Search Results (155)

Stipagrostis pennata is an important plant in desert ecosystems. Its seed-endophytic bacteria may play a critical role in plant growth and environmental adaptation processes. This study systematically analyzed the community composition and potential plant growth-promoting (PGP) functions of seed-endophytic bacteria associated with S. pennata. The results showed that while the overall diversity of bacterial communities from different sampling sites was similar, significant differences were observed in specific functional genes and species abundances. Nine endophytic bacterial strains were isolated from the seeds, among which Bacillus altitudinis strain L7 exhibited phosphorus solubilizing capabilities, nitrogen fixing, IAA production, siderophore generation, and multi-hydrolytic enzyme activities. Additionally, the genomic sequencing of L7 revealed the key genes involved in plant growth promotion and environmental adaptation, including Na⁺ efflux systems, K⁺ transport systems, compatible solute synthesis genes, and the gene clusters associated with nitrogen metabolism, IAA synthesis, phosphate solubilization, and siderophore synthesis. Strain L7 exhibits salt and osmotic stress tolerance while promoting plant growth, providing a promising candidate for desert microbial resource utilization and plant biostimulant development. Full article

Ancient tea plantations possess extremely important economic and cultivation value. In China, ancient tea plantations with trees over 100 years old have been preserved. However, the status of soil microorganisms, soil fertility, and soil heavy metal pollution in these ancient tea plantations remains unclear. This study took four Dancong ancient tea plantations in Fenghuang, Chaozhou City, and Guangdong Province as the research objects. Soil samples were collected from the surface layer (0–20 cm) and subsurface layer (20–40 cm) of the ancient tea trees. The rhizosphere soil microbial diversity and soil nutrients were determined. On this basis, the soil fertility was evaluated by referring to the soil environmental quality standards so as to conduct a comprehensive evaluation of the soil in the Dancong ancient tea plantations. This study found that Proteobacteria, Acidobacteriota, Chloroflexi, and Actinobacteria were the dominant bacteria in the rhizosphere soil of the Dancong ancient tree tea plantation. Ascomycota and Mortierellomycota are the dominant fungal phyla. Subgroup_2, AD3, Acidothermus, and Acidibacter were the dominant bacterial genera. Saitozyma, Mortierella, and Fusarium are the dominant fungal genera. The redundancy analysis (RDA) revealed that at the bacterial phylum level, Verrucomicrobia showed positive correlations with alkali-hydrolyzable nitrogen (AN), available potassium (AK), and total nitrogen (TN); Proteobacteria exhibited a positive correlation with available phosphorus (AP); and Gemmatimonadetes was positively correlated with total potassium (TK). At the fungal phylum level, Ascomycota demonstrated a positive correlation with TK. TN, AN, and TK were identified as key physicochemical indicators influencing soil bacterial diversity, while TN, AN, AP, and AK were the key physicochemical indicators affecting soil fungal diversity. This study revealed that the soil of Dancong ancient tea plantations has reached Level I fertility in terms of TN, TP, SOM, and AP. TK and AN show Level I or near-Level I fertility, but AK only meets Level III fertility for tea planting, serving as the main limiting factor for soil fertility quality. Considering the relatively abundant TK content in the tea plantations, potassium-solubilizing bacteria should be prioritized over blind potassium fertilizer application. Meanwhile, it is particularly noteworthy that AN and SOM are at extremely high levels. Sustained excess of AN and SOM may lead to over-proliferation of dominant microorganisms, inhibition of other functional microbial communities, and disruption of ecological balance. Therefore, optimizing nutrient input methods during fertilization is recommended. 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

This study evaluates various strains of soil bacterial for use in the development of new biopreparations. Mesophilic spore-forming bacteria were isolated from cultivated soil and analysed for their enzymatic activity, ability to decompose crop residues, and antagonistic properties towards selected phytopathogens. Notably, this is the first cytotoxicity assessment of soil bacterial metabolites on Spodoptera frugiperda Sf-9 (fall armyworm). Bacillus subtilis, Bacillus licheniformis, Bacillus velezensis, Paenibacillus amylolyticus, and Prestia megaterium demonstrated the highest hydrolytic potential for the degradation of post-harvest residues from maize, winter barley, and triticale. They exhibited antimicrobial activity against at least three of the tested phytopathogens and demonstrated the ability to solubilize phosphorus. Metabolites of B. licheniformis (IC50 = 8.3 mg/mL) and B. subtilis (IC50 = 144.9 mg/mL) were the most cytotoxic against Sf-9. We recommend the use of the tested strains in industrial practice as biocontrol agents, plant growth biostimulants, crop residue decomposition stimulants, and bioinsecticides. Future studies should focus on assessing the efficacy of using these strains under conditions simulating the target use, such as plant microcosms and greenhouses and the impact of these strains on the abundance and biodiversity of native soil microbiota. This research can serve as a model procedure for screening other strains of bacteria for agricultural purposes. Full article

Sweet potato (Ipomoea batatas (L.) Lam.), as an important crop, is rich in polyphenols, vitamins, minerals, and other nutrients in its roots and leaves and is gradually gaining popularity. The use of endophytic bacteria to improve the quality of sweet potato can protect the environment and effectively promote the sustainable development of the sweet potato industry. In this study, 12 strains of endophytic bacteria were isolated from sweet potato. Through nitrogen fixation, phosphorus solubilization, indoleacetic acid production, siderophore production, ACC deaminase production, and carboxymethyl cellulose production, three strains with multiple biological activities were screened out. Among them, MEPW12 had the most plant growth-promoting functions. In addition, MEPW12 promoted host chlorophyll accumulation and inhibited pathogen growth and colonization in sweet potato roots and can utilize various carbon sources and salts for growth. It can also grow in extreme environments of high salt and weak acid. MEPW12 was identified as Bacillus amyloliquefaciens with a genome size of 3,928,046 bp and a GC content of 46.59%. After the annotation of multiple databases, it was found that MEPW12 had multiple enzymatic activities and metabolic potential. Comparative genomics and pan-genomics analyses revealed that other Bacillus sp. strains of MEPW12 have similar functions. However, due to adaptation to different growth environments, there are still genomic differences and changes. Inoculation with MEPW12 induced the high expression of IbGH3.10, IbERF1, and other genes, thereby promoting the growth of sweet potatoes. Bacillus amyloliquefaciens strain MEPW12 is a sweet potato endophyte with multiple growth-promoting functions, which can promote the growth of sweet potato seedlings. This study provides new microbial resources for developing microbial agents and improving the quality of sweet potatoes. Full article

Soil salinization severely impacts plant cultivation. Lilium pumilum (L. pumilum) exhibits tolerance to saline–alkali stresses. One Bacillus cereus strain, LpBc-47, possesses the ability of growth promotion and saline–alkali tolerance. The microbial diversity of L. pumilum was assessed through metagenomic sequencing. LpBC-47 obtained from L. pumilum was subjected to physiological and biochemical analyses and whole-genome sequencing. The effects of endophytic bacteria on plants were evaluated by measuring growth parameters, physiological indices, antioxidant enzyme activities, and ROS content. Microbial diversity analysis revealed that the abundance of endophytic bacteria in L. pumilum decreased under saline–alkali conditions, whereas the abundance of Bacillus cereus increased. Physiological and biochemical analysis showed that LpBC-47 has the characteristics of promoting growth and reducing plant damage caused by salt–alkali stress, such as phosphorus solubilization, nitrogen fixation, siderophore production, IAA, and ACC deaminase synthesis. Genomic analysis revealed that LpBC-47 contains growth-associated and stress-alleviation genes. GFP indicated the colonization of LpBc-47 in the roots and bulbs of L. pumilum. The LpBc-47 inoculant plant increased leaf length and dry weight, elevated proline and chlorophyll levels, enhanced antioxidant enzyme activity, and reduced oxidative damage. This study highlights the potential of LpBc-47 for improving plant growth under saline–alkali conditions. 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

Endophytic bacteria in Sphagnum palustre have a growth-promoting effect on plants. In this study, the endophytic bacterium strain J11 in S. palustre was isolated and identified as Bacillus cereus, and its growth cycle, functional characteristics, and effects on maize growth were analyzed. The results indicate that as B. cereus, the growth cycle of J11 consists of four phases, and the logarithmic phase lasts 2~24 h, with the abilities of phosphorus solubilization, protease, IAA, siderophore, and NH₃ production. The phosphorus solubilization ability of J11 ranges from 1.66 ± 0.07 to 1.98 ± 0.07 mg/L, and the IAA production varies from 1.51 ± 0.07 to 8.67 ± 0.16 mg/L. It has a growth-promoting effect on maize by increasing the seed germination rate by 29.27%, plant height by 4.21%, leaf length by 17.12%, leaf width by 29.51%, above-ground fresh weight by 50.79%, below-ground fresh weight by 46.30%, and chlorophyll content by 56.81%. This study represents the first report on the isolation and identification of B. cereus from S. palustre. Furthermore, this study systematically investigated its multiple plant growth-promoting traits and functional characteristics. These findings provide valuable resources and a theoretical foundation for the development and functional exploration of microbial resources in agricultural applications. 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

Pseudomonas extremaustralis was first isolated from Antarctica and gained interest for its ability to thrive in extreme environmental conditions and degrade recalcitrant compounds. Some strains have been identified as phosphobacteria, which play a significant role in phosphorus (P) cycling by solubilizing or mineralizing insoluble phosphate forms for plant uptake. However, there is limited knowledge about the genomic mechanisms involved in P-cycling in the species P. extremaustralis. In this study, we aimed to evaluate the genomic potential of P. extremautralis as a phosphobacteria species by screening genes related to P-cycling. Two P. extremaustralis strains from pisciculture sludge residues were selected to sequence their complete genomes based on their ability to solubilize inorganic P in vitro, and an in silico analysis with all the P. extremaustralis genomes was performed to identify the presence of phosphorus-cycling-related genes. Genes mainly involved in the metabolic processes of two-component systems and transporters, and genes involved in organic acid production and alkaline phosphatases, were identified. This study helps us to understand the metabolic potential of this species and its role as a solubilizer of phosphates and thus a facilitator of plant-available phosphorus, which could guide the use of this species of phosphobacteria in the development of sustainable agriculture. Full article

Phosphorus is an important macronutrient for plant development, but its bioavailability in soil is often limited. Phosphate-solubilizing microorganisms play a vital role in phosphorus biogeochemistry, offering a sustainable alternative to chemical fertilizers, which pose environmental risks. Manual measurements for quantifying phosphate solubilization capacity are laborious, subjective, and time-consuming, so there is a need to develop more efficient and objective approaches. This study aimed to develop and validate a machine vision system called IGLOO to automate and optimize the determination of relative phosphate solubilization efficiency in phosphate-solubilizing bacteria. IGLOO was developed using YOLOv8 in conjunction with creating and labeling a dataset of images of bacterial colonies grown in vitro with the bacterial strains Enterobacter R11 and FCRK4. The model was trained with a different number of epochs. IGLOO’s performance was evaluated by comparing its segmentation accuracy with accepted metrics in the domain and by contrasting its solubilization efficiency estimates with experts’ manual measurements. The model achieved greater than 90% accuracy for colony and halo detection, with a relative error of less than 6% compared to manual measurements, demonstrating its reliability by minimizing observer variability. Finally, IGLOO represents a significant advance in the quantitative evaluation of phosphate solubilization of microorganisms because it reduces analysis time and provides objective and reproducible results for agricultural studies. 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