Search Results (212)

Soil salinization poses a significant constraint to agricultural productivity. However, certain plant growth-promoting bacteria (PGPB) can mitigate salinity stress and enhance crop performance. In this study, a bacterial isolate, R-18, isolated from saline-alkali soil in Ningxia, China, was identified as Enterobacter bugandensis based on 16S rRNA gene sequencing. The isolate was characterized for its morphological, biochemical, and plant growth-promoting traits and was evaluated for its potential to alleviate NaCl-induced stress in maize (Zea mays L.) under hydroponic conditions. Isolate R-18 exhibited halotolerance, surviving at NaCl concentrations ranging from 2.0% to 10.0%, and alkaliphilic adaptation, growing at pH 8.0–11.0. Biochemical assays confirmed it as a Gram-negative bacterium, displaying positive reactions in the Voges–Proskauer (V–P) tests, catalase activity, citrate utilization, fluorescent pigment production, starch hydrolysis, gelatin liquefaction, and ammonia production, while testing negative for the methyl red and cellulose hydrolysis. Notably, isolate R-18 demonstrated multiple plant growth-promoting attributes, including nitrogen fixation, phosphate and potassium solubilization, ACC deaminase activity, and indole-3-acetic acid (IAA) biosynthesis. Under 100 mM NaCl stress, inoculation with isolate R-18 significantly enhanced maize growth, increasing plant height, stem dry weight, root fresh weight, and root dry weight by 20.64%, 47.06%, 34.52%, and 31.25%, respectively. Furthermore, isolate R-18 improved ion homeostasis by elevating the K⁺/Na⁺ ratio in maize tissues. Physiological analyses revealed increased chlorophyll and proline content, alongside reduced malondialdehyde (MDA) levels, indicating mitigated oxidative damage. Antioxidant enzyme activity was modulated, with decreased superoxide dismutase (SOD) and peroxidase (POD) activities but increased catalase (CAT) activity. These findings demonstrated that Enterobacter bugandensis R-18 effectively alleviated NaCl-induced growth inhibition in maize by enhancing osmotic adjustment, reducing oxidative stress, and improving ion balance. Full article

This study analyzed the heavy metal tolerance and chromium reduction and the potential of plant growth to promote Rhizobium sp. OS-1. By genetic makeup, the Rhizobium strain is nitrogen-fixing and phosphate-solubilizing in metal-contaminated agricultural soil. Among the Rhizobium group, bacterial strain OS-1 showed a significant tolerance to heavy metals, particularly chromium (900 µg/mL), zinc (700 µg/mL), and copper. In the initial investigation, the bacteria strains were morphologically short-rod, Gram-negative, appeared as light pink colonies on media plates, and were biochemically positive for catalase reaction and the ability to ferment glucose, sucrose, and mannitol. Further, bacterial genomic DNA was isolated and amplified with the 16SrRNA gene and sequencing; the obtained 16S rRNA sequence achieved accession no. HE663761.1 from the NCBI GenBank, and it was confirmed that the strain belongs to the Rhizobium genus by phylogenetic analysis. The strain’s performance was best for high hexavalent chromium [Cr(VI)] reduction at 7–8 pH and a temperature of 30 °C, resulting in a total decrease in 96 h. Additionally, the adsorption isotherm Freundlich and Langmuir models fit best for this study, revealing a large biosorption capacity, with Cr(VI) having the highest affinity. Further bacterial chromium reduction was confirmed by an enzymatic test of nitro reductase and chromate reductase activity in bacterial extract. Further, from the metal biosorption study, an Artificial Neural Network (ANN) model was built to assess the metal reduction capability, considering the variables of pH, temperature, incubation duration, and initial metal concentration. The model attained an excellent expected accuracy (R² > 0.90). With these features, this bacterial strain is excellent for bioremediation and use for industrial purposes and agricultural sustainability in metal-contaminated agricultural fields. Full article

Reducing the application of chemical fertilizers and remediating heavy metal pollution in soil are important directions in current agricultural research. Utilizing the plant-growth-promoting and remediation capabilities of bacteria can provide more environmentally friendly assistance to agricultural production. In this study, the Burkholderia alba YIM B08401 strain was isolated and identified from rhizospheric soil, subjected to whole-genome sequencing and analysis, and its Cd²⁺ adsorption efficiency and characteristics were confirmed using multiple experimental methods, including atomic absorption spectrometry (AAS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). The results showed that the genome of strain YIM B08401 has a total length of 7,322,157 bp, a GC content of 66.39%, and predicts 6504 protein-coding sequences. It contains abundant functional genes related to nutrient conversion (phosphate solubilization, sulfur metabolism, zinc solubilization, siderophore production), plant hormone regulation (indole-3-acetic acid secretion, ACC deaminase production), phenolic acid degradation, root colonization, heavy metal tolerance, pathogen antagonism, and the production of antagonistic secondary metabolites. Additionally, strain YIM B08401 can specifically bind to Cd²⁺ through various functional groups on the cell surface, such as C-O-C, P=O, and O-H, enabling biosorption. In conclusion, strain YIM B08401 is an excellent strain with plant-growth-promoting, disease-resistant, and bioremediation capabilities, warranting further development as a biofertilizer for agricultural applications to promote green and sustainable agricultural development. Full article

Despite growing interest in improving soil health on cocoa farms, applied research on the impacts of specific amendments on soil and plant outcomes is lacking. An integrated assessment of the impacts of two different organic amendments (compost and vermicompost) and a microbial biofertilizer on soil physical, chemical, and biological properties, as well as cocoa flowering, fruit set, and yield, was conducted in Guayaquil, Ecuador. Complementary culture-dependent and culture-independent methods were used to assess the impacts of amendments on microbial diversity, community composition, and specific taxa. Compost or vermicompost application affected soil chemical properties, including potassium, phosphorus, and sodium, and had small but significant effects on fungal beta diversity. Biofertilizer application slightly lowered soil pH and altered the total abundance of specific taxonomic groups including Azotobacter sp. and Trichoderma sp., with borderline significant effects on Azospirillum sp., Lactobacillus sp., Pseudomonas sp., calcium-solubilizing bacteria, and phosphorus-solubilizing bacteria. Amplicon sequencing (16S, ITS) identified 15 prokaryotic and 68 fungal taxa whose relative abundance was influenced by organic amendments or biofertilizer. Biofertilizer application increased cherelle formation by 19% and monthly harvestable pod counts by 11% despite no impact on flowering index or annual pod totals. This study highlights the tangible potential of microbiome optimization to simultaneously improve on-farm yield and achieve soil health goals on cocoa farms. Full article

Aims: Soil compaction is one of the main challenges in agriculture, negatively affecting cotton growth (Gossypium hirsutum L.), nutrition, and productivity. This study evaluated the efficacy of plant growth-promoting bacteria (PGPB), Exiguobacterium sibiricum, and Pantoea vagans in mitigating the effects of different soil compaction levels (65%, 75%, 85%, and 95%) on cotton performance. Methods: Parameters such as plant height, stem diameter, number of leaves, shoot dry matter (SDM), and nutrient content in leaves, stems, and roots were assessed. The methodology included variance analysis and mean clustering to identify significant differences among treatments using R software. Results: The results indicated that PGPB inoculation improved plant growth and nutrition even under high compaction levels. Cotton height increased by up to 45% in compacted soils (95%), while stem diameter and SDM also showed significant gains. Foliar nutrient levels of N (37.2 g kg⁻¹), Ca, and Mg remained within the adequate range for cotton cultivation, reflecting the efficiency of PGPB in enhancing nutrient absorption. Under severe compaction, Ca accumulation dropped to 18.2 g kg⁻¹, highlighting the physical constraints imposed on the roots; however, the bacterial action mitigated this impact. Additionally, bacterial strains increased the availability of N and P in the soil due to their ability to fix nitrogen, solubilize phosphates, and produce exopolysaccharides that improve soil structure. Conclusions: In conclusion, inoculation with Exiguobacterium sibiricum and Pantoea vagans is an effective strategy to mitigate the impacts of soil compaction on cotton. These bacteria promote plant growth and nutrition and enhance the soil’s physical and biological properties. Full article

Egypt’s rapid population increase has resulted in higher water demand. It may significantly reduce the amount of water available for agriculture, increasing the chance of using saline water in agriculture. Using saline water certainly poses a major threat to maize growth and may severely affect the growth and productivity of this important crop. Therefore, the aim of this study was to isolate newly native salt-tolerant bacteria from Egyptian saline soils and assess their ability to produce growth-promoting substances under salinity stress, as well as test the mitigating impact of these isolated salt-tolerant bacteria along with arbuscular mycorrhizal fungi (AMF) in maize plants under salinity stress. We isolated ninety-seven salt-tolerant bacterial isolates, and these isolates show a high ability to grow under different concentrations of NaCl. The nine most efficient isolates show a high ability to produce indole acetic acid (IAA), gibberellic acid (GA), P-solubilized exopolysaccharides (EPS), proline, and antioxidants under different NaCl concentrations. Using the 16S rRNA gene, the most effective isolate STB 89 was identified, and its impact, along with AMF, on the growth of salinity-stressed maize was tested in a pot experiment. Our results showed that the growth parameters (shoot length, root length, dry weight, and leaf area), photosynthetic-related pigments (Chlorophyll a, b, and carotenoids), NPK content, and antioxidant enzymes (PPO, POX, and CAT) were improved significantly at p ≤ 0.05 due to the bioinoculant applications, while reduced proline accumulation, Na uptake, and the Na⁺/K⁺ ratio in maize plant tissues were observed compared to the control plants. Moreover, the indices of AMF colonization in maize roots and the count of bacteria in the rhizosphere were enhanced due to the bioinoculant applications under salinity stress. In addition, we found that the combined application was more pronounced than the individual application impact. Hence, our results recommended that salt-tolerant bacteria (STB 89) could support salinity, mitigating the impact of AMF in maize plants, as well as allowing better practical techniques for maize cultivation and soil sustainability under salinity stress. Full article

The co-application of biochar, plant growth-promoting rhizobacteria (PGPR), and phosphorus- and potassium-bearing minerals has emerged as a promising strategy for improving soil nutrient availability. However, the synergistic effects and impact factors that facilitate this optimization are yet to be fully elucidated. To address this knowledge gap, we conducted a pot experiment to evaluate the effects of these amendments on tea yield and phosphorus (P)/potassium (K) availability, while employing Random Forest (RF) and Partial Least Squares Structural Equation Modeling (PLS-SEM) to reveal the underlying mechanisms driving these improvements. The results demonstrated that the tripartite combination significantly enhanced tea yield, leaf P/K concentrations, and soil available P (AP)/available K (AK) levels compared to individual applications or pairwise combinations. Analytical modeling identified Chloroflexi bacteria containing pqqc functional genes as key drivers of AP enhancement. The AP was further modulated by β-glucosidase activity, NaHCO₃-P, and AK levels. Critical determinants of AK dynamics included phosphorus-solubilizing bacterial populations, catalase activity, and fundamental soil chemical properties. In summary, our research conclusively shows that the co-application of phosphorus- and potassium-bearing minerals, PGPR, and biochar represents an effective approach to enhancing P and K accessibility in soil, thereby offering a viable alternative to conventional P and K fertilizers in tea cultivation. Full article

The objective of this research was to determine the effect of phosphate-solubilizing bacteria (PSB) on phosphorus availability in agricultural soils and the growth of wheat (Triticum aestivum L.). This applied research considered PSB and phosphorus availability in the soil as variables. An experimental design was employed, comprising four groups of pots containing 1 kg of wheat-cultivated soil (no inoculum, 5% inoculum, 10% inoculum, and 15% inoculum), with three replicates each, using a bacterial suspension of 3 × 10⁸ CFU/mL. Wheat seedling development parameters were evaluated on days 29 and 45, and soil phosphorus availability was assessed on day 45. The 10% inoculum treatment yielded superior results in seedling development: plant height, aerial dry biomass, and root dry biomass showed highly significant differences (p < 0.0001). A 10% PSB dose improved soil phosphorus availability from 72.77 ± 0.13 ppm to 96.68 ± 0.58 ppm compared to the control. These findings highlight PSB as a sustainable alternative for enhancing agricultural productivity, thereby reducing dependence on chemical fertilizers. Full article

This study aimed to evaluate the synergistic effects of zinc sulfate and Pseudomonas spp. in terms of mitigating drought stress in maize (Zea mays L.) by analyzing physiological, biochemical, and morphological responses under field conditions. A two-year (2018–2019) field experiment investigated two irrigation levels (optimal and moderate stress) and twelve treatment combinations of zinc sulfate application methods (without fertilizer, soil, foliar, and seed priming) with zinc-solubilizing bacteria (no bacteria, Pseudomonas fluorescens, and Pseudomonas aeruginosa). Drought stress significantly reduced chlorophyll content, increased oxidative damage, and impaired membrane stability, leading to a 42.4% increase in electrolyte leakage and a 10.9% reduction in leaf area index. However, the combined application of zinc sulfate and P. fluorescens, and P. aeruginosa mitigated these effects, with seed priming showing the most significant improvements. Specifically, seed priming with zinc sulfate and P. fluorescens increased catalase activity by 76% under non-stress conditions and 24% under drought stress. Principal component analysis revealed that treatments combining zinc sulfate and P. fluorescens, and P. aeruginosa were strongly associated with improved chlorophyll content, carotenoid content, and grain yield while also enhancing osmotic adjustment and antioxidant enzyme activity. These findings highlight the potential of the use of zinc sulfate and P. fluorescens as well as P. aeruginosa as sustainable strategies for enhancing maize drought tolerance, mainly through seed priming and soil application methods. Full article

3,4-dimethylpyrazole (DMPZ), when used as a nitrification inhibitor, exhibits volatility, poor thermal stability, high production costs, and limited functionality restricted to nitrogen fixation. To address these limitations and introduce novel phosphorus-solubilizing and soil-loosening abilities, herein, a poly (acrylamide-co-acrylic acid)-encapsulated NI (P(AA-co-AM)-e-NI) is synthesized by incorporating linear P(AM-co-AA) macromolecular structures into NI systems. The P(AA-co-AM)-e-NI demonstrates an obvious phase transition from a glassy state to a rubbery state, with a glass transition temperature of ~150 °C. Only 5 wt% of the weight loss occurs at 220 °C, meeting the temperature requirements of the high-tower melt granulation process (≥165 °C). The DMPZ content in P(AA-co-AM)-e-NI is 1.067 wt%, representing a 120% increase compared to our previous products (0.484 wt%). P(AA-co-AM)-e-NI can effectively reduce the abundance of ammonia-oxidizing bacteria and prolong the duration during which nitrogen fertilizers exist in the form of ammonium nitrogen. It can also cooperatively enhance the conversion of insoluble phosphorus into soluble phosphorus in the presence of ammonium nitrogen (NH₄⁺-N). In addition, upon adding P(AA-co-AM)-e-NI into soils, soil bulk density and hardness decrease by 9.2% and 10.5%, respectively, and soil permeability increases by 10.5%, showing that it has a good soil-loosening ability and capacity to regulate the soil environment. Full article

The utilization rate of phosphorus fertilizer is low in Xinjiang, China, due to the fact that phosphorus is easily fixed by the widely distributed lime soil, leading to the limited contribution of phosphorus fertilizer to crop yield and a decline in crop quality. Phosphate-soluble bacteria can convert insoluble phosphates in the soil into soluble phosphates, playing an important role in soil phosphorus circulation and plant growth. In this study, two bacteria with strong phosphate-solubilizing ability, Enterobacter hormaechei (P1) and Bacillus atrophaeus (P2), were selected from severely salinized soils in Xinjiang, China. The taxonomic status of the strains was determined by analyzing the colony morphology and 16S rRNA gene sequence similarity. Then, the content of organic acids and the activity of acid phosphatase and phytase in the P1 and P2 fermentation broths were measured. Finally, field experiments were conducted in 20 April–2 October 2023 in Wulanwusu, Xinjiang, China, to analyze the effects of phosphate-solubilizing bacterial agents (P1, P2, and P3 (P1 + P2)) on soil physicochemical properties, microbial diversity, and cotton yield. The results showed that both P1 and P2 could significantly solubilize phosphates and produce indole-3-acetic acid (IAA), lactic acid, and tartaric acid. In the cotton field under phosphorus fertilization, the cotton yield of P1, P2, and P3 treatments increased by 10.77%, 8.48%, and 14.00%, respectively, compared with no bacterial agent treatment (CK) (p < 0.05). In addition, the application of phosphate-solubilizing bacterial agents also significantly increased the content of available nutrients and the abundances of Acidobacteria, Bacteroidetes, Fusarium, Bacteroidetes, and Verrucobacteria in the soil compared with CK. In summary, inoculating with phosphate-solubilizing bacteria could promote cotton growth and yield formation by increasing soil available nutrients and altering soil microbial communities. This study will provide a basis for the efficient utilization of phosphorus resources and sustainable agricultural development. Full article

Soil phosphorus is heavily restricted by soil acidification and salinization. There is a need to determine a biological solution for this issue to replace the overuse of chemical phosphorus fertilizer that aggravates adverse conditions, such as salinity, acidity, and metallic toxicity. Therefore, this study aimed at determining the phosphorus dynamics in terms of the soil, growth, and yield of rice under the supplementation of phosphate (P)-solubilizing purple nonsulfur bacteria (PNSB), Cereibacter sphaeroides ST16 and ST26, in salinized soil collected from An Bien district, Kien Giang province, Vietnam, under greenhouse conditions. The experiment followed a completely randomized block design with two factors and four replications. In particular, the reduced percentages of P fertilizer (A) were 0%, 25%, 50%, 75%, and 100% P. The supplementations of C. sphaeroides strains (B) were the negative control, ST16, ST26, and a mixture of both ST16 and ST26. The results showed that supplying the C. sphaeroides ST16 and ST26 reduced the insoluble P content by 10.1–10.6% Fe-P, 10.3–12.2% Ca-P, and 12.7–43.1% Al-P and increased available P by 8.33–27.8%, leading to total P uptake in plants increasing by 29.4–56.1%. The C. sphaeroides strains also reduced soil Na⁺. Therefore, supplying the C. sphaeroides strains increased the rice growth and yield components of rice, leading to a greater yield of 26.5–51.0%. Supplying each strain of ST16 and ST26 reduced 50–100% P fertilizer as recommended. Ultimately, inoculation of the bacterial mixture allowed a reduction by 100% P fertilizer percentage as recommended but the yield remained the still. Full article

Plant growth-promoting bacteria (PGPB) are free-living microorganisms that actively reside in the rhizosphere and affect plant growth and development. These bacteria employ their own metabolic system to fix nitrogen, solubilize phosphate, and secrete hormones to directly impact the metabolism of plants. Generating sustainable agricultural production under various environmental stresses requires a detailed understanding of mechanisms that bacteria use to promote plant growth. In the present study, Pseudomonas aeruginosa (MW843625), a PGP soil bacterium with a minimum inhibitory concentration (MIC) of 150 mM against fluoride (F), was isolated from agricultural fields of Chhattisgarh, India, and was assessed for remedial and PGP potential. This study concentrated on biomass accumulation, nutrient absorption, and oxidative stress tolerance in plants involving antioxidative enzymes. By determining MDA accumulation and ROS (O₂•⁻ and H₂O₂) in Oryza sativa L. under F (50 ppm) stress, oxidative stress tolerance was assessed. The results showed that inoculation with P. aeruginosa enhanced the ability of O. sativa L. seedlings to absorb nutrients and increased the amounts of total chlorophyll (Chl), total soluble protein, and biomass. In contrast to plants cultivated under F-stress alone, those inoculated with P. aeruginosa along with F showed considerably reduced concentrations of F in their roots, shoots, and grains. The alleviation of deleterious effects of F-stress on plants owing to P. aeruginosa inoculation has been associated with improved activity/upregulation of antioxidative genes (SOD, CAT, and APX) in comparison to only F-subjected plants, which resulted in lower O₂•⁻, H₂O₂, and MDA content. Additionally, it has also been reflected from our study that P. aeruginosa has the potential to increase the activities of soil enzymes such as urease, phosphatase, dehydrogenase, nitrate reductase, and cellulase. Accordingly, the findings of the conducted study suggest that P. aeruginosa can be exploited not only as an ideal candidate for bioremediation but also for enhancing soil fertility and the promotion of growth and development of O. sativa L. under F contamination. Full article

Climate change significantly impacts plant growth by reducing the availability of essential nutrients, including phosphorus (P). As an alternative to chemical fertilizers, climate-smart agriculture should prioritize the use of beneficial microorganisms such as P-solubilizing bacteria (PSB). Here, we report the ability of the P1.5S strain of Bacillus safensis to solubilize P under the stress caused by different pH, temperature, and salinity. Genomic data and the TBLASTN algorithm were used to identify genes involved in stress tolerance and P solubilization. Stress tolerance was confirmed by cultivation under varying conditions, while the mechanism of P solubilization was investigated using HPLC. Bioinformatic analysis revealed at least 99 genes related to stress tolerance, 32 genes responsible for organic acids synthesis, as well as 10 genes involved in phosphatase production. B. safensis P1.5S can grow at 37 °C, high NaCl concentrations (15 g/L), and is tolerant of alkaline and acidic conditions. The P1.5S strain primarily solubilizes P by releasing organic acids, including lactic, acetic, and succinic acid. Our data revealed that the efficacy of P solubilization was not affected by abiotic stressors (19.54 µg P/mL). By evaluating the P solubilization ability of B. safensis P1.5S induced by stressors represented by varying pH, temperature, and salinity conditions, this work introduces a new avenue for increasing P availability, which enables and endorses the future development of practical applications of B. safensis P1.5S in challenging agricultural environments. Full article

Soil salinization significantly exacerbates the deficiency in plant-available phosphorus in the soil, thereby adversely affecting plant growth and development. Through various processes, phosphate-solubilizing bacteria in the rhizosphere significantly increase soil-soluble phosphorus content, boosting plant development and stress resistance. This study focused on annual R. soongorica seedlings to examine how rhizosphere phosphate-solubilizing bacteria enhance growth under NaCl-induced stress conditions. This study isolated and characterized rhizosphere phosphate-solubilizing bacteria, evaluating their phosphate solubilization capacity and effects on R. soongorica seedling growth and physiology under NaCl stress through pot experiments, with potential applications in saline soil improvement and desert ecosystem restoration. This study used four treatment groups (control group, NaCl treatment group, bacterial inoculation treatment group, and bacterial and NaCl mixed-treatment group) with twelve treatments and four replicates per treatment. The experimental results demonstrated that five phosphate-solubilizing bacterial strains exhibited a significant phosphate solubilization capacity, accompanied by a notable reduction in pH within the inorganic phosphorus medium. Compared to the NaCl treatment, the net growth of the plant height of R. soongorica seedlings inoculated with strains J23, J24, and M1 under NaCl stress increased significantly (p < 0.05), and all of them more than doubled, and the net growth of the stem diameter of R. soongorica seedlings inoculated with strain J24 increased significantly by 144.17%. The physiological characteristics of R. soongorica seedlings demonstrated significant alterations following inoculation with the five phosphate-solubilizing bacterial strains. The inoculation of R. soongorica seedlings with the five phosphate-solubilizing bacterial resulted in a statistically significant increase in both foliar total phosphorus content and available phosphorus levels within the rhizosphere soil (p < 0.05). Additionally, under NaCl stress conditions, R. soongorica seedlings inoculated with the five phosphate-solubilizing bacterial strains exhibited varying degrees of salt tolerance, with the following descending order of effectiveness: J24 > P2 > J23 > P3 > M1. In conclusion, the rhizosphere phosphate-solubilizing bacteria J24 represents a potentially valuable microbial resource for saline soil amelioration, demonstrating the most pronounced enhancement in both the growth parameters and salt tolerance of R. soongorica seedlings under 300 mmol·L⁻¹ NaCl stress. Full article