Search Results (56)

Azospirillum is a well-studied genus of plant growth-promoting rhizobacteria (PGPR) and one of the most extensively researched diazotrophs. This genus can colonize rhizosphere soil and enhance plant growth and productivity by supplying essential nutrients to the host. Azospirillum–plant interactions involve multiple mechanisms, including nitrogen fixation, the production of phytohormones (auxins, cytokinins, indole acetic acid (IAA), and gibberellins), plant growth regulators, siderophore production, phosphate solubilization, and the synthesis of various bioactive molecules, such as flavonoids, hydrogen cyanide (HCN), and catalase. Thus, Azospirillum is involved in plant growth and development. The genus Azospirillum also enhances membrane activity by modifying the composition of membrane phospholipids and fatty acids, thereby ensuring membrane fluidity under water deficiency. It promotes the development of adventitious root systems, increases mineral and water uptake, mitigates environmental stressors (both biotic and abiotic), and exhibits antipathogenic activity. Biological nitrogen fixation (BNF) is the primary mechanism of Azospirillum, which is governed by structural nif genes present in all diazotrophic species. Globally, Azospirillum spp. are widely used as inoculants for commercial crop production. It is considered a non-pathogenic bacterium that can be utilized as a biofertilizer for a variety of crops, particularly cereals and grasses such as rice and wheat, which are economically significant for agriculture. Furthermore, Azospirillum spp. influence gene expression pathways in plants, enhancing their resistance to biotic and abiotic stressors. Advances in genomics and transcriptomics have provided new insights into plant-microbe interactions. This review explored the molecular mechanisms underlying the role of Azospirillum spp. in plant growth. Additionally, BNF phytohormone synthesis, root architecture modification for nutrient uptake and stress tolerance, and immobilization for enhanced crop production are also important. A deeper understanding of the molecular basis of Azospirillum in biofertilizer and biostimulant development, as well as genetically engineered and immobilized strains for improved phosphate solubilization and nitrogen fixation, will contribute to sustainable agricultural practices and help to meet global food security demands. Full article

Exploring the mechanisms by which green agricultural production reduces emissions and enhances carbon sequestration in soil can provide a scientific basis for greenhouse gas reduction and sustainable development in farmland. This study uses a combination of meta-analysis and field experiments to evaluate the impact of different agricultural management practices and climatic conditions on soil organic carbon (SOC) and the emissions of CO₂ and CH₄, as well as the role of microorganisms. The results indicate the following: (1) Meta-analysis reveals that the long-term application of organic fertilizers in green agriculture increases SOC at a rate four times higher than that of chemical fertilizers. No-till and straw return practices significantly reduce CO₂ emissions from alkaline soils by 30.7% (p < 0.05). Warm and humid climates in low-altitude regions are more conducive to soil carbon sequestration. (2) Structural equation modeling of plant–microbe–soil carbon interactions shows that plant species diversity (PSD) indirectly affects microbial biomass by influencing organic matter indicators, mineral properties, and physicochemical characteristics, thereby regulating soil carbon sequestration and greenhouse gas emissions. (3) Field experiments conducted in the typical green farming research area of Chenzhuang reveal that soils managed under natural farming absorb CH₄ at a rate three times higher than those under conventional farming, and the stoichiometric ratios of soil enzymes in the former are close to 1. The peak SOC (19.90 g/kg) in the surface soil of Chenzhuang is found near fields cultivated with natural farming measures. This study provides theoretical support and practical guidance for the sustainable development of green agriculture. Full article

Optimal dietary calcium (Ca) and phosphorus (P) requirements remain undetermined for Ningxiang pigs, a valuable indigenous Chinese breed. This study conducted a continuous feeding trial with two growth phases (grower: 30–50 kg; finisher: 50–80 kg) using fixed Ca/P ratios to systematically evaluate the effects of Ca/P levels on growth performance and mineral metabolism. A total of 180 pigs per phase were allocated to four Ca/P levels. During the grower phase, a dietary regimen of 0.83% Ca/0.67% P significantly increased the average daily feed intake (ADFI), average daily gain (ADG), and apparent total tract digestibility (ATTD) of energy and P. In the finisher phase, 0.60/0.48% Ca/P showed optimal growth performance, upregulated jejunal mineral transporters (CaSR and SLC34A2), enhanced bone mineralization (metatarsal ash content), and improved intestinal morphology (duodenal and jejunal villus height, jejunal villus surface area). This regimen also selectively enriched Peptostreptococcaceae abundance, indicating improved host–microbe interactions. Based on these findings, stage-specific nutritional strategies were recommended: 0.83% Ca/0.67% P during the grower phase and 0.60% Ca/0.48% P during the finisher phase. These protocols synergistically improve microbial ecology, intestinal function, and bone metabolism, thereby maximizing the growth potential of Ningxiang pigs. Full article

The bioavailability of heavy metals is profoundly influenced by their interactions with active soil components (microorganisms, organic matter, and iron minerals). However, the effects of urease-producing bacteria combined with organo-Fe hydroxide coprecipitates (OFCs) on Cd accumulation in wheat, as well as the mechanisms underlying these effects, remain unclear. In this study, pot experiments integrated with high-throughput sequencing were employed to investigate the impacts of the urease-producing bacterial strain TJ6, ferrihydrite (Fh), and OFCs on Cd enrichment in wheat grains, alongside the underlying soil–microbial mechanisms. The results demonstrate that the strain TJ6-Fh/OFC consortium significantly (p < 0.05) reduced (50.1–66.7%) the bioavailable Cd content in rhizosphere soil while increasing residual Cd fractions, thereby decreasing (77.4%) Cd accumulation in grains. The combined amendments elevated rhizosphere pH (7.35), iron oxide content, and electrical conductivity while reducing (14.5–21.1%) dissolved organic carbon levels. These changes enhanced soil-colloid-mediated Cd immobilization and reduced Cd mobility. Notably, the NH₄⁺ content and NH₄⁺/NO₃⁻ ratio were significantly (p < 0.05) increased, attributed to the ureolytic activity of TJ6, which concurrently alkalinized the soil and inhibited Cd uptake via competitive ion channel interactions. Furthermore, the relative abundance of functional bacterial taxa (Proteobacteria, Gemmatimonadota, Enterobacter, Rhodanobacter, Massilia, Nocardioides, and Arthrobacter) was markedly increased in the rhizosphere soil. These microbes exhibited enhanced abilities to produce extracellular polymeric substances, induce phosphate precipitation, facilitate biosorption, and promote nutrient (C/N) cycling, synergizing with the amendments to immobilize Cd. This study for the first time analyzed the effect and soil science mechanism of urease-producing bacteria combined with OFCs in blocking wheat’s absorption of Cd. Moreover, this study provides foundational insights and a practical framework for the remediation of Cd-contaminated wheat fields through microbial–organic–mineral collaborative strategies. Full article

Morel mushrooms (Morchella spp.) are prized for their nutritional and medicinal value. Despite extensive research on their cultivation, the species’ impacts on the soil microbiota and minerals remain unclear. This study systematically evaluated six Morchella species, analyzing their effects on soil physicochemical properties, microbial communities, and mineral nutrients levels. The results showed that yield varied significantly among the species, with an order of M. sextelata > M. exuberans > M. eximia > M. importuna > Mel-13 > Mel-21. Cultivation led to a consistent reduction in soil NO₃⁻-N levels, particularly in M. eximia and Mel-13 (40–50% decrease), while NH₄⁺-N levels did not change significantly, indicating mycelial nitrate preference. Mineral nutrient alterations exhibited distinct species-dependent patterns, with M. eximia showing the greatest increase in exchangeable Ca, while M. importuna and M. sextelata caused the most obvious decreases in available B. Morchella species exerted more pronounced impacts on fungal than bacterial communities, evidenced by significant reductions in alpha diversity—particularly in high-yield M. sextelata—suggesting species-specific fungal inhibition. At the phylum level, consistent depletion of Ascomycota but enrichment of Mortierellomycota were noted. Moreover, correlation analyses identified significant positive associations between morel yield and both fungal community diversity and exchangeable Ca content. This implies that Morchella species restructures soil fungal communities through nutrient competition and mineral-mediated regulation, with calcium acting as a key modulator. Overall, by elucidating the interconnected ‘Morchella species–microbe–mineral’ relationships, this study highlights Morchella species’ distinct regulation of soil microecology, providing valuable insights for the selection of optimized species like M. eximia and targeted soil management in morel cultivation. Full article

The weathering of seafloor hydrothermal sulfides is facilitated by microbial activities, yet the specific mechanisms of different sulfide types are not well understood. Previous studies have primarily been carried out under laboratory conditions, making it difficult to accurately replicate the complex in situ conditions of deep-sea hydrothermal fields. Herein, we deployed two well-characterized pyrite (Py)-dominated and chalcopyrite (Ccp)-dominated sulfide slices, which were placed 300 m from an active venting site in the Wocan-1 hydrothermal field (Carlsberg Ridge, Northwest Indian Ocean) for an 18-month in situ incubation experiment. Microscopic observations and organic matter analyses were conducted on the recovered sulfide slices to investigate the microbial weathering features of different sulfide types. Our results demonstrated that the weathering of the Py-dominated sulfide sample was primarily mediated by extracellular polymeric substances (EPSs) through indirect interactions, whereas the Ccp-dominated sulfide sample exhibited both direct microbial dissolution, resulting in the formation of distinct dissolution pits, and indirect EPS-mediated interactions. Four distinct phases of microbe–sulfide interactions were identified: approach, adsorption, stable attachment, and extensive colonization. Furthermore, the weathering products and biomineralization structures differed significantly between the two sulfide types, reflecting their different microbial colonization processes. Our study confirms that microorganisms are crucial in seafloor sulfide weathering. These findings advance our understanding of microbial-driven processes in sulfide mineral transformations and their role in marine ecosystems. Our findings are also valuable for future research on biogeochemical cycles and for developing bioremediation strategies for deep-sea mining. Full article

Ionic rare earth ore (IREO) has a high abundance of medium and heavy rare earth elements (REEs), making it a vital strategic resource for China. In this work, two typical microorganisms, Aspergillus niger and Acidithiobacillus ferrooxidans, were used to study the interaction mechanism during the bioleaching of IREO under acidic conditions. The results revealed some differences in the interaction and leaching effects of A. niger and A. ferrooxidans on ionic rare earth minerals. A. niger mainly forms rare earth complexes with rare earth ions in IREO by secreting metabolites such as organic acids, thereby promoting the release of REEs, and it has a strong adsorption capacity for Yb. A. ferrooxidans promotes the release of REEs from rare earth minerals, primarily through iron–sulfur oxidation. The differential expression of metabolic genes (e.g., gpmL, FabF, FASN) associated with major metabolite secretion indicates their correlation with the leaching process. The above results reveal the role of the typical acid-producing microorganisms A. niger and A. ferrooxidans and their metabolites in the leaching of IREO, which is valuable for understanding the interaction mechanisms between microorganisms and IREO under acidic conditions. Full article

Microbe–microbe interactions within a host drive shifts in the host’s microbiota composition, profoundly influencing host physiology, ecology, and evolution. Among these microbes, the maternally inherited endosymbiont Wolbachia is widespread in the invasive pest Liriomyza huidorbrensis (Diptera: Agromyzidae). However, its influence on the host microbiota remains largely unexplored. In the study presented herein, we investigated the bacterial communities of Wolbachia wLhui-infected (wLhui+) and -uninfected lines (wLhui−) of L. huidorbrensis using 16S rRNA gene high-throughput sequencing. For both leaf-miner lines, Bacteroidota was the dominant phylum (relative abundance: 59.18%), followed by Pseudomonadota (36.63%), Actinomycetota (2.42%), and Bacillota (0.93%). We found no significant differences in alpha-diversity indices between the wLhui+ and wLhui− lines (p > 0.05). However, principal coordinates analysis revealed significant differences in microbiota composition between the wLhui+ and wLhui− lines (PERMANOVA: p < 0.001), explaining 76.70% of the variance in microbiota composition. Correlation network analysis identified robust negative and positive associations between Wolbachia and several genera, suggesting that Wolbachia shapes microbial composition through competitive or cooperative interactions with specific taxa. Overall, our study suggests that Wolbachia plays a key role in shaping the leaf-miner microbiome, potentially affecting host fitness. Full article

The interaction between secondary phyllosilicate minerals and straw is crucial for preserving soil organic carbon (SOC) and fertility. However, the specific mechanism through which these minerals affect straw decomposition and its products in northeast China’s black soil remains unclear. In this study, montmorillonite, illite, and vermiculite were mixed with quartz sand and maize straw, inoculated with microbes, and incubated to analyze the effects of different secondary phyllosilicate minerals on the degradation of organic components in maize straw and the formation of soil humus. The results showed that montmorillonite significantly facilitated the decomposition of maize straw hemicellulose and lignin, which decreased by 95.85% and 76.38%, respectively. Conversely, vermiculite decelerated hemicellulose and lignin degradation. Regarding soil organic acids, lactic acid and malic acid were predominant, with the highest content being found after the montmorillonite treatment. Montmorillonite was the most effective in enhancing extractable humic-like substances, which increased by 71.68%. Montmorillonite increased the content of G0 (water dispersion group), G1 (sodium ion dispersion group), and G2 (sodium grinding dispersion group) complexes. The addition of secondary phyllosilicate minerals increased the organic carbon (OC) content in the G0, G1, and G2 samples, with montmorillonite demonstrating the most pronounced effect. Secondary phyllosilicate minerals increased the abundance of fungi, particularly Ascomycota, with the highest abundance being found after the montmorillonite treatment. In conclusion, our results indicated that montmorillonite facilitated the decomposition of lignocellulose in maize straw, enhanced the accumulation of humus, and promoted the formation of organic–mineral complexes. These findings provide valuable insights into the interaction between secondary phyllosilicate minerals and maize straw and have important implications for improving the quality of black soil in northeast China. Full article

The rhizosphere, a narrow region of soil surrounding plant roots, is an environment rich in microbial diversity that profoundly influences plants’ health, growth, and agricultural productivity. This microbial community, known as the rhizosphere microbiome, consists of a complex array of bacteria, fungi, archaea, and other microorganisms that engage in complex interactions with plant roots. These microorganisms contribute to nutrient cycling, mineral uptake facilitation, and protection against soil-borne pathogens, thereby promoting plant growth and resilience towards biotic and abiotic stresses. Additionally, microbial signaling molecules, including phytohormones such as auxins, cytokinin, gibberellins, ethylene, and abscisic acid, play a pivotal role in regulating these interactions by modulating plants’ responses to environmental stressors. Recent advancements in microbiomics have enabled a deeper understanding of the rhizosphere’s diversity, composition, and functions, paving the way for more sustainable agricultural practices. By harnessing the potential of the rhizosphere microbiome, innovative strategies can be developed to reduce dependency on synthetic agrochemicals, enhance soil fertility, and increase crop yields. This review discusses the diversity and mechanisms of plant–microbe interactions, focusing on the role of microbial signaling molecules, and explores their applications in promoting agricultural sustainability. The insights gained from microbiomics studies can revolutionize farming practices by reducing dependency on chemical inputs, enhancing crop productivity, and nurturing soil health and environmental sustainability. Full article

Microbes such as bacteria and fungi play important roles in nutrient cycling in soils, often leading to the bioavailability of metabolically important mineral elements such as nitrogen (N), phosphorus (P), iron (Fe), and zinc (Zn). Examples of microbes with beneficial traits for plant growth promotion include mycorrhizal fungi, associative diazotrophs, and the N₂-fixing rhizobia belonging to the α, β and γ class of Proteobacteria. Mycorrhizal fungi generally contribute to increasing the surface area of soil-root interface for optimum nutrient uptake by plants. However, when transformed into bacteroids inside root nodules, rhizobia also convert N₂ gas in air into ammonia for use by the bacteria and their host plant. Thus, nodulated legumes can meet a high proportion of their N requirements from N₂ fixation. The percentage of legume N derived from atmospheric N₂ fixation varies with crop species and genotype, with reported values ranging from 50–97%, 24–67%, 66–86% 27–92%, 50–92%, and 40–75% for soybean (Gycine max), groundnut (Arachis hypogea), mung bean (Vigna radiata), pigeon pea (Cajanus cajan), cowpea (Vigna unguiculata), and Kersting’s groundnut (Macrotyloma geocarpum), respectively. This suggests that N₂-fixing legumes require little or no N fertilizer for growth and grain yield when grown under field conditions. Even cereals and other species obtain a substantial proportion of their N nutrition from associative and endophytic N₂-fixing bacteria. For example, about 12–33% of maize N requirement can be obtained from their association with Pseudomonas, Hebaspirillum, Azospirillum, and Brevundioronas, while cucumber can obtain 12.9–20.9% from its interaction with Paenebacillus beijingensis BJ-18. Exploiting the plant growth-promoting traits of soil microbes for increased crop productivity without any negative impact on the environment is the basis of green agriculture which is done through the use of biofertilizers. Either alone or in combination with other synergistic rhizobacteria, rhizobia and arbuscular mycorrhizal (AM) fungi have been widely used in agriculture, often increasing crop yields but with occasional failures due to the use of poor-quality inoculants, and wrong application techniques. This review explores the literature regarding the plant growth-promoting traits of soil microbes, and also highlights the bottle-necks in tapping this potential for sustainable agriculture. Full article

The use of plant growth-promoting rhizobacteria presents a promising addition to conventional mineral fertilizer use and an alternative strategy for sustainable agricultural crop production. However, genotypic variations in the plant host may result in variability of the beneficial effects from these plant–microbe interactions. This study examined growth promotion effects of commercial vegetable crop cultivars of tomato, cucumber and broccoli following application with five rhizosphere bacteria. Biochemical assays revealed that the bacterial strains used possess several nutrient acquisition traits that benefit plants, including nitrogen fixation, phosphate solubilization, biofilm formation, and indole-3-acetic acid (IAA) production. However, different host cultivars displayed genotype-specific responses from the inoculations, resulting in significant (p < 0.05) plant growth promotion in some cultivars but insignificant (p > 0.05) or no growth promotion in others. Gene expression profiling in tomato cultivars revealed that these cultivar-specific phenotypes are reflected in differential expressions of defense and nutrient acquisition genes, suggesting that plants can be categorized into “microbe-friendly” cultivars (with little or no defense responses against beneficial microbes) and “microbe-hostile” cultivars (with strong defense responses). These results validate the notion that “microbe-friendly” (positive interaction with rhizosphere microbes) should be considered an important trait in breeding programs when developing new cultivars which could result in improved crop yields. Full article

As a vital component of the global carbon pool, soils in arid and semi-arid regions play a significant role in carbon sequestration. In the context of global warming, increasing temperatures and moisture levels promote the transformation of barren land into wetlands, enhancing carbon sinks. However, the overdevelopment of oases and excessive extraction of groundwater lead to the opposite effect, reducing carbon sequestration. This study examines two soil types—meadow soil (MS) and swamp soil (SS)—from Qingtu Lake, an arid lake in western China. It analyzes the sources of soil inorganic carbon, the composition and origin of dissolved organic matter (DOM), and the relationships between microbes, soil organic carbon (SOC), soil inorganic carbon (SIC), mineral composition, and soil texture. The results indicate that inorganic carbon in the study area consists of both primary carbonate minerals and secondary pedogenic carbonates. The DOM primarily consists of two components, both identified as terrestrial humic substances. In meadow soils, bacterial activity drives the weathering of plagioclase, which releases Ca²⁺ necessary for the formation of pedogenic carbonates. Plagioclase also provides colonization sites for microbes and, along with microbial activity, participates in the soil carbon cycle. Within the soil community, bacteria appear to play a more critical role than fungi. In contrast, microbial contributions to the carbon cycle in swamp soils are weaker, with minerals predominantly interacting with organic carbon to form mineral-associated organic matter, thus promoting the soil carbon cycle. These findings have important implications for understanding soil carbon sinks under different micro-ecological conditions in arid and semi-arid regions. Through targeted human intervention, it is possible to enhance carbon sequestration in these areas, contributing to the mitigation of global climate change. Full article

The increasing level of anthropogenic CO₂ in the atmosphere has made it imperative to investigate an efficient method for carbon sequestration. Geological carbon sequestration presents a viable path to mitigate greenhouse gas emissions by sequestering the captured CO₂ deep underground in rock formations to store it permanently. Geochemistry, as the cornerstone of geological CO₂ sequestration (GCS), plays an indispensable role. Therefore, it is not just timely but also urgent to undertake a comprehensive review of studies conducted in this area, articulate gaps and findings, and give directions for future research areas. This paper reviews geochemistry in terms of the sequestration of CO₂ in geological formations, addressing mechanisms of trapping, challenges, and ways of mitigating challenges in trapping mechanisms; mineralization and methods of accelerating mineralization; and the interaction between rock, brine, and CO₂ for the long-term containment and storage of CO₂. Mixing CO₂ with brine before or during injection, using microbes, selecting sedimentary reservoirs with reactive minerals, co-injection of carbonate anhydrase, and enhancing the surface area of reactive minerals are some of the mechanisms used to enhance mineral trapping in GCS applications. This review also addresses the potential challenges and opportunities associated with geological CO₂ storage. Challenges include caprock integrity, understanding the lasting effects of storing CO₂ on geological formations, developing reliable models for monitoring CO₂–brine–rock interactions, CO₂ impurities, and addressing public concerns about safety and environmental impacts. Conversely, opportunities in the sequestration of CO₂ lie in the vast potential for storing CO₂ in geological formations like depleted oil and gas reservoirs, saline aquifers, coal seams, and enhanced oil recovery (EOR) sites. Opportunities include improved geochemical trapping of CO₂, optimized storage capacity, improved sealing integrity, managed wellbore leakage risk, and use of sealant materials to reduce leakage risk. Furthermore, the potential impact of advancements in geochemical research, understanding geochemical reactions, addressing the challenges, and leveraging the opportunities in GCS are crucial for achieving sustainable carbon mitigation and combating global warming effectively. Full article

Heap bioleaching is considered to be a less energy-intensive metal-extraction technique compared to other methods, making it particularly attractive for low-grade sulfide ores. It has been successfully applied to recovery of copper, gold, and uranium from ores over decades. Despite its seemingly straightforward nature, heap bioleaching can experience failures if the ore is unsuitable or the heap leach process is not thoroughly investigated and well-developed. Therefore, multidisciplinary approaches are essential for research and development in heap bioleaching, as its performance depends on numerous processes operating across a wide range of length scales. This review focused on the current state of knowledge regarding the understanding of multi-scale mechanisms in heap bioleaching and the use of multidisciplinary approaches at different scales to develop the process. The investigation covered various scales, such as atomic and molecular, mineralogy and microbes, reaction particles, heap bioleaching units and full-scale factory production. Different approaches were employed to gain a comprehensive understanding of the microbial molecular structure and metabolism, the structure and reaction of minerals, microbial–mineral interaction, particles and aggregation states, and multiphase flow transfer, as well as laboratory experiments, modeling, industrialization, and operation optimization. We emphasized the need for collaboration among researchers from different disciplines and stress the importance of considering the coupling effects of physical, chemical, and microbiological factors when running heap bioleaching plants. Such collaboration and coupling are vital for successful implementation and optimization of heap bioleaching processes. This paper aimed to provide a comprehensive overview of current research related to heap bioleaching at different scales and disciplines, and gave implications to heap bioleaching technology development. Full article