Search Results (304)

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

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

Returning organic amendments to saline–alkali soils constitutes a key strategy for soil amelioration, as it enhances crop productivity by modulating the rhizosphere microenvironment. In this study, straw, biochar, and peat were selected as representative organic amendments, and a two-year field experiment—employing a rotational cropping system of Sesbania and Triticale—was conducted to investigate their differential regulatory effects on rhizosphere properties and root development. Results demonstrated that all three amendments induced coordinated shifts in the rhizosphere “extract–microbiota–enzymes–nutrients” nexus, concomitant with significant stimulation of root growth. The hypothesized pathways through which different organic amendments improve the rhizosphere environment vary mechanistically: straw application appears to enhance alkaline phosphatase activity and enrich phosphorus-solubilizing microorganisms; it is hypothesized that this promotes root growth by facilitating the mineralization of organic phosphorus. In contrast, peat amendment induces the most pronounced increases in esterase content and sucrase activity, and its growth-promoting effect is likely attributable to accelerated carbon and phosphorus cycling. Biochar, meanwhile, is associated with elevated catalase activity, improved potassium retention, and enhanced organic carbon sequestration; its beneficial function is postulated to stem from mitigation of oxidative stress. Collectively, this study provides initial evidence that distinct organic amendments modulate rhizosphere processes via divergent biochemical and microbial mechanisms—offering a theoretical foundation for their rational selection and application in saline–alkali soil remediation. Full article

Sustainable agricultural techniques can ensure food security around the world. Hydrogel based soilless culture is an ecological and efficient alternative compared to conventional agriculture. Here, a multi-component hydrogel (pectin, Kelcogel, and chitosan/Se hydrogel, PKCH) was prepared by synthesizing natural biomolecules to cultivate dandelion for stimulate dandelion growth and improve nutritional value. The germination percentage of dandelion on PKCH (88.89%), was significantly higher than that in traditional hydroponics and pure Kelcogel (p < 0.05). Compared with hydroponics, the long-term dandelion cultivation experiments demonstrated that the PKCH cultivation mode enhanced root vitality, further increasing the growth and yield of dandelions (shoot length: 18.36 ± 0.30 cm, root length: 9.28 ± 0.21 cm, main root diameter: 0.94 ± 0.02 cm). The hydrogel substrate was associated with improved nutrient solubilization and sustained release, which may be linked to the accumulation of low-molecular-weight organic acids in the rhizosphere. Exogenous Se was effectively assimilated and transported to the above-ground parts of dandelion, which stimulated the photosynthetic efficiency and nutritional accumulation of dandelion. The polysaccharide content of dandelion reached 69.40 ± 0.13% (expressed as glucose-equivalent total sugars), which demonstrated the potential antioxidant properties and medicinal value. Technical economic analysis revealed the cost-effectiveness of PKCH synthesis and application. This study enriches the application of hydrogels in dandelion cultivation and provides an alternative approach for cultivating dandelion in soilless environments and medicinal crop production techniques. Full article

Biochar and plant growth-promoting rhizobacteria (PGPR) are promising for coastal saline–alkali soil remediation, but their combined effect is often limited by nutrient scarcity. This study investigated whether nutrient-laden biochar (saturated with livestock wastewater) synergizes with a PGPR inoculant (Paenibacillus mucilaginosus PM12) to enhance maize productivity by reshaping the rhizosphere microbiome. A field experiment included five treatments: control (CK), sheep manure biochar alone (BC), nutrient-laden biochar (NBC), BC + PGPR (MBC), and NBC + PGPR (MNBC). The MNBC treatment showed the most pronounced improvements, increasing maize yield by 52.5% compared to CK, while reducing soil pH by 0.30 units and enhancing soil organic matter, total nitrogen, and available phosphorus. Metagenomic analysis revealed that MNBC uniquely enriched beneficial genera (e.g., Nocardioides) and saprotrophic Basidiomycota, while suppressing pathogenic Fusarium. This restructuring elevated the genetic potential for nitrogen transformation, phosphorus solubilization, and carbon metabolism. Structural equation modeling identified increased soil available phosphorus and total nitrogen as the primary direct drivers of yield enhancement. The integration of nutrient-laden biochar and PGPR creates a synergistic system that reclaims saline–alkali soil by alleviating stress, supplying nutrients, and directing the assembly of a functional microbiome. 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

The increasing reliance on chemical fertilizers has raised environmental concerns and highlighted the need for sustainable alternatives. This study aimed to (i) optimize the carrier-to-substrate ratios and moisture content during composting with potassium-solubilizing purple nonsulfur bacteria (K-PNSB) and (ii) evaluate the growth-promoting effect of the optimized biofertilizer on maize seedlings. Three K-PNSB strains (Cereibacter sphaeroides M-Sl-09, Rhodopseudomonas thermotolerans M-So-11, and Rhodopseudomonas palustris M-So-14) were used. Composting experiments were conducted using different carrier-to-substrate ratios and moisture levels with K-PNSB inoculation. Compost quality was assessed through nutrient dynamics, bacterial density, and physicochemical properties over four weeks. The results showed that the 1:1:3 substrate ratio combined with 50–60% moisture content consistently enhanced K solubilization, bacterial survival, and compost maturity indicators. Application of the optimized biofertilizer improved maize growth traits compared with the non-inoculated control. These findings demonstrate that controlling material ratios and moisture content improves compost quality and plant growth performance, providing a sustainable alternative to chemical fertilizers. This study provides a practical framework for developing sustainable K-solubilizing biofertilizers from agricultural residues. Full article

Montane forests are commonly limited by phosphorus (P) scarcity, yet Rhododendron species persist via specialized P-acquisition strategies. However, the microbial processes governing P utilization among wild Rhododendron species remain unclear. We collected soil and root samples from three wild Rhododendron species—Rhododendron latoucheae Franch. (R. latoucheae), Rhododendron fortunei Lindl. (R. fortunei) and Rhododendron simsii Planch. (R. simsii)—in a montane forest and analyzed soil P fractions, acid phosphatase activity, and fungal community traits to investigate their relationships with P cycling. The results showed significant differences in P fraction contents between non-rhizosphere and rhizosphere soils among the three species. In R. fortunei, rhizospheric NaOH-Po decreased tenfold while H₂O-Pi increased by 9.13 mg/kg, indicating a shift toward labile P. In contrast, R. latoucheae and R. simsii showed increases in moderately labile P by 32.54% and 22.09%, respectively. R. latoucheae exhibited the lowest acid phosphatase activity in non-rhizosphere soil (4.810 ± 0.560 μmol/d/g), which increased significantly in the rhizosphere. Fungal community analysis revealed a significant enrichment of Podila in the rhizosphere of R. latoucheae (10.84%) and R. simsii (9.17%), while Penicillium (6.80%), Trichoderma (3.65%) and Mortierella (5.83%) were dominant in the R. fortunei rhizosphere. R. latoucheae mineralized organic P through acid phosphatase hydrolysis driven by nutrient scarcity. R. fortunei likely mobilizes inorganic P through ericoid mycorrhizal-associated secretion of organic acids and the activity of specialized phosphate-solubilizing fungi facilitated by high substrate availability. Soil nutrients (SOC, TN, $\mathrm{N}{\mathrm{O}}_3^{-}$-N) influenced fungal abundances and indirectly shaped soil P fractions, whereas fungal taxa abundance in the rhizosphere directly drove P turnover. Our results confirm that different wild Rhododendron species employ distinct P-acquisition strategies mediated by rhizosphere fungi and enzyme activities, and provide new insights into microbial-driven P cycling in montane forests. Full article

Sustainable care of urban lawns requires methods that maintain high turf quality while reducing the use of chemical fertilizers. The objective of this three-year field study was to evaluate whether microbial inoculants can complement or partially substitute conventional fertilization (65–190 kg N·ha⁻¹, 33–35.2 kg P·ha⁻¹, and 124.5 kg K·ha⁻¹) required to maintain high turf quality in an intensively managed lawn system. The experiment was conducted in Poland on a degraded chernozem, classified as Haplic Phaeozem. A standard mixture of perennial ryegrass and fescue was evaluated under four treatments: (1) untreated control; three commercial microbial formulations: (2) StymGrass P+K, containing nutrient-solubilizing Bacillus spp.; (3) BioVitaGrass, combining Bacillus spp. with arbuscular mycorrhizal fungi (AMF); and (4) NitroGrass, containing nitrogen-fixing Azotobacter spp. with Bacillus spp. All microbial treatments improved lawn quality compared with the untreated control. Lawns receiving BioVitaGrass or NitroGrass showed the strongest responses, including denser plant cover, greener and finer leaves, reduced disease symptoms, and increased concentrations of nutrients in the plant tissue. StymGrass P+K produced smaller but still positive effects. Measurements of plant conditions, such as leaf greenness and canopy development, also indicated improved photosynthetic activity in inoculated plots. These results support the role of plant growth-promoting bacteria (PGPB) and arbuscular mycorrhizal fungi in nutrient mobilization, root stimulation, and stress resilience. Although most evidence comes from crops, this study provides novel field-based confirmation of multi-functional microbial inoculant efficacy in turfgrass under this study’s conditions. Full article

Climate change has intensified the occurrence of biotic and abiotic stresses, representing a major threat to agricultural productivity. This climate variability, coupled with the excessive use of agrochemicals, not only compromises environmental sustainability but also exacerbates food insecurity, directly affecting food availability and quality. In this context, biotechnological strategies have proven essential for mitigating the effects of stress on plants, promoting practices focused on agricultural sustainability. Notable among these strategies is the use of plant growth-promoting microorganisms, which are emerging as promising alternatives capable of improving plant tolerance to stress conditions and simultaneously reducing dependence on agrochemicals. These microorganisms can act as nitrogen fixers and solubilizers of nutrients, such as phosphorus and potassium. Additionally, they can influence plant immune responses by inducing systemic resistance and promoting the synthesis of phytohormones, such as auxins, cytokinins, and abscisic acid, which support plant development during the stress response. The interaction between plants and microorganisms represents a sustainable agricultural management strategy capable of enhancing crop tolerance to environmental adversities. In this review, we discuss the microorganisms known to establish beneficial interactions with plants, leading to improved performance under biotic and abiotic stress. Overall, this work highlights the potential of plant–microbe partnerships as a cornerstone for advancing sustainable agriculture in the face of global challenges. Full article

Plants are sessile organisms and are constantly subjected to varying environmental stressors. However, they can mitigate the effects of these stresses by deploying plant growth-promoting (PGP) microbes for their protection. PGP microbes can boost plant growth and enhance plant protection from biotic and abiotic stresses through a wide variety of mechanisms. PGP mechanisms such as biological fixation of nitrogen in soil and plant roots, phosphate solubilization, siderophore production, ACC (1-aminocyclopropane-1-carboxylic acid) deaminase enzyme activity, and production of plant hormones to promote nutrient acquisition and mitigate stresses. Therefore, this review aims to document studies that reported on the role of PGP microbes in plant growth and development and how PGP traits mentioned above and a novel trait flavins (FLs) secretion help plants against biotic and abiotic stress. Several important PGP functions, and the bacterial strains involved in these functions, that can potentially improve plant growth, development, and plant health are reviewed. This review will help to identify gaps for future studies and guide the development of an alternative strategy to use PGP microbes as biofertilizers and biocontrol agents to support eco-friendly agriculture by reducing the indiscriminate use of synthetic agrochemicals. Full article

The transformation pathways of organic carbon (OC) fractions and their interrelationship with microbial activity during natural composting (NC) and vermicomposting (VC) remain poorly understood across pig manure (PM)/straw pellets (SP) ratios. Therefore, the objective of this study was to elucidate the regulatory mechanisms of substrate mixing ratios on carbon fraction transformation and microbial functional networks during these processes. To achieve this, five PM/SP ratios [100:0 (T1), 75:25 (T2), 50:50 (T3), 25:75 (T4), and 0:100 (T5)] were composted with or without earthworms, revealing the T2 (75:25) ratio had most efficient composting performance within 60 days due to the suitable initial C/N ratio (31.65 ± 0.99). Consequently, the T2 treatment reached the highest organic degradation, including TOC reduction (58.6%), TN accumulation (63.9%), and C/N decline (74.8%) in the VC. Vermicomposting markedly stimulated functional microbial groups—nitrogen-fixing, phosphate-solubilizing, and potassium-solubilizing bacteria—thereby enhancing nutrient (N, P, K) bioavailability. The prominence of the optimal C/N ratio across multiple hydrolytic and oxidative enzymes in the VC-T2 further proved that this ratio provided an optimal nutrient and structural balance for both earthworms and microbial consortia. Strong correlations between bacterial abundance and enzyme activities (r ≥ 0.98), lignin and dissolved OC (r ≈ −0.81), and particulate organic carbon and mineral-associated carbon (r > 0.9) highlighted microbially mediated carbon stabilization through enzymatic mineralization, aggregation, and redistribution of carbon from active pools toward mineral-associated OC. This work identifies the critical PM-SP ratio for waste valorization and mechanistically links earthworm–bacteria interactions to carbon sequestration pathways. Full article

The rapid expansion of greenhouse agriculture demands sustainable strategies to maintain soil health and productivity from the outset. Priestia megaterium, a plant growth-promoting rhizobacterium (PGPR), has shown promise in improving plant growth and soil nutrient availability, but its efficacy in newly established greenhouse systems, where the soil microbiome is still developing, remains underexplored. This study evaluated the impact of P. megaterium inoculation on cucumber growth, soil nutrient bioavailability, and soil microbial communities in a greenhouse with only two years of operation. A two-year experiment was conducted with conventional fertilization as the control and P. megaterium inoculation (7.0 × 10⁸ cfu mL⁻¹) at different rates (37.5, 75, 150, and 300 L ha⁻¹) and timings. Soil and plant nutrient content were measured, and microbial communities were analyzed through 16S rRNA sequencing and co-occurrence network analysis. Results showed that applying P. megaterium at 75 L ha⁻¹ during seedling transplantation significantly increased soil available phosphorus (AP) by 11.64–26.48% and available potassium (AK) by 11.27–47.31% compared to the control, while enhancing cucumber yield by 6.71–9.28%. The inoculant also increased soil bacterial diversity, enriched beneficial genera such as Lysobacter, Pseudomonas, and Flavobacterium, and reduced the abundance of Xanthomonas. Furthermore, P. megaterium application promoted a more complex and stable bacterial network, with higher connectivity and modularity. These findings suggest that P. megaterium is a viable strategy for enhancing soil health and productivity in newly established greenhouse systems, offering an environmentally sustainable alternative to traditional fertilization methods. Full article

Fe-oxyhydroxides can incorporate toxic metals during the formation of mineral phases in soils and sediments, thereby potentially altering the environmental reactivity of metals and impacting the microbial communities. In this study, isothermal microcalorimetry has been used to monitor the metabolic activity of Pseudomonas putida KT2440 exposed to pure ferrihydrite and to Pb-, Cd-, and As-bearing ferrihydrites under oxygen-limited conditions. Calorimetric measurements of the integral heat released during the exponential growth were combined with the analysis of dissolved iron and heavy metals, as well as the glucose uptake, to understand how heavy metal incorporation modifies mineral reactivity and microbial heat output. Pure ferrihydrite decreased the integral heat by about 45%, primarily due to glucose and phosphate depletion, Fe(III) leaching, and mineral–cell aggregation. Heavy metal dopants were found to modulate nutrient availability, surface charge, and Fe solubilization, which, in turn, influenced the integral heat. Pb-Fh generated the highest ferrihydrite dissolution and metabolic heat, with a maximum effect at intermediate substitution levels. As-Fh induced moderate Fe release and metabolic activity, consistent with the enhanced phosphate sorption and lowered surface charge. Cd-bearing Fh showed minimal reactivity and yielded the lowest heat output. Microcalorimetry was proven useful for unraveling microbe–mineral interactions in complex contaminated environments. Full article