Search Results (150)

Plant microbiota contributes to nutrient absorption, and the production of hormones and vitamins, and plays a crucial role in responding to environmental stress. We hypothesized that Vaccinium spp. harbour a unique microbiota that enables them to coexist in extreme environments such as saline, nutrient-poor, and waterlogged conditions. Upon examining Bacillus spp. endophytes isolated from blueberries, cranberries and lingonberries in vitro, we identified B. halotolerans (Bil-LT1_1, Bil-LT1_2) and B. velezensis (Cran-LT1_8, Ling-NOR4_15) strains that inhibit the growth of five pathogenic fungi and five foodborne bacteria. Whole-genome sequencing provided insights into genome organization and plasticity, helping identify mobile elements and genes potentially acquired through horizontal gene transfer. Functional annotation identified genes associated with plant colonization, stress tolerance, biocontrol activity, and plant growth promotion. Comparative genomic analyses revealed key biosynthetic gene clusters (BGCs) responsible for producing antifungal metabolites, including lipopeptides and polyketides. Genes supporting plant nutrition, growth, and environmental adaptation were present also in these strains. Notably, isolated endophytes exhibited particularly high levels of genomic plasticity, likely due to horizontal gene transfer involving gene ontology (GO) pathways related to survival in polymicrobial and foreign environments. Full article

Microorganisms take an active part in the processes of microbiologically influenced corrosion, which is protected against by using bactericides—often toxic compounds—with inhibitory properties. There are many studies of eco-friendly “green” biocides/inhibitors, in particular those based on microbial metabolites. Indicators for the processes of microbial corrosion of steel 3 induced by the sulfate-reducing bacteria Desulfovibrio oryzae NUChC SRB2 under the influence of the strains Bacillus velezensis NUChC C2b and Streptomyces gardneri ChNPU F3 have not been investigated, which was the aim of this study. The agar well diffusion method (to determine the antibacterial properties of the supernatants) was used, along with the crystal violet (to determine the biomass of the biofilm on the steel) and gravimetric methods (to determine the corrosion rate). A moderate adhesiveness to steel 3 was established for D. oryzae due to its biofilm-forming ability. The presence of a supernatant on cultures of S. gardneri, B. velezensis and their mixture (2:1) did not reduce the biofilm-forming properties of D. oryzae. Compared to the control, a decrease in the corrosion rate was recorded for the variant of the mixture of the studied bacterial culture supernatants. This indicates the potential of this mixture for use in corrosion protection in environments with sulfate-reducing bacteria, which requires further research. Full article

The major objective was to investigate the protective capabilities of endophytic bacterial strains isolated from a number of medicinal plant species towards Aspergillus spp. secured from the internal tissues of fungi-infected peanuts. Among 32 fungal isolates surveyed for mycotoxin production in various culture media (PDA, RBCA, YES, CA), 10 isolates qualitatively producing AFB₁, besides 10 OTA-producers, were assayed by HPLC for quantitative toxin production. Aspergillus spp. isolate Be 13 produced an extraordinary quantity of 1859.18 μg mL⁻¹ AFB₁, against the lowest toxin level of 280.40 μg mL⁻¹ produced by the fungus isolate IS 4. The estimated amounts of OTA were considerably lower and fell in the range 0.88–6.00 μg mL⁻¹; isolate Sa 1 was superior, while isolate Be 7 seemed inferior. Based on ITS gene sequencing, the highly toxigenic Aspergillus spp. isolates Be 13 and Sa 1 matched the description of A. novoparasiticus and A. ochraceus, respectively, ochraceus, respectively, which are present in GenBank with identity exceeding 99%. According to 16S rRNA gene sequencing, these antagonists labeled Ar6, Ma27 and So34 showed the typical characteristics of Pseudomonas aeruginosa, Bacillus subtilis and Bacillus velezensis, respectively, with similarity percentages of 99–100. The plant growth-promoting activity measurements of the identified endophytes indicated the production of 16.96–80.00 μg/100 mL culture medium of IAA. Phosphate-solubilizing capacity varied among endophytes from 2.50 to 21.38 μg/100 mL. The polysaccharide production pool of bacterial strains ranged between 2.74 and 6.57 mg mL⁻¹. P. aeruginosa Ar6 and B. velezensis successfully produced HCN, but B. subtilis failed. The in vitro mycotoxin biodegradation potential of tested bacterial endophytes indicated the superiority of B. velezensis in degrading both mycotoxins (AFB₁-OTA) with average percentage of 88.7; B. subtilis ranked thereafter (85.6%). The 30-day old peanut (cv. Giza 6) seedlings grown in gnotobiotic system severely injured due to infection with AFB₁/OTA-producing fungi, an effect expressed in significant reductions in shoot and root growth traits. Simultaneous treatment with the endophytic antagonists greatly diminished the harmful impact of the pathogens; B. velezensis was the pioneer, not P. aeruginosa Ar6. In conclusion, these findings proved that several endophytic bacterial species have the potential as alternative tools to chemical fungicides for protecting agricultural commodities against mycotoxin-producing fungi. Full article

Spore-forming Bacilli have been explored due to their potential biotechnological features and applications in human health and functional food research. This study focuses on the genetic and phenotypical characterization of the functional probiotic properties of Bacillus velezensis P45, a strain isolated from fish intestines. B. velezensis P45 exhibited antimicrobial activity against Gram-positive and Gram-negative pathogens and demonstrated strong autoaggregation and biofilm formation properties in vitro. The strain also showed tolerance to gastrointestinal conditions and ability to metabolize and adhere to mucin. In silico analysis confirmed the absence of virulence factors and antibiotic resistance genes, reinforcing its safety as a probiotic candidate. Genome mining revealed the presence of genes related to adhesion, such as fibronectin-binding protein and enolases, and for the synthesis of secondary metabolites, including the antimicrobial lipopeptides fengycin, surfactin, and bacillibactin. In addition, phylogenetic comparison using the yloA (rqcH) gene associated with gut adhesion clustered strain P45 with other probiotic Bacillus and B. velezensis strains, while separating it from pathogenic bacteria. Thus, the strain B. velezensis P45 could be a valuable candidate as a probiotic due to its functional properties and safety. Full article

Peanut root rot poses a significant threat to global peanut production. In order to identify the new pathogen of peanut root rot in Shandong province, China, and to screen the effective antagonistic biocontrol strains against the identified pathogen, ten symptomatic plants from a peanut field (10% disease incidence) of Rongcheng were sampled for pathogen isolation. The predominant isolate RC-103 was identified as Ceratobasidium sp. AG-A through morphological characterization and phylogenetic analysis of ITS and RPB2 sequences. Pathogenicity was confirmed via Koch’s postulates. Three potent biocontrol strains, namely Bacillus subtilis LY-1, Bacillus velezensis ZHX-7, and Burkholderia cepacia Bc-HN1, were screened for effective antagonism against isolate RC-103 by dual-culture analysis. Their cell suspensions could significantly inhibit the hyphal growth of isolate RC-103, with the percentage inhibition of 54.70%, 45.86%, and 48.62%, respectively. Notably, the percentage inhibition of 10% concentration of the cell-free culture filtrate of B. subtilis LY-1 was as high as 59.01%, and the inhibition rate of volatile organic compounds of B. cepacia Bc-HN1 was 48.62%. Antagonistic mechanisms primarily involved the induction of hyphal abnormalities. In addition, the culture filtrate of these biocontrol bacteria significantly promoted the growth of peanut and increased the resistance of peanut plants to isolate RC-103, with the biocontrol efficiency reaching 41.86%. In summary, this study identified a novel pathogen of peanut root rot, Ceratobasidium sp. AG-A, which was reported for the first time in China, and screened three highly effective antagonistic biocontrol strains against Ceratobasidium sp. AG-A isolate RC-103, providing the scientific basis to study the epidemiology and management of this disease. Full article

Piglet diarrhea caused by weaning stress will increase the mortality rate and seriously affect swine industry production efficiency. Probiotic supplementation has been reported to effectively alleviate weaning diarrhea by inhibiting the colonization of pathogenic microorganisms; however, the underlying mechanisms remain unclear. In this study, we isolated a strain of Bacillus velezensis and conducted a series of in vivo and in vitro experiments to explore its effects on weaned piglets. The piglets were fed for a 28-day period, and the results showed that dietary supplementation of B. velezensis 411 significantly alleviated weaning diarrhea (p = 0.019) and improved the average daily gain (ADG) of piglets throughout the experimental period (p = 0.004). The intestinal antioxidant capacity of piglets was also significantly enhanced. Whole-genome sequencing revealed that B. velezensis 411 contains a protein-encoding circular chromosome, which is involved in biological processes such as sporulation and antibiotic secretion. Supplementation with B. velezensis 411 significantly increased the abundance of Akkermansia in intestine samples and significantly decreased the abundance of pathogenic bacteria, including Escherichia coli and Staphylococcus aureus, in piglets (p < 0.05). The transcriptomic results suggest that B. velezensis 411 supplementation may alter the composition of intestinal microorganisms through regulating the expression of MPEG1. Collectively, dietary B. velezensis can relieve diarrhea in piglets and improve their production performance by influencing the antioxidant capacity of the intestines and the balance of the intestinal flora. This study provides valuable insights into the potential application of Bacillus velezensis in mitigating weaning-associated issues in piglets. Full article

The fungus Alternaria alternata, which causes tobacco brown spot disease, poses a serious threat to the tobacco industry. Beneficial microorganisms and their secondary metabolites have emerged as a promising green strategy for disease management. This study recovered 16 endophytic bacterial strains from Mentha haplocalyx Briq., a therapeutic herb. The study revealed that strain B5, with an inhibition rate of 82.76%, exhibited the highest antifungal activity against A. alternata. This strain exhibited broad-spectrum antifungal activity, with inhibition rates ranging from 66.34% to 87.23%. Phylogenetic analysis of 16S rDNA and gyrA gene sequences identified it as Bacillus velezensis (GenBank: PV168970 and PV173738). Further characterization revealed that strain B5 can secrete cell wall-degrading enzymes, produce IAA, and synthesize siderophores. The growth of mycelium in A. alternata was greatly reduced by both the ethyl acetate extract and the filtered liquid from the sterile fermentation, resulting in marked morphological abnormalities. Multiple antifungal active substances were identified through liquid LC-MS analysis. Greenhouse experiments demonstrated that the B5 fermentation broth effectively suppressed the occurrence of tobacco brown spot disease, achieving a relative control efficacy of 60.66%, comparable to that of 10% difenoconazole water dispersible granule (WDG). Additionally, strain B5 enhances plant disease resistance by activating the activities of key defense enzymes. B. velezensis B5 serves as a safe alternative to chemical fungicides and is highly effective at controlling tobacco brown spot disease. 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

We investigated the effect of probiotic Bacillus velezensis strains (LSSA01, 15AP4 and 2084) on pathogens causing post-weaning diarrhea in piglets (Enterotoxigenic Escherichia coli, Clostridium perfringens, Salmonella spp.). We studied the effect of B. velezensis and its cell-free supernatant on (1) pathogen growth; (2) IPEC-J2 cell cytokine and tight junction protein expression; (3) IPEC-J2 cell ‘wound’ recovery; (4) adhesion to IPEC-J2 cells and pathogen exclusion; and (5) Caenorhabditis elegans survival following pathogen exposure. Cell-free supernatant (CFS) from all strains inhibited the growth of ETEC F4 and F18 (by 36.9–53.2%; p < 0.05). One or more strains inhibited C. perfringens and Salmonella spp. (p < 0.05). Strain 2084 CFS increased IL-8 expression (+12.0% vs. control; p < 0.05; 6 h incubation), whereas LSSA01 CFS increased the expression of tight junction proteins (p < 0.05 vs. control; 6 h incubation) and accelerated 96 h ‘wound’ healing. Colony-forming units (CFUs) of all strains displayed a higher binding affinity to IPEC-J2 cells than 12 ETEC isolates, reduced adhesion of ETEC F4 and F18 and extended C. elegans survival over 30 d. The results indicate that probiotic B. velezensis strains have potential for use in the control of PWD pathogens. Full article

Background/Objectives: Clavulanic acid (CA) is produced by cell suspension cultures of Streptomyces clavuligerus ATCC 27064, and is widely used as a beta-lactamase inhibitor to combat antibiotic resistance. CA titers are moderate due to bioprocess complexity, prompting ongoing efforts to overcome these limitations. Methods: In this study, we aimed to evaluate the effect of live and inactivated Bacillus velezensis FZB42 cells on CA production in S. clavuligerus, and to explore the transcriptional response underlying this interaction using RNA-seq technology. Results: The addition of dead and live cells of B. velezensis improved CA production by 1.4 and 2.0-fold, respectively. Furthermore, the transcriptome of S. clavuligerus, obtained with live cells of B. velezensis FZB42 at the peak of maximum CA production, revealed that 410 genes were up-regulated and 594 were down-regulated under these conditions, with a padj < 0.05. Most of the genes from the cephamycin C and CA clusters were up-regulated, which correlates well with the increase in CA production. Likewise, S. clavuligerus ATCC 27064 enhanced the expression of genes encoding enzymes that scavenge endogenous H₂O₂, as well as other genes related to oxidative stress defense. Regarding downregulated genes, we found that S. clavuligerus decreased the expression of genes involved in the biosynthesis of terpenoids, polyketides, and lantibiotics, as well as the expression of the operon involved in the synthesis of the pyrroloquinoline quinone (PQQ) cofactor. Conclusions: These findings contribute to the understanding of S. clavuligerus metabolism and pave the way for future metabolic engineering efforts aimed at obtaining CA-overproducing strains. Full article

Background/Objectives: The agriculture sector faces significant challenges due to global climate change, environmental stressors, and rapid population growth, compounded by unsustainable farming practices. This study investigates the potential of the endophytic bacterial strain B.B.Sf.2, isolated from the bark of Salvia fruticosa and identified as Bacillus velezensis through phylogenomic analyses. Methods: To address these issues, eco-friendly techniques, such as the application of plant-associated microbes, are gaining attention. Genome mining revealed numerous secondary metabolite biosynthetic gene clusters associated with plant growth promotion, biocontrol, colonization, and defense elicitation. Results: The strain exhibited strong antagonistic activity against phytopathogens, mediated by diffusible and volatile compound production, along with plant-growth-promoting traits and environmental adaptability. Genome mining revealed numerous secondary metabolite biosynthetic gene clusters associated with plant growth promotion, biocontrol, colonization, and defense elicitation. B.B.Sf.2 effectively inhibited Colletotrichum species causing olive anthracnose and suppressed Botrytis cinerea, the gray mold pathogen, in post-harvest studies on infected fruits. Bioautography of ethyl acetate extracts demonstrated bioactivity against B. cinerea, attributed to iturin-like metabolites. The extracts maintained bioactive properties regardless of fungal interaction. Furthermore, the strain significantly promoted the growth of Arabidopsis thaliana via diffusible and volatile compounds. Conclusions: Our results highlight the multifunctional potential of B.B.Sf.2 as a biocontrol and growth-promoting agent, warranting further evaluation in field applications to enhance sustainable agriculture. Full article

Root-knot nematode (RKN) causes severe yield loss in cucumber. Understanding the interactions of biocontrol agent–soil microbiomes and RKNs is essential for enhancing the efficacy of biocontrol agents and nematicides to curb RKN damage to cucumber. The field experiment in this work was conducted to determine the ability of Bacillus velezensis GHt-q6 to colonize cucumber plants, investigate its effect on the control of RKNs, and assess its influence on soil microbiology in the inter-root zone of cucumber plants. After 10 days post-treatment (DPT), GHt-q6-Rif could stably colonize the roots (4.55 × 10⁴ cfu·g⁻¹), stems (3.60 × 10³ cfu·g⁻¹), and leaves (3.60 × 10² cfu·g⁻¹) of cucumber. The high-throughput sequencing results suggested that the bacterial community diversity increased at the late development phase (p > 0.05). The strain GHt-q6 increased the relative abundance of beneficial bacteria (Gemmatimonadaceae, Sphingomonadaceae, Pseudomonadaceae). Throughout the complete cucumber growth period, strain GHt-q6 significantly increased soil urease, sucrase, accessible potassium, and phosphorus (p < 0.05). However, strain GHt-q6 had a minimal effect on catalase activity. At the pulling stage, strain GHt-q6 exhibited 43.35% control effect on cucumber RKNs, which was 7.54% higher than that of Bacillus subtilis. The results highlighted the significant potential of the strain GHt-q6 to manage cucumber RKNs and improve soil microecology. Hence, the applications of B. velezensis GHt-q6 can enhance the nematicidal action to curb RKN infecting cucumber. Full article

Bacillus velezensis is a promising mosquito vector biocontrol agent due to its potent larvicidal properties. This study investigated the lethal and sublethal effects of exposure to crude toxin of B. velezensis strain WHk23 on Culex quinquefasciatus. Toxicity bioassays showed a median lethal concentration of 28.30 µg/mL for third instar larvae. In addition to direct larval mortality, sublethal exposures resulted in concentration-dependent decreases in survival, fecundity, and fertility. Exposure to different concentrations was found to accelerate larval development, resulting in larger females, yet those females exhibited lower lifespan and diminished reproductive success. These results suggest that exposure to B. velezensis not only reduces mosquito populations but also has lasting effects on important life history parameters, ultimately lowering vectorial capacity and disease transmission risk. This study provides valuable insights into the lethal and sublethal consequences of B. velezensis exposure. Given its potent larvicidal properties, B. velezensis represents a promising biocontrol agent for mosquito vectors. Full article

Background: Maize is easily contaminated by Aspergillus flavus, and the aflatoxin produced by A. flavus has been classified as a Group 1 carcinogen, for which there are currently no effective control measures. Biological control is regarded as an environmentally friendly and safe approach. Strains ZH179, ZH409, and ZH99 are three bacteria isolated from our laboratory that exhibit antagonistic effects against A. flavus. We conducted experiments to investigate their biocontrol efficacy. Results: The experimental results demonstrated that these three strains effectively inhibited A. flavus on plates and stored maize seeds. Identification revealed that ZH179 is Bacillus velezensis, while ZH409 and ZH99 are B. amyloliquefaciens. We also identified lipopeptide synthetase-related genes, including srfAA, srfAD, fenA, fenB, ituA, ituB, ituD, bmyA, bmyB, and bmyC, in these three strains. Furthermore, LC-MS analysis confirmed that these strains could produce lipopeptide compounds such as surfactin, fengycin, iturin, and bacillomycin. Using the Oxford cup method, we found that the lipopeptide compounds produced by these strains can inhibit the growth of A. flavus. Conclusion: These findings suggest that strains ZH179, ZH409, and ZH99 have good control effects on A. flavus during the storage of maize, primarily due to the lipopeptide compounds. This study provides a theoretical basis for using these three strains in the biological control of A. flavus. Full article

Monilinia spp., which causes brown rot, is one of the most damaging pathogens in stone fruits. Researchers are exploring epiphytic and endophytic microorganisms with the potential to suppress pathogens, control pathogenic microorganisms, and/or promote plant growth. In this study, microorganisms with antagonistic activity against three Monilinia species were isolated from plum orchard soil and plum fruits. Antagonism tests in vitro showed strong antagonistic properties of six strains of bacteria and two yeast-like fungi against M. fructigena, M. fructicola, and M. laxa, with growth inhibition from 45.5 to 84.6%. The antagonists were identified and characterized at the genetic level using whole genome sequencing (WGS). Genes involved in antibiotic resistance, virulence, secondary metabolite synthesis, and plant growth promotion were identified and characterized through genome mapping, gene prediction, and annotation. None of the microorganisms studied were predicted to be pathogenic to humans. The results of this study indicate that the bacteria Bacillus pumilus, B. velezensis, two strains of Lysinibacillus agricola, Pseudomonas chlororaphis isolated from stone fruit orchard soil, and the yeast-like fungus Aureobasidium pullulans, isolated from plums, are promising candidates for the biological control of Monilinia spp. Full article