Search Results (57)

Fusarium wilt disease, caused by Fusarium oxysporum f. sp. cucumerinum (FOC), leads to widespread yield losses and quality deterioration in cucumber. Endophytes, as environmentally friendly control agents that enhance pathogen resistance in their host plants, may mitigate these problems. In this study, we isolated 14 endophytic bacteria from invasive Ambrosia artemisiifolia and screened the strain Bacillus subtilis TCX1, which exhibited significant antagonistic activity against FOC (inhibitory rate of 86.0%). TCX1 killed Fusarium oxysporum by being highly likely to produce lipopeptide and producing wall hydrolytic enzymes including protease, cellulase, and β-glucanase, thereby inhibiting mycelial growth and spore germination and causing peroxidation of FOC’s cytoplasmic membrane. In addition to its direct effects, TCX1 exerts indirect effects by inducing cucumber resistance to FOC. When cucumber seedlings were inoculated with TCX1, antioxidant enzymes related to disease resistance, including Superoxide dismutase (SOD), Peroxidase (POD), Polyphenol oxidase (PPO) and Phenylalanine ammonialyase (PAL) in cucumber, were significantly increased. The marker genes involved in induced systemic resistance and the salicylic acid signaling pathway, such as npr1, pr1a, pr2, pr9, lox1, and ctr1, were also dramatically upregulated, indicating these pathways played an important role in improving cucumber resistance. Notably, TCX1 can also promote cucumber growth through producing indole-3-acetic acid, solubilizing phosphate, and secreting siderophores. Given that TCX1 has dual functions as both a biological control agent and a biofertilizer, it offers an effective strategy for managing cucumber seedling blight while enhancing plant productivity. Full article

This study aims to identify and evaluate the phosphate-solubilizing ability of endophytic bacteria isolated from roots of Chinese Cymbidium and to assess their impact on phosphorus uptake and plant growth. Thirty strains of endophytic bacteria were isolated from six orchid varieties. Molecular identification based on 16S rRNA gene sequencing revealed that the most frequently isolated strains belonged to the genera Pseudomonas and Burkholderia. Among them, 10 bacterial strains exhibited the capacity to solubilize inorganic and organic phosphorus. Two strains, designated X1 (Paraburkholderia sp. Beta-32) and X13 (Rhizobium freirei PRF81 (X13), were identified as the most effective phosphate-solubilizing bacteria (PSB). Gluconic acid was the dominant organic acid secreted, driving inorganic phosphorus solubilization, while alkaline phosphatase activities facilitated organic phosphorus mineralization. Inoculation with phosphate-solubilizing bacteria (PSB) resulted in increased plant growth and phosphorus content in both leaves and roots as compared to the control plants. PSB treatments also increased available phosphorus content in soil, reduced total phosphorus content, and increased exopolysaccharide and alkaline phosphatase activities. Real-time q-PCR analysis showed that PSB inoculation significantly upregulated the expression of phosphorus transport-related genes, including PDR2, PHF1, PHR1, PHT1;9, and PHT4;4, thereby enhancing phosphorus absorption. Moreover, strains X1 and X13 not only exhibited strong phosphate-solubilizing capacity but also demonstrated stable colonization in both roots and root rhizosphere soil of orchids over extended periods. In conclusion, the endophytic PSB identified with phosphate-solubilizing abilities increased phosphorus availability and its uptake in Chinese Cymbidium, thereby promoting plant growth and development. This is the first attempt to characterize endophytic PSB from roots of Chinese Cymbidium orchids. These findings provide a basis for selection of PSB that are efficient in P uptake for application in microbial fertilizers for orchid cultivation. Full article

Exploring microbial resources from coastal environments is crucial for enhancing food security; however, current knowledge remains limited. This study aimed to isolate and molecularly characterize bacteria associated with maize and groundnut, and to evaluate their potential as plant growth-promoting (PGP) agents. Rhizobacteria were isolated from rhizospheric soil, and endophytic bacteria were obtained from surface-sterilized and macerated plant roots. One gram of each sample was suspended in sterile distilled water in test tubes, serially diluted, and plated on nutrient agar. After incubation, distinct colonies were sub-cultured to obtain pure cultures for biochemical tests, screening for PGP traits, assessment of pH and salt tolerance, optimal growth conditions, bioinoculation potential, and molecular analysis. Out of sixty isolated bacteria, five potent strains, BS1-BS5, were identified. BS3 showed the highest mannanase activity, with a 2.3 cm zone of clearance, while BS2 exhibited high indole-3-acetic acid (IAA) and phosphate solubilization activities of 10.92 µg/mL and 10.78 mg/L. BS1 and BS4 demonstrated high drought tolerance, 0.94 and 0.98 at 10% PEG, with BS1 also showing maximum salt tolerance of 0.76. At 6.0 g and 2.0 g supplementation, BS1 and BS2 utilized 100% lactose and fructose. BS3 exhibited the highest percentage of antifungal activity, with a 30.12% inhibition rate. BS4 and BS5 promoted shoot lengths of 55.00 cm and 49.80 cm, respectively. Although the bacterial species isolated are generally considered pathogenic, their positive effects contributed significantly to maize growth. Full article

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

Microorganisms play a crucial role in agricultural systems. The use of plant growth-promoting bacteria (PGPB) to enhance agricultural production in a sustainable and environmentally friendly manner has been widely recognized as a key technology for the future. In this study, we analyzed the diversity changes of bacteria in different ecological niches of mulberry fields based on culture-dependent methods, and we further evaluated their antibacterial and plant growth-promoting (PGP) activities. A total of 346 cultivable bacteria belonging to 30 genera were isolated from mulberry rhizosphere soil, mulberry plants and silkworm intestines, among which the dominant genera were Bacillus, Pseudomonas, and Enterobacter. The bacterial communities in the mulberry rhizosphere soil were more diverse than those in the mulberry endophytes and in the silkworm intestines. The antibacterial test showed that 30 bacteria exhibited antibacterial activity against the plant pathogen Ralstonia solanacearum. PGP trait assays indicated that 58 bacteria were capable of nitrogen fixation, phosphate solubilization, potassium release and siderophore production simultaneously. The screened functional strains promoted the growth of mulberry saplings. The results of this study highlight new findings on the application of silkworm intestinal bacteria in PGPB. Full article

Understanding the dominant populations and biological functions of endophytic nitrogen-fixing bacteria in apple plants is of great significance for the healthy growth management and sustainable development of apple cultivation. In this study, we investigated the community diversity and potential plant growth-promoting abilities of endophytic nitrogen-fixing bacteria in different tissues of apple trees by combining high-throughput sequencing of the nifH gene with traditional isolation and cultivation techniques. Sequencing results revealed that the endophytic bacteria were affiliated with 10 phyla, 14 classes, 30 orders, 42 families, and 72 genera. Rhizobium was the dominant genus in the roots and twigs, while Desulfovibrio dominated the leaf tissues. The diversity and richness of endophytic bacteria in the roots were significantly higher than those in the leaves. Using four types of nitrogen-free media, a total of 138 presumptive endophytic nitrogen-fixing bacterial strains were isolated from roots, leaves, and twigs. These isolates belonged to 32 taxonomic groups spanning 5 phyla, 8 classes, 11 orders, 13 families, and 18 genera. The nifH gene was successfully amplified from the representative strains of all 32 groups using specific primers. Nitrogenase activity among the isolates ranged from 26.86 to 982.28 nmol/(h·mL). Some strains also exhibited the ability to secrete indole-3-acetic acid (IAA), solubilize phosphate and potassium, and produce siderophores. Six individual strains and three microbial consortia were tested for their plant growth-promoting effects on apple tissue culture seedlings. All treatments showed growth-promoting effects to varying degrees, with the RD01+RC16 consortium showing the most significant results: plant height, number of leaves, and chlorophyll content were 2.4, 3.3, and 4.2 times higher than those of the control, respectively. These findings demonstrate the rich diversity of endophytic nitrogen-fixing bacteria in apple plants and their promising potential for application in promoting host plant growth. Full article

High temperatures pose significant challenges to rice plants’ growth and their associated endophytic bacteria. Understanding how these bacteria respond to heat stress is vital. We assessed the potential of five endophytic bacterial strains derived from Oryza sativa—Bacillus tequilensis LB3, B. coagulans LB6, B. paralicheniformis AS9, B. pumilus LB16, and B. paranthracis i40C—to mitigate heat stress effects on rice plants. These strains demonstrated robust abilities in producing indole-3-acetic acid (IAA) and siderophores, nitrogen fixation, and solubilization of phosphate and potassium. Under high-temperature conditions, they significantly enhanced rice plant growth, with increases in plant length of up to 78% at 40 °C. Notably, LB6 showed the highest biomass increase (195%). The strains also improved chlorophyll SPAD values, an indicator of reduced heat stress effects and improved plant health. Phytohormone profiling and biochemical analyses revealed significant increases in abscisic acid (ABA) levels, reduced lipid peroxidation (MDA), and elevated osmoprotectant proline accumulation under heat stress. Inoculated plants exhibited up to 539 ng g⁻¹ of ABA (vs. 62 ng g⁻¹ in uninoculated controls), a 68% reduction in MDA (indicating less oxidative damage), and enhanced proline synthesis, collectively suggesting improved stress adaptation. These changes were linked to bacterial IAA production and nutrient modulation, which alleviated heat-induced physiological decline. These findings underscore the potential of these endophytes as biofertilizers to improve rice resilience under heat stress. Among the strains, LB6 exhibited superior performance, offering the greatest promise for heat-stress mitigation in rice production. This study advances our understanding of phytohormonal, heat stress signaling, and chemical processes underlying bacterial-mediated thermotolerance, providing a foundation for sustainable agricultural strategies. Future research can explore morphological and biochemical analyses, stress-responsive gene expression (e.g., HSPs, DREBs, and APX) linked to thermotolerance, and the combined effects of selected strains with fertilizers in high-temperature rice cultivation. Full article

Root endophytic microbial communities play a key role in plant health and productivity, yet the extent to which these communities vary across different crop species remains underexplored. This study aimed to investigate the root endophytic bacterial diversity of two important crops—hybrid tomato (Lycopersicon esculentum Mill. var. TNAU CO3) and finger millet (Eleusine coracana L. var. TNAU CO13)—to understand how crop-specific microbiomes contribute to agricultural sustainability and productivity. Targeted 16S rDNA amplicon sequencing was performed on tomato and finger millet root samples. A total of 165,772 and 181,327 16S rRNA gene sequences were generated from tomato and finger millet roots, respectively. These sequences were processed to identify amplicon sequence variants (ASVs), which were then classified taxonomically to assess community composition and functional prediction. Across the two hybrid crops, 1400 ASVs were detected in tomato and 1838 in finger millet. Proteobacteria (52.61–62.09%) were the dominant phylum in both, followed by Actinobacteria, Firmicutes, Bacteroidota, unidentified bacteria, Myxococcota, Verrucomicrobiota, Acidobacteriota, Fusobacteriota, and Chloroflexi. Finger millet roots harbored a more diverse and robust microbial assemblage, particularly enriched with nitrogen-fixing and oxidative stress-mitigating bacteria. In contrast, tomato roots showed a higher abundance of phosphate-solubilizing and biofilm-forming taxa, potentially enhancing resilience to environmental stress. These findings highlight the crop-specific nature of endophytic bacterial communities and their diverse functional capabilities. By revealing distinct microbial profiles in tomato and finger millet, this work provides a valuable foundation for developing strategies to optimize soil health, crop performance, and abiotic stress tolerance. Full article

Muscadine grapes are renowned for their unique traits, natural disease resistance, and rich bioactive compounds. Despite extensive research on their phytochemical properties, microbial communities, particularly endophytic bacteria, remain largely unexplored. These bacteria play crucial roles in plant health, stress tolerance, and ecological interactions. This study represents the first comprehensive effort to isolate, identify, and functionally characterize the bacterial endophytes inhabiting muscadine grape berries using a culture-dependent approach. We isolated diverse bacterial species spanning six genera—Bacillus, Staphylococcus, Paenibacillus, Calidifontibacillus, Curtobacterium, and Tatumella. Microscopic and physiological analysis revealed variations in bacterial morphology, with isolates demonstrating adaptability to varied temperatures. Cluster-based analysis indicated functional specialization among the isolates, with species from Pseudomonadota and Actinomycetota exhibiting superior plant growth-promoting abilities, whereas Bacillota species displayed potential biocontrol and probiotic properties. Among them, Tatumella ptyseos demonstrated exceptional plant growth-promoting traits, including indole-3-acetic acid production, nitrogen fixation, phosphate solubilization, and carbohydrate fermentation. Additionally, Bacillus spp. showed presumptive biocontrol potential, while Paenibacillus cineris emerged as a potential probiotic candidate. The identification of Calidifontibacillus erzurumensis as a novel endophytic species further expands the known biodiversity of grape-associated microbes. These findings provide insights into the metabolic diversity and functional roles of muscadine grape-associated endophytes, highlighting their potential for agricultural and biotechnological applications. Full article

Understanding plant microbe interactions is crucial for achieving sustainable agriculture. This study investigated the effects of inoculating pea plants (Pisum sativum) with two endophytic Bacillus strains, AR11 and AR32, isolated from Artemisia species and characterized by phosphate solubilization, nitrogen fixation, and pathogen antagonism. Utilizing cutting-edge methods such as rarefaction curves, rank abundance modeling, and metagenomic analysis, this research provides a detailed understanding of how these bacterial strains influence plant associated microbiomes. AR11 significantly enhanced microbial diversity, while AR32 showed a moderate effect. Beta diversity analyses revealed distinct shifts in microbial community composition, with AR11-treated samples enriched with beneficial taxa such as Paenibacillus, Flavobacterium, and Methylotenera, known for their roles in nutrient cycling, pathogen suppression, and plant health promotion. This innovative methodological framework surpasses traditional approaches by offering a comprehensive view of ecological and functional microbiome shifts. The study highlights the potential of nonhost bacteria as biostimulants and their role in developing microbiome engineering strategies to enhance plant resilience. These findings contribute to sustainable agriculture by demonstrating how microbial inoculants can be employed to enhance crop productivity and environmental resilience in diverse agricultural systems. Full article

Bacteria associated with plants, whether rhizospheric, epiphytic, or endophytic, play a crucial role in plant productivity and health by promoting growth through complex mechanisms known as plant growth promoters. This study aimed to isolate, characterize, identify, and evaluate the potential of endophytic bacteria from the resurrection plant Selaginella lepidophylla in enhancing plant growth, using Arabidopsis thaliana ecotype Col. 0 as a model system. Plant growth-promotion parameters were assessed on the bacterial isolates; this assessment included the quantification of indole-3-acetic acid, phosphate solubilization, and biological nitrogen fixation, a trehalose quantification, and the siderophore production from 163 endophytic bacteria isolated from S. lepidophylla. The bacterial genera identified included Agrobacterium, Burkholderia, Curtobacterium, Enterobacter, Erwinia, Pantoea, Pseudomonas, and Rhizobium. The plant growth promotion in A. thaliana was evaluated both in Murashige Skoog medium, agar-water, and direct seed inoculation. The results showed that the bacterial isolates enhanced primary root elongation and lateral root and root hair development, and increased the fresh and dry biomass. Notably, three isolates promoted early flowering in A. thaliana. Based on these findings, we propose the S. lepidophylla bacterial isolates as ideal candidates for promoting growth in other agriculturally important plants. Full article

Symbiotic relationships between plants and bacteria play a pivotal role in both natural and agricultural ecosystems, particularly through endophytic colonization or rhizospheric interactions. This study evaluated the plant growth-promoting potential (PGP) of native rhizobial strains Rhizobium sp. ACO-34A and Mesorhizobium sp. 28A (now reclassified within the genus Kumtagia), isolated from Agave americana. Through phenotypic characterization, PGP evaluation, and comparative genomic analysis, both strains demonstrated the ability to thrive under diverse salinity levels and pH conditions, reflecting their adaptability to challenging environments. Rhizobium sp. ACO-34A exhibited superior resistance to antibiotics and heavy metals, coupled with robust PGP traits, such as phosphate solubilization and indole-3-acetic acid (IAA) production, which are crucial for enhancing nutrient availability and root development. Similarly, Mesorhizobium sp. 28A showed exceptional phosphate solubilization efficiency and contributed to improved seedling performance. These findings highlight the capacity of rhizobia associated with agave species to improve plant growth, reduce dependence on chemical fertilizers, and support sustainable agriculture, particularly in nutrient-depleted or semi-arid soils. Genomic analyses revealed the presence of genes linked to stress resilience and nutrient acquisition, underlining the functional versatility of these strains. By leveraging these native rhizobial strains, agricultural practices can achieve higher productivity and sustainability, making them valuable tools for enhancing the agronomic yield and ecological resilience of agave crops for agro-industries. Full article

Endophytic bacteria play crucial roles in plant pathogen protection and growth. Oryza eichingeri is a unique wild rice species rich with genetic resources. Studies have explored beneficial endophytic bacteria and investigated the synergistic interaction between microbes and wild rice. However, the endophytic bacterial community of Oryza eichingeri and their plant growth-promoting (PGP) abilities characteristics remain largely unknown. Here, endophytic bacteria in the root, stem, and leaf tissues of Oryza eichingeri were characterized using metagenomic Illumina 16S rRNA gene sequencing. Additionally, culturable endophytic bacteria were isolated. The metagenomic analysis showed that, compared to those in other tissue compartments, the endophytic bacterial community in the roots had a more complex structure and enhanced functions, and each compartment had its own specific endophytic bacterial biomarkers. A total of 94 endophytic bacteria were isolated from Oryza eichingeri, among which 80 strains possessed PGP traits including increasing phosphate solubilization, siderophore production, IAA production, and nitrogen fixation. These strains displayed good PGP effects on cultivated rice seedlings, promoting the formation of strong root systems, stimulating biomass accumulation, and increasing root length and plant height. These findings provide insights into the composition of the bacterial endosphere of Oryza eichingeri and potential applications of the dominant PGP bacteria in rice cultivation. Full article

Brazil is one of the largest grain producers worldwide, with yields heavily dependent on ecologically and financially expensive inputs. One possible approach to reduce these inputs is inoculation with plant-growth-promoting bacteria, whose large-scale use depends on a continual search for new genotypes for inoculant production. Several bacteria with potential for this have been isolated from plants that are more adapted to stressful environments. Thus, we aimed to evaluate the potential of pangolão grass (Digitaria eriantha cv. Suvernola) endophytic bacteria both in vitro and on maize growth. To this end, endophytic bacteria were isolated from pangolão grass of a tropical semiarid climate and a random subset of 80 strains was evaluated for biological nitrogen fixation, HCN, IAA and siderophore production and calcium phosphate solubilization, and later for maize growth promotion. All strains were positive for at least one of these in vitro growth promotion mechanisms and some strains increased maize plant height and root length, including some with better results than plants receiving commercial inoculants, confirming the potential of endophytic bacteria from stress-adapted plants. In vitro results had poor correlation with plant growth promotion, which indicates that the common practice of using these laboratory techniques as a pre-selection tool before a subset of strains is evaluated for plant growth promotion might result in the rejection of potentially interesting strains. Full article

This study aimed to characterize endophytic bacteria isolated from legume nodules and roots in the rhizosphere soils of Acacia trees in Morocco’s arid regions. The focus was on identifying bacterial strains with plant growth-promoting rhizobacteria (PGPR) traits and antibiotic resistance, which could enhance legume productivity under various abiotic stresses. Autochthonous legumes were used to harbor the endophytic bacteria, including chickpea (Cicer arietinum), faba bean (Vicia faba), lentil (Lens culinaris), and common bean (Phaseolus vulgaris). In a previous study, seventy-two isolates were obtained, and molecular characterization grouped them into twenty-two bacterial isolates. These twenty-two bacterial isolates were then further analyzed for their antibiotic resistance and key PGPR traits, such as phosphate solubilization, indole-3-acetic acid (IAA) production, and siderophore production. The results revealed that 86.36% of the isolates were resistant to erythromycin, 45.45% to ciprofloxacin, 22.73% to ampicillin-sulbactam, and 9.09% to tetracycline, with ciprofloxacin and tetracycline being the most effective. All isolates produced IAA, with HN51 and PN105 exhibiting the highest production at 6 µg of IAA per mg of protein. The other isolates showed varying levels of IAA production, ranging from moderate to low. Siderophore production, assessed using CAS medium, indicated that the strains PN121, LR142, LNR146, and HR26 exhibited high production, while the rest demonstrated moderate to low capacities. Additionally, 18.2% of the isolates demonstrated phosphate solubilization on YED-P medium, with PR135 and LNR135 being the most efficient, achieving solubilization indices of 2.14 and 2.13 cm, respectively. LR142 and LNR146 showed a moderate solubilization efficiency. Overall, these findings indicate that these isolated endophytic bacteria possess significant potential as biofertilizers, owing to their antibiotic resistance, IAA production, siderophore production, and phosphate solubilization abilities. These characteristics position them as promising candidates for enhancing legume growth under abiotic stress and contributing to sustainable agriculture in arid regions. Full article