plant growth–promoting metabolites. Particular attention is given to plant–microbe interactions and their role in improving nutrient availability, regulating plant physiological processes, and enhancing tolerance to abiotic stresses such as salinity, drought, and heavy metal contamination. The findings underscore the ecological importance of these plant-associated microbial communities and highlight their potential applications in biofertilizer and biostimulant development for sustainable agriculture and reduced dependence on synthetic fertilizers. Full article

Baby maize (Zea mays L.) is widely cultivated across Asia due to its short growth cycle and adaptability to diverse agroecological conditions. However, its production is frequently constrained by low soil fertility, leading to the excessive use of chemical fertilizers, which in turn contributes to environmental degradation. Endophytic bacteria with the ability to fix atmospheric nitrogen and solubilize inorganic phosphate represent a sustainable alternative for improving nutrient availability. This study aimed to isolate and characterize endophytic bacteria exhibiting dual nitrogen-fixing and phosphate-solubilizing capabilities from baby maize roots. A total of ten bacterial isolates were obtained and screened using nitrogen-free Burk medium and NBRIP medium. Among these, strain CMB2 demonstrated superior functional traits. Molecular identification based on 16S rRNA gene sequencing confirmed that the isolate belongs to Bacillus stercoris. In vitro assays revealed that B. stercoris CMB2 exhibited significant nitrogenase activity, as determined by the acetylene reduction assay, and strong phosphate-solubilizing ability, indicated by a clear halo zone and a high solubilization index. These findings suggest that B. stercoris CMB2 is a promising multifunctional endophytic bacterium for enhancing nutrient availability under controlled conditions. Further validation under greenhouse and field conditions is required to assess its potential for improving plant growth and nutrient uptake in baby maize. Full article

Poor aqueous solubility remains a major limitation for the oral delivery of many active pharmaceutical ingredients (APIs). Deep eutectic solvents (DESs) exhibit remarkable drug-solubilization capacity, yet rapid precipitation upon aqueous dilution can compromise their ability to sustain supersaturation. This study investigates polymer-embedded DES (PEDES) systems as liquid supersaturating drug delivery platforms in which hydration and polymer chemistry jointly govern thermodynamic solubilization and kinetic stabilization. A choline chloride/DL-malic acid DES was prepared with 5% or 15% (w/w) water and combined with polyvinylpyrrolidone (PVP) or polyacrylic acid (PAA). Griseofulvin (GRF) was used as a precipitation-prone model drug. Structural characterization (ATR-FTIR, ¹H-NMR), equilibrium solubility measurements, storage stability studies, and non-sink dissolution testing were conducted to elucidate formulation behavior. The DES systems enhanced GRF solubility by up to ~59-fold relative to phosphate buffer (PBS, pH 6.8). Polymer incorporation produced hydration- and concentration-dependent effects. These results suggest the presence of competitive or cooperative interaction regimes. At 5% water, PEDES formulations failed to prevent recrystallization and showed limited supersaturation maintenance. In contrast, PEDES systems containing 15% water exhibited improved stability, with the formulation containing 4% PAA sustaining elevated drug concentrations for 120 min under non-sink conditions. Low-frequency solution-state ¹H-NMR confirmed stronger GRF–PAA interactions relative to PVP, supporting the role of polymer–drug association in supersaturation stabilization. These findings demonstrate that PEDES performance emerges from a hydration-dependent balance between solvent structuring and drug–polymer interactions, highlighting hydration and polymer functionality as key parameters for the rational design of liquid supersaturating systems. Full article

Saline–alkali soils suffer from severe deficiencies in available phosphorus, and externally added phosphorus is readily immobilized by metal ions in the soil. Therefore, activating inorganic phosphorus in the soil represents a significant challenge. In this study, 35 salt–alkali-tolerant bacteria were isolated from rhizosphere soils (pH 9.20–9.68). Three phosphate-solubilizing strains (HA2, HPA5, and KA1) capable of growing under severe saline–alkali stress conditions (pH 10, 5% NaCl) and possessing multiple plant growth-promoting traits (nitrogen fixation, potassium solubilization, siderophore production, and IAA secretion) were screened and co-cultured to form the microbial consortium HHK. It was hypothesized that this consortium might exhibit synergistic effects, resulting in significantly higher phosphorus solubilization capacity compared to individual strains. The results showed that under saline–alkali stress, the phosphate solubilization capacity of HHK (484.59 ± 15.79 mg/L) was significantly higher than that of any single strain (285.59 ± 12.60 mg/L). Non-targeted metabolomics and enzyme assays indicated that HHK solubilizes P via organic acids (e.g., citric, L-malic acid) and synergistically modulates core metabolic pathways, including ABC transport, TCA cycle, and glycolysis, alleviating oxidative damage and maintaining cellular homeostasis. Short-term soil incubation confirmed that HHK significantly increased available phosphorus (53.67%) and soil fertility, indicating its potential as a biofertilizer. Full article

Soil salinization is a major constraint on sustainable agriculture worldwide, highlighting the need for stress-tolerant plant growth-promoting rhizobacteria (PGPR) for salt-affected soils. A moderately halophilic and alkali-tolerant bacterium, Staphylococcus succinus NYN-1, was isolated from the rhizosphere soil of the halophyte Suaeda dendroides collected from a highly salinized site in Xinjiang, China. This study aimed to evaluate its salt–alkali tolerance and plant growth-promoting potential through integrated phenotypic characterization, pot experiments, and whole-genome analysis. NYN-1 grew over a broad salinity range [0–15% (w/v)] and pH range (6.0–11.0), and showed plant growth-promoting activities including organic phosphorus mineralization, inorganic phosphate solubilization, potassium solubilization, and NH₄⁺ production. In pot experiments under 300 mM NaCl, inoculation with NYN-1 significantly improved the growth performance of maize (Zea mays L.), cotton (Gossypium hirsutum L.), and sunflower (Helianthus annuus L.). Genome analysis identified multiple Na⁺/H⁺ antiporter-related genes and genes encoding compatible-solute transport systems that are consistent with adaptation to salt–alkali stress. The genome also harbors a broad set of genes related to phosphorus metabolism, as well as other plant growth-promoting functions, including potassium solubilization-related pathways and siderophore biosynthesis. Collectively, these findings identify S. succinus NYN-1 as a promising native halophilic PGPR candidate and a potential microbial resource for developing inoculant strategies in salt-affected agricultural systems. Full article

The Sanjiang Plain is a key black soil agricultural zone in Northeast China. The conversion of dry-lands (DL) to paddy fields (PF) alters soil aggregate phosphorus (P) fractions and microbial diversity, yet the underlying mechanisms are unclear. This study compared DL and PF (converted from DL) soils. The results showed that electrical conductivity (EC) and soil organic carbon (SOC) increased significantly after the dryland-to-paddy conversion (p < 0.05). The proportions of macroaggregates and microaggregates increased, while the silt+clay fraction declined (p < 0.05), indicating enhanced aggregate stability. Soil total P increased by 16.04%, of which 83.81%, was attributed to macroaggregate-associated P. The dominant P fractions shifted from NaOH-Po to NaOH-Pi and HCl-Pi. The land-use change also markedly altered the soil microbial community structure, leading to increased abundances of Bradyrhizobium and Pseudomonas and decreased abundances of Streptomyces and Mesorhizobium, collectively driving the transformation of P fractions. The key functional genes identified were gcd, phoD, and phnA. However, this study did not capture the temporal dynamics of P forms and microbial community structure across different stages of land-use conversion. Future research should track these dynamics throughout the conversion process to clarify the mechanisms of P evolution. Full article

Cool-season (C3) forage grasses are a cornerstone of temperate grassland systems, where improving productivity, nutritive value, and stress resilience is essential for sustainable forage production. In this context, plant growth-promoting microorganisms (PGPMs) have gained increasing attention as potential alternatives or complements to mineral and organic fertilization in grassland management. This review synthesizes current knowledge on the role of bacterial and fungal PGPM in enhancing the growth, nutrient use efficiency, and stress tolerance of C3 forage grasses, with particular emphasis on species of the genus Lolium. Available evidence indicates that PGPMs can substantially improve biomass production and plant performance under both optimal and stress conditions through a range of direct and indirect mechanisms. These include phytohormone production, nitrogen fixation, phosphate solubilization, as well as the activation of antioxidant defense systems and stabilization of plant water relations under stress. While Lolium perenne L. and Lolium multiflorum Lam. remain the most extensively studied model species, comparable growth-promoting responses have also been reported for Dactylis glomerata L., Festuca species, and Festulolium hybrids. Increasing attention is being directed toward bacterial and fungal endophytes, which may provide more persistent physiological benefits due to their close association with plant tissues. However, PGPM effects are often strongly species-, genotype-, and environment-dependent, particularly in complex grassland systems. Overall, PGPMs represent a promising tool for sustainable grassland management, although their effective application will require long-term field studies conducted under realistic meadow and pasture conditions. Full article

Salinity stress constitutes a major environmental constraint impeding crop establishment by limiting water uptake and disrupting osmotic homeostasis during seed germination and early growth. Plant growth-promoting bacteria (PGPB) offer as a sustainable and cost-effective strategy to mitigate these limitations in agricultural systems. In this study, whole-genome analysis of the salt-tolerant PGPB Priestia aryabhattai WJ45 identified its genomic potential for PGP and salinity adaptation, alongside evaluations of wheat germination under saline conditions. Genome analysis revealed that strain WJ45 harbors a coordinated set of genes associated with key plant growth-promoting traits, including exopolysaccharide production, phosphate solubilization, and siderophore biosynthesis, as well as genes involved in Na⁺/K⁺ transport and osmolyte metabolism. Consistent with these genomic predictions, germination assays demonstrated that WJ45 treatment increased the germination rate by 13.1%, under salt stress compared with the non-inoculated control, while coleoptile, radicle lengths, and fresh weight were enhanced by 17.0%, 15.7%, and 53.2%, respectively, indicating improved early seedling establishment. Collectively, these findings demonstrate that WJ45 possesses a genome-encoded capacity to facilitate crop establishment under saline conditions. While further seedling and large-scale evaluations are warranted, this study underscores the potential of this genome-informed microbial resource to enhance early plant growth and resilience in salt-affected environments. Full article

The excessive use of chemical fertilizers has depleted agricultural soils, necessitating a paradigm shift toward eco-friendly alternatives such as plant-beneficial microbes. However, the integration of plant-beneficial bacteria into global agroecosystems requires strategic and comprehensive analyses, as well as the development of optimally designed bioinocula to maximize their benefits. In this study, twenty-one rhizobacteria isolated from the maize rhizosphere were systematically screened for plant-beneficial traits, including phosphate and zinc solubilization, indole-3-acetic acid (IAA) production, and the synthesis of extracellular hydrolytic enzymes, followed by their evaluation for plant growth promotion. Among all bacterial isolates, Pseudomonas sp. NCR2 displayed the most comprehensive plant growth-promoting traits. In a pot-scale experiment, maize plants inoculated with multifaceted Pseudomonas sp. NCR2 showed significantly increased root growth, chlorophyll, soluble proteins, and phenolic contents as compared to untreated plants. This study underscores the significance of systematic screening of host-adaptive rhizobacteria for developing promising and tailored bioinocula. Furthermore, the results of this study also demonstrate the use of multifunctional biofertilizing inoculum for the systematic decrease of chemical inputs while simultaneously maintaining the crop productivity. Full article

Phosphorus (P) is an essential macronutrient for plant growth and a major limiting factor for crop productivity, especially in tropical soils characterized by low P availability and high fixation capacity. The strong dependence of modern agriculture on non-renewable phosphate fertilizers, combined with their low use efficiency, raises economic and environmental concerns and reinforces the need to improve phosphorus use efficiency (PUE) in maize. PUE is a complex trait governed by integrated morphophysiological, biochemical, and molecular mechanisms related to phosphorus acquisition, internal remobilization, metabolic reprogramming, and root system plasticity. Recent advances using omics-based approaches have substantially expanded the understanding of these mechanisms, revealing coordinated regulation of carbon and energy metabolism, phosphatase activity, redox balance, and root meristem dynamics under P-limiting conditions. In parallel, increasing evidence demonstrates the important role of phosphate-solubilizing and plant growth-promoting bacteria in enhancing P availability through organic acid secretion, enzymatic mineralization of organic P forms, and modulation of root architecture. However, despite these advances, the genetic basis of plant responsiveness to beneficial bacteria and the interaction between host genotype and microbial activity remain poorly explored. This review integrates current knowledge on phosphorus dynamics in the soil–plant system, the genetic control of PUE in maize, and the contribution of beneficial bacteria, highlighting the importance of combining classical breeding, molecular approaches, and microbial strategies to accelerate the development of maize cultivars with improved phosphorus efficiency and reduced fertilizer dependency. Full article

Phosphogypsum (PG) has the potential to elevate phosphorus levels in compost; however, it may also retard the composting maturation process, and its underlying mechanism for phosphorus activation remains unclear. In this study, sawdust was mixed with pig manure or chicken manure at a ratio of 1:4 (m:m, fresh weight) and added 10% PG as the treatment group, and added no PG as control treatment. The entire composting process lasts for 60 days. During the composting process, temperature was monitored daily, pH, electrical conductivity (EC), germination index (GI), phosphorus and its distribution were measured to monitor the composting process, and bacterial communities and predict phosphate-solubilizing genes and bacteria through the KEGG database. Pearson correlation analysis between phosphate-solubilizing bacteria and phosphorus components was conducted. The results demonstrated that (1) PG supplementation delayed the temperature rise and humification during composting, yet the final compost maturity was maintained (GI ≈ 90%). (2) PG addition increased the abundance of the ppx-gppa and phoR genes in pig manure compost, while enhancing the phnE and phoP genes in chicken manure compost. (3) In pig manure composting, Dietzia and Clostridium sensu stricto_1 were identified as key bacteria responsible for phosphorus activation, and promoting their growth favored phosphorus mobilization. (4) In chicken manure compost, Lactobacillus and Pseudomonas played crucial roles in phosphorus activation, though inhibiting their growth was found to enhance phosphorus availability. Overall, PG addition promoted phosphorus activation in compost, significantly increasing the NaHCO₃-P content in both pig manure and chicken manure composts (by 9.36 and 17.86 percentage points, respectively). Full article

Climate change-induced drought threatens the persistence of Araucaria araucana, an endangered and endemic conifer of the Southern Andes. Beneficial plant–microbe interactions may contribute to drought resilience. Here, we evaluated the effects of a root-endophytic bacterium with the capacity to produce N-acyl homoserine lactones (AHLs) on the growth and drought tolerance of A. araucana. For this, a root endophytic bacterium was isolated from A. araucana and identified as Erwinia billingiae. It was characterized for plant growth-promoting traits, and inoculated into A. araucana seedlings under drought conditions). The bacteria produced N-butyryl-L-homoserine lactone (C4-HSL) under control conditions and C4-HSL and N-hexanoyl-L-homoserine lactone (C6-HSL) under drought stress. The strain also produces indoleacetic acid, ammonia, siderophores and solubilizes phosphate. Under drought stress, non-inoculated seedlings showed marked reductions in shoot and root biomass, chlorophyll content, relative water content (RWC), and soluble sugars. In contrast, inoculated seedlings under drought displayed significantly higher shoot and root biomass, reaching levels comparable to those of well-watered controls. Chlorophyll content increased from 5.42 to 9.35 mg L⁻¹, and RWC increased from 62% to 71% in inoculated plants under drought conditions. Soluble sugar content increased from 25.74 to 36.34 mg g⁻¹ fresh weight following inoculation. Drought-induced oxidative stress was significantly alleviated in inoculated seedlings, with lower malondialdehyde and proline accumulation compared to non-inoculated drought-stressed plants. Antioxidant responses were modulated, indicating improved redox balance under water limitation. These results demonstrate that a root-endophytic bacterium with AHL production can enhance drought tolerance in A. araucana seedlings. This study provides novel evidence supporting the role of beneficial endophytes in microbiome-based strategies for conserving native forest species under climate change. Full article