Endophytic Bacteria Research Articles

Invisible Allies: The Role of Endophytic Entomopathogenic Microbes in Insect Pest Control

Endophytic entomopathogenic microbes, including both bacteria and fungi, hold significant promise as biocontrol agents in sustainable pest management. While the biocontrol potential of entomopathogens are well-established, their role as mutualistic endophytes within plant tissues offers a relatively new avenue for enhancing pest suppression. The ability of these microbes to colonize plant tissues allows them to serve as internal defense agents against insect pests, while simultaneously promoting plant health and resilience to environmental stressors. Here, we explore the growing body of knowledge surrounding the use of endophytic entomopathogenic bacteria and fungi in pest management. These microbes contribute to pest control through direct effects on insect populations, such as mortality and feeding inhibition, as well as indirect plant-mediated mechanisms that enhance plant defenses. Additionally, endophytic entomopathogens provide a range of benefits to their plant hosts, including growth promotion, nutrient acquisition, and protection against pathogens. Despite the clear advantages of using endophytic entomopathogens, there remain key challenges to their widespread implementation. Environmental factors can influence their persistence and efficacy in the field, and their relatively slow mode of action compared to chemical pesticides presents a hurdle for rapid adoption in commercial agriculture. Non-target effects and the development of effective formulations to ensure consistent colonization are also areas that require further investigation. Addressing these challenges through continued research into the complex interactions between endophytes, insects, plants, and their environments will be essential for advancing the integration of endophytic entomopathogenic microbes into sustainable pest management systems.

The impact of pine wilt disease on the endophytic microbial communities structure of Pinus koraiensis

Pine Wilt Disease (PWD) is a devastating pine tree disease characterized by rapid onset, high mortality rate, quick spread, and difficulty in control. Plant microbiome plays a significant role in the development of PWD. However, the endophytic microbial communities of Pinus koraiensis infected by pine wood nematode (PWN) Bursaphelenchus xylophilus remain largely unexplored. In this study, we analyzed the structural changes of endophytic communities of P. koraiensis after infection by the PWN using high-throughput sequencing technology. The results showed that the community structure underwent significant changes as the degree of PWN infection intensified. The diversity and abundance of endophytic fungi in P. koraiensis increased, while those of endophytic bacteria in P. koraiensis decreased during the infection process. Meanwhile, the abundance of some dominant microorganisms has also changed, including species such as Graphilbum and Pseudoalteromonas. Functional prediction analysis showed that the functional composition of endophytic fungi in P. koraiensis was significantly different across the development of PWD, while the composition of endophytic bacteria remained essentially similar. The results indicated that PWN infection had a significant impact on the structure, diversity, abundance, and functional gene composition of endophytic microbial communities in P. koraiensis, and most of the main endophytic microbial groups tended to coordinate with each other. This work provides a better understanding of the changes in endophytic community structure and function caused by PWD infection of P. koraiensis, which may benefit the exploration of potential endophytes for PWN biocontrol.

Endophytic Bacteria Improve Bio- and Phytoremediation of Heavy Metals

Currently, the problem of heavy metal pollution in China is becoming increasingly serious, which poses grave threats to the environment and human health. Owing to the non-biodegradability and toxicity of heavy metals, a more sustainable and ecological approach to remediate heavy metal pollution has always been a focus of attention for environmental researchers. In recent years, many scientists have found that phytoremediation aided by endophytes has high potential to remediate heavy metals owing to its low cost, effectiveness, environmental friendliness, and sustainability compared with physical and chemical methods. Indeed, the mechanism of interaction between endophytes, plants, and heavy metals in the soil is pivotal for plants to tolerate metal toxicity and thrive. In this review, we focus on the mechanism of how endophytic bacteria resist heavy metals, and the direct and indirect mechanisms employed by endophytic bacteria to promote the growth of plants and enhance phytoextraction and phytostabilization. Moreover, we also discuss the application of combinations of endophytic bacteria and plants that have been used to remediate heavy metal pollution. Finally, it is pointed out that although there have been many studies on phytoremediation systems that have been assisted by endophytes, large-scale field trials are important to deliver “real” results to evaluate and improve phytoremediation assisted with microorganisms in polluted natural environments.

Bacillus amyloliquefaciens MZ895491: an endophytic bacterium as potential biocontrol agent in integrated pest management of fall armyworm in maize

ABSTRACT The fall armyworm, Spodoptera frugiperda is a major pest of maize crops and necessitates effective control measures. Excessive use of chemical pesticides often results in the development of resistant insect populations and environmental contamination, highlighting the need for environmentally friendly substitutes. This research aimed to estimate the potential of maize (COH6) apoplastic fluid bacterium Bacillus amyloliquefaciens (MZ895491), as a biocontrol agent against second instar S. frugiperda larvae under laboratory and pot culture conditions. The results suggest that the presence of B. amyloliquefaciens in the artificial diet could reduce the growth and development of S. frugiperda larvae. Metabolic profiling of extracellular components of B. amyloliquefaciens revealed the presence of numerous defensive and anti-feeding metabolites. A study conducted in pots demonstrated that foliar application of B. amyloliquefaciens to 5 d old maize resulted in a significant increase in antioxidant activity (83.3%), chlorophyll content (63.3%) and phenolic content (81.3%) in the leaves of 35 d old maize after 24 h of S. frugiperda infestation. Feeding bioassay further indicated significant reduction in the feeding capacity of S. frugiperda larvae on maize inoculated with B. amyloliquefaciens. The study observed that a metabolic modification in maize leaves likely led to reduced growth in larvae during the whole plant bioassay. This suggests that foliar application of B. amyloliquefaciens may effectively serve as one of the biocontrol agents against Spodoptera frugiperda. The application appears to alter the feeding behaviour of the larvae and modify maize leaf metabolism.

New Occurrence of Nigrospora oryzae Causing Leaf Blight in Ginkgo biloba in China and Biocontrol Screening of Endophytic Bacteria

Ginkgo biloba is a multifunctional composite tree species that has important ornamental, economic, medicinal, and scientific research value. In October 2023, the foliage of G. biloba on the campus of Nanjing Forestry University exhibited leaf blight. Black-brown necrotic spots were observed on a large number of leaves, with a disease incidence of 86%. After isolating a fungus from symptomatic leaves, pathogenicity was tested to satisfy Koch’s postulates. Using morphological features and multi-gene phylogenetic analyses of an internal transcribed spacer (ITS), elongation factor 1-alpha (EF1-α), and beta-tubulin (β-tub), the isolates YKB1-1 and YKB1-2 were identified as Nigrospora oryzae. N. oryzae was previously reported as an endophyte of G. biloba. However, this study shows it to be pathogenic to G. biloba, causing leaf spots. Two endophytic bacteria were isolated from asymptomatic leaves of diseased G. biloba trees, and their molecular identification was performed using 16S ribosomal DNA (16S rDNA). GBB1-2 was identified as Bacillus altitudinis, while GBB1-5 was identified as Bacillus amyloliquefaciens. The screening and verification of endophytic bacteria provide a new strategy for the control of N. oryzae.

Endophytic bacteria in Camellia reticulata pedicels: isolation, screening and analysis of antagonistic activity against nectar yeasts

Camellia reticulata, an ancient plant species endemic to Yunnan Province, China, remains underexplored in terms of its endophytic bacterial communities. The plant tissue pedicel serves as the connection between the flower and the stem, not only delivers nutrients but also transmits metabolic substances from endophytic bacteria to the nectar during long-term microbial colonization and probably improves the antagonistic activity of nectar against yeast. Hence, 138 isolates of endophytic bacteria have been isolated in this study from the pedicels of 12- and 60-year-old C. reticulata. Comparative analysis revealed significantly higher density of endophytic bacteria in older trees. Among these isolates, 29 exhibited inhibitory effects against nectar yeasts. Most of the isolates displayed positive results for Gram staining, catalase reaction, gelatin liquefaction, and motility. Additionally, the isolates demonstrated the ability to utilize diverse substrates, such as glucose, nitrate, and starch. Based on 16S rRNA molecular biology analysis, these isolates were identified to be 11 different species of 6 genera, with the majority belonging to Bacillus genus. Notably, C1 isolate, identified as Bacillus spizizenii, exhibited strongest antagonistic effect against three yeasts, i.e., Metschnikowia reukaufii, Cryptococcus laurentii, and Rhodotorula glutinis, with minimum inhibitory concentration values below 250 μg/mL. Major metabolites of B. spizizenii were aminoglycosides, beta-lactams, and quinolones, which possess antimicrobial activities. Furthermore, KEGG enrichment pathways primarily included the synthesis of plant secondary metabolites, phenylpropanoids, amino acids, alkaloids, flavonoids, neomycin, kanamycin, and gentamicin. Therefore, antagonistic activity of B. spizizenii against yeasts could be attributed to these antibiotics. The findings highlight the diverse endophytic bacteria associated with C. reticulata, indicating their potential as a valuable resource of bioactive metabolites. Additionally, this study provides new insights into the role of endophytic bacteria of pedicels in enhancing nectar resistance against yeasts.

Effect of Bacillus subtilis – based microbiological preparations on the numerical composition of cultured forms of endophytic bacteria, content of mineral nutrition elements, photosynthetic pigments, as well as on chlorophyll fluorescence indices in leaves of columnar apple trees

The results of agrochemical field experiments conducted in an orchard of columnar apple tree (Malus domestica Borkh.) in the Moscow Oblast during the period of 2021–2022 are presented. The research objects were the ‘Valuta’, ‘Triumph’, and ‘President’ varieties. The effect of foliar treatments of plants with Bacillus subtilis (strain V167) and Bacillus subtilis (strain V417) strains, as well as Bacillus subtilis – based microbiological preparations “Extrasol” (strain Ch13) and “Phytosporin-M” (strain 26D) on such indicators as the microbiological and chemical composition of leaves, the content of photosynthetic pigments in leaves, and chlorophyll fluorescence indices was studied. Plant samples were analyzed using standard methodology. When applying strains and microbiological preparations based on Bacillus subtilis, the taxonomic composition of endophytic bacterial forms cultured on dense nutrient media and isolated from leaves was represented by the Bacillus genus. For comparison, when treating plants with Bacillus subtilis strain V417 and “Phytosporin-M”, the Pseudomonas genus was also detected. The number of cultivated forms of endophytic bacteria in the treated plants was consistently growing, having reached the maximum value of 406800 CFU/g in the “Extrasol” variant. Notably, the content of photosynthetic pigments in leaves depended on both the plant variety and the strain used. High values of maximal efficiency of PSII photochemistry (Fv/Fm) were observed both in experimental and control variants. A consistent increase in leaf N content was detected when applying “Extrasol”. In this respect, the ‘President’ variety showed the greatest response, i.e., a 16.1 % increase compared to the control. The ‘President’ and ‘Triumph’ varieties demonstrated an increase in leaf K content under the influence of foliar treatment of plants with the studied strains and microbiological preparations. The greatest effect of 17.2 % above the control was observed in the ‘Triumph’ variety when treated with “Extrasol”. Foliar treatments of ‘President’ and ‘Valuta’ plants with microbiological preparations contributed to increased, compared to the control, Mg contents in their leaves.

Distribution and characterization of endophytic and rhizosphere bacteriome of below-ground tissues in Chinese fir plantation.

None declared.Conflict of interestPlantation of Chinese fir, a popular woody tree species, faces sustainable issues such as nutrient deficiency and increasing disease threat. Rhizosphere and endophytic bacteria play important roles in plant' nutrient absorption and stress alleviation. Our understanding on the microbiome structure and functions are proceeding rapidly in model plants and some crop species. Yet, the spatial distribution and functional patterns of the bacteriome for the woody trees remain largely unexplored. In this study, we collected rhizosphere soil, non-rhizosphere soil, fine root, thick root and primary root samples of Chinese fir, and investigated the structure and distribution of bacteriome, as well as the beneficial effects of endophytic bacterial isolates. We discovered that Burkholderia and Paraburkholderia genera were overwhelmingly enriched in rhizosphere soil and the abundance of Pseudomonas genus was significantly enhanced in fine root. By isolating and testing the nutrient absorption and pathogen antagonism functions of representative endophytic bacteria species in Pseudomonas and Burkholderia, we noticed that P-solubilising functional isolates was enriched in fine root, while pathogen antagonism isolates was enriched in thick root. As a conclusion, our study revealed that the endophytic and rhizosphere environments of Chinese fir hold distinct structure and abundance of bacteriome, with potential specific functional enrichment of some bacterial clades. These findings assist us to further study the potential regulation mechanism of endophytic functional bacteria by the host tree, which will contribute to beneficial microbe application in forestry plantation and sustainable development.

Antibiotics Resistance and PGPR Traits of Endophytic Bacteria Isolated in Arid Region of Morocco

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.

Evaluating Native Bacillus Strains as Potential Biocontrol Agents against Tea Anthracnose Caused by Colletotrichum fructicola

Anthracnose of the tea plant (Camellia sinensis), caused by Colletotrichum spp., poses a significant threat to both the yield and quality of tea production. To address this challenge, researchers have looked to the application of endophytic bacteria as a natural alternative to the use chemical pesticides, offering potential for enhancing disease resistance and abiotic stress tolerance in tea plants. This study focused on identifying effective microbial agents to combat tea anthracnose caused by Colletotrichum fructicola. A total of 38 Bacillus-like strains were isolated from the tea rhizosphere, with 8 isolates showing substantial inhibitory effects against the mycelial growth of C. fructicola, achieving an average inhibition rate of 60.68%. Among these, strain T3 was particularly effective, with a 69.86% inhibition rate. Through morphological, physiological, and biochemical characterization, along with 16S rRNA gene phylogenetics analysis, these strains were identified as B. inaquosorum (T1 and T2), B. tequilensis (T3, T5, T7, T8, and T19), and B. spizizenii (T6). Biological and molecular assays confirmed that these strains could induce the expression of genes associated with antimicrobial compounds like iturin, fengycin, subtilosin, and alkaline protease, which effectively reduced the disease index of tea anthracnose and enhanced tea plant growth. In conclusion, this study demonstrates that B. inaquosorum, B. tequilensis, and B. spizizenii strains are promising biocontrol agents for managing tea anthracnose.

Comparison between bacterial bio-formulations and gibberellic acid effects on Stevia rebaudiana growth and production of steviol glycosides through regulating their encoding genes

Stevia rebaudiana is associated with the production of calorie-free steviol glycosides (SGs) sweetener, receiving worldwide interest as a sugar substitute for people with metabolic disorders. The aim of this investigation is to show the promising role of endophytic bacterial strains isolated from Stevia rebaudiana Egy1 leaves as a biofertilizer integrated with Azospirillum brasilense ATCC 29,145 and gibberellic acid (GA3) to improve another variety of stevia (S. rebaudiana Shou-2) growth, bioactive compound production, expression of SGs involved genes, and stevioside content. Endophytic bacteria isolated from S. rebaudiana Egy1 leaves were molecularly identified and assessed in vitro for plant growth promoting (PGP) traits. Isolated strains Bacillus licheniformis SrAM2, Bacillus paralicheniformis SrAM3 and Bacillus paramycoides SrAM4 with accession numbers MT066091, MW042693 and MT066092, respectively, induced notable variations in the majority of PGP traits production. B. licheniformis SrAM2 revealed the most phytohormones and hydrogen cyanide (HCN) production, while B. paralicheniformis SrAM3 was the most in exopolysaccharides (EPS) and ammonia production 290.96 ± 10.08 mg/l and 88.92 ± 2.96 mg/ml, respectively. Treated plants significantly increased in performance, and the dual treatment T7 (B. paramycoides SrAM4 + A. brasilense) exhibited the highest improvement in shoot and root length by 200% and 146.7%, respectively. On the other hand, T11 (Bacillus cereus SrAM1 + B. licheniformis SrAM2 + B. paralicheniformis SrAM3 + B. paramycoides SrAM4 + A. brasilense + GA3) showed the most elevation in number of leaves, total soluble sugars (TSS), and up-regulation in the expression of the four genes ent-KO, UGT85C2, UGT74G1 and UGT76G1 at 2.7, 3.3, 3.4 and 3.7, respectively. In High-Performance Liquid Chromatography (HPLC) analysis, stevioside content showed a progressive increase in all tested samples but the maximum was exhibited by dual and co-inoculations at 264.37% and 289.05%, respectively. It has been concluded that the PGP endophytes associated with S. rebaudiana leaves improved growth and SGs production, implying the usability of these strains as prospective tools to improve important crop production individually or in consortium.

Exploring the Potential of Bacterial Endophytes in Plant Disease Management.

Endophytic bacteria live in the internal tissues of plants, forming symbiotic, mutualistic, commensalistic and trophobiotic relationships. Some are spread via seeds after sprouting from the rhizosphere or phyllosphere. These bacteria capable of promoting plant growth and impart biotic stress by synthesing plant growth hormones, ACC deaminase, organic acids and siderophore. Endophytes aid in phytoremediation by removing soil contaminants and boosting soil fertility via phosphate solubilization and nitrogen fixation. The endophytic microbes are becoming increasingly popular in biotechnological applications which supports sustainable growth of non-food crops for biomass and biofuel. They offer valuable natural materials which is used in medicine, agriculture and industry. Bacterial endophytes are endowed with the enormous potential in the biological treatment of plant pathogens and considered as the superior alternative to synthetic fungicides. The review emphasizes benefits of bacterial endophytes in promoting plant growth and prospects of agricultural applications viz., increasing crop yield under biotic stress condition and their mode of action towards plant diseases. It also summarises the diverse and vital role of endophytes in agroecosystems as well as insights for sustainable agriculture and crop resilience.

Maize Endophytic Plant Growth-Promoting Bacteria Peribacillus simplex Can Alleviate Plant Saline and Alkaline Stress.

Soil salinization is currently one of the main abiotic stresses that restrict plant growth. Plant endophytic bacteria can alleviate abiotic stress. The aim of the current study was to isolate, characterize, and assess the plant growth-promoting and saline and alkaline stress-alleviating traits of Peribacillus simplex M1 (P. simplex M1) isolates from maize. One endophytic bacterial isolate, named P. simplex M1, was selected from the roots of maize grown in saline-alkali soil. The P. simplex M1 genome sequence analysis of the bacteria with a length of 5.8 Mbp includes about 700 genes that promote growth and 16 antioxidant activity genes that alleviate saline and alkaline stress. P. simplex M1 can grow below 400 mM NaHCO3 on the LB culture medium; The isolate displayed multiple plant growth-stimulating features, such as nitrogen fixation, produced indole-3-acetic acid (IAA), and siderophore production. This isolate had a positive effect on the resistance to salt of maize in addition to the growth. P. simplex M1 significantly promoted seed germination by enhancing seed vigor in maize whether under normal growth or NaHCO3 stress conditions. The seeds with NaHCO3 treatment exhibited higher reactive oxygen species (ROS) levels than the maize in P. simplex M1 inoculant on maize. P. simplex M1 can colonize the roots of maize. The P. simplex M1 inoculant plant increased chlorophyll in leaves, stimulated root and leaf growth, increased the number of lateral roots and root dry weight, increased the length and width of the blades, and dry weight of the blades. The application of inoculants can significantly reduce the content of malondialdehyde (MDA) and increase the activity of plant antioxidant enzymes (Catalase (CAT), Superoxide Dismutase (SOD), and Peroxidase (POD)), which may thereby improve maize resistance to saline and alkaline stress. Conclusion: P. simplex M1 isolate belongs to plant growth-promoting bacteria by having high nitrogen concentration, indoleacetic acid (IAA), and siderophore, and reducing the content of ROS through the antioxidant system to alleviate salt alkali stress. This study presents the potential application of P. simplex M1 as a biological inoculant to promote plant growth and mitigate the saline and alkaline effects of maize and other crops.

Research on the Mechanism of Root Endophytes of Morus alba L. and Fraxinus mandshurica Rupr., Two Host Plants Growing Inonotus hispidus (Bull.) P. Karst., with Metabarcoding and Metabolomics

Inonotus hispidus (Bull.) P. Karst., is a medicinal fungus, which parasitizes broad-leaved tree such as Morus alba L., Fraxinus mandshurica Rupr., and Ulmus macrocarpa Hance. To elucidate the internal relationship between I. hispidus and its hosts, this study analyzed endophytic bacteria and fungi in the roots of M. alba and F. mandshurica growing I. hispidus using the 16S rDNA and ITS high-throughput sequencing technologies; and conducted widely targeted metabolomics research using UPLC-MS/MS. The results showed that Cyanobacteria and unidentified chloroplasts had the highest relative abundance at the phylum and genus levels, respectively. For endophytic fungi, Ascomycota was dominant at the phylum level, while Pleosporales gen Incertae sedis and Oncopodiella were the dominant genera in the roots of M. alba and F. mandshurica, respectively. Widely targeted metabolomics identified 562 differential metabolites and 46 metabolic pathways. Correlation analysis revealed that Xanthobacteraceae, Pseudorhodoplanes, and Bauldia were potential regulators of phenolic acids and phenylpropanoids biosynthesis. Additionally, the genus Oncopodiella was primarily associated with the enrichment of lipids, amino acids, sugars, phenolic acids, and other compounds. This result provides significant insights into the size of the fruiting body, resource development, and active ingredients of I. hispidus from different tree sources.

A study on the potential of endophytic bacteria to promote plant growth: uses in agriculture and future directions

The escalating demand for chemical-free fertilizers in agriculture stems from the adverse impacts associated with chemical fertilizers on both human and animal health, as well as environmental pollution. To address this concern, plant-based microorganisms emerge as a promising solution for the development of environmentally sustainable biofertilizers. Among these microorganisms, endophytic bacteria, residing within plant tissues without causing harm to the host plant, exhibit exceptional attributes conducive to plant growth promotion. Notably, these bacteria demonstrate the production of phytohormones, ammonia, phosphate solubilization, and nitrogen fixation capabilities. Additionally, endophytic bacteria showcase the synthesis of hydrolytic enzymes, the production of siderophores, and antimicrobial activity against pathogens. Such characteristics contribute significantly to the robust growth and development of host plants, fostering tolerance to environmental stresses. This manuscript aims to comprehensively review the plant growth promotion activities of endophytic bacteria, elucidating their diversity and isolation from various plants. Furthermore, it explores the potential future directions in this burgeoning field of research, envisioning the development of endophytic bacterial strains capable of replacing traditional chemical fertilizers. Future research endeavors hold the promise of uncovering novel and effective endophytic bacterial strains, heralding a sustainable paradigm shift in the realm of agricultural fertilization.

Biocontrol potential of Bacillus velezensis SEC-024A against southern blight of industrial hemp

Agroathelia rolfsii is the causative agent of southern blight of industrial hemp, which is a soil-borne infection resulting in grave economic losses in industrial hemp (Cannabis sativa L.). Chemical pesticides are currently the primary means of controlling this disease, but their use is harmful to human health as well as to the environment. Urgent action is needed to screen eco-friendly biocontrol agents against this pathogen. An endophytic bacterium SEC-024A was isolated from the leaf tissue of industrial hemp and exhibited a significant antagonistic effect on A. rolfsii, with a plate inhibition rate of 80.5 % and a pot control effect of 74.1 %. Through whole genome sequencing, SEC-024A was identified to be Bacillus velezensis. It contained multiple gene clusters involved in secondary metabolite biosynthesis and the genes that promote plant growth, colonization, and pathogen defense. Bacillus velezensis SEC-024A produces volatile organic compounds (VOCs) that serve as its primary fungistatic agents. Nine VOCs produced by SEC-024A were detected through gas chromatography-mass spectrometry. These VOCs were individually tested for their antifungal effects. Four volatiles, namely isobutyric acid, tiglic acid, trans-2-octenal, and 2-decanone, exhibited notable inhibitory effects on A. rolfsii with EC50 values of 0.012, 0.038, 0.009, and 0.046 μL/mL, respectively. Additionally, trans-2-octenal demonstrated broad-spectrum antifungal activity against various soil-borne pathogens. Together, this study suggests that B. velezensis SEC-024A holds promise as a novel microbial agent for improving plant growth and controlling diseases.

Plant Growth Promotion in Solanum lycopersicum through Endophytic bacteria Isolated from Flower of Samanea saman

Plant Growth Promotion in Solanum lycopersicum through Endophytic bacteria Isolated from Flower of Samanea saman

Bacterial seed endophytes promote barley growth and inhibits Fusarium graminearum in vitro

ObjectivesSeeds host microbes that function in plant growth and phytopathogen resistance. The aim of the work was to investigate total bacterial community in malting barley seeds and whether their bacterial seed endophytes have dual functional roles in plant growth-promotion and inhibition of Fusarium graminearum, the causative agent of Fusarium head blight (FHB) in barley. We used culture dependent and culture independent methods.ResultsPhylogenetic classification of seed endophytic bacteria based on sequencing data identified B. subtilis, B. licheniformis and B. pumilis as predominant subgroups. Location driven divergence in bacterial endophytic communities was evident based on a clear separation of the samples from Crookston and other location samples. The bio-primed seeds using one hundred and seventy bacterial isolates showed that 3.5% (6/170) of the bacterial isolates conferred greater than 10% increase in both root length (RL) and shoot length (SL), while 19.4% (33/170) and 26.5% (45/170) showed RL and SL specific growth effects, respectively, relative to controls. Among the six bacterial isolates that increased RL and SL, five (#29, #63, #109, #124 and #126) also significantly inhibit the growth of F. graminearum based on in vitro assays. This study identified novel seed bacterial endophytes that could be further exploited for promoting growth during seedling establishment and as biocontrol for combating the devastating scab disease.

Evaluating the Efficacy of Endophytic Bacteria in Controlling Rice Sheath Blight: In Vitro and In Vivo Studies

Rice production is highly susceptible to various pathogens, including Rhizoctonia solani, Curvularia lunata, and Epicoccum rostratum, which are major threats in Asia. Exploring biological control methods using endophytic bacteria offers promising opportunities to enhance rice resilience against these lethal diseases. Using 16S RNA sequencing, we identified four endophytic isolates of Bacillus spp. from rice roots, stems, and leaves. We evaluated the antagonistic activity of these endophytic bacterial isolates against rice pathogens both in vitro and in vivo. These isolates inhibited the growth of C. lunata by 82%, R. solani by 79%, and E. rostratum by 88% in vitro. The detached leaf assay for sheath blight (ShB) disease severity in strains ranged from 10.4% to 73.3%. In vivo results showed that B. amyloliquefaciens (R-19) exhibited the lowest disease intensity at 7.2% and the highest disease suppression at 78.8%. The fungicide propiconazole at 0.1% treatment showed the lowest disease intensity of 7.7% and the highest disease suppression of 73.4%, compared to the infected control. Besides biocontrol efficacy, endophytic isolates enhance plant growth parameters, including shoot height, root length, fresh and dry weights, number of tillers, and grains per tiller. Plant hormones abscisic acid (ABA) and gibberellic acids (GA3) increased by 35% and 53%, respectively, due to B. subtilis (R-20) and B. amyloliquefaciens (R-19), while flavonoid and indole acetic acid (IAA) concentrations surged by 30%–80%. Similarly, chlorophyll (a, b), carotenoids, antioxidant enzymatic activity, phenolic content, carbohydrates, and proline contents were higher compared to the control. This study provides a foundation for future studies on novel and eco-friendly biocontrol agents. In addition, our study recommends the integration of endophytic bacteria into sustainable agriculture for enhancing rice production and reducing disease impacts.

Molecular characterization and chemical engineering of cholesterol oxidase from endophytic bacteria in some medicinal plants

Molecular characterization and chemical engineering of cholesterol oxidase from endophytic bacteria in some medicinal plants