Bacillus B2 promotes root growth and enhances phosphorus absorption in apple rootstocks by affecting MhMYB15.

Due to the chelation of phosphorus in the soil, it becomes unavailable for plant growth and development. The mechanisms by which phosphorus-solubilizing bacteria activate immobilized phosphorus to promote the growth and development of woody plants, as well as the intrinsic molecular mechanisms, are not clear. Through the analysis of microbial communities in the rhizosphere 16S V3-V4 and a homologous gene encoding microbial alkaline phosphomonoesterase (phoD) in phosphate-efficient (PE) and phosphate-inefficient apple rootstocks, it was found that PE significantly enriched beneficial rhizobacteria. The best phosphorus-solubilizing bacteria, Bacillus sp. strain 7DB1 (B2), was isolated, purified, and identified from the rhizosphere soil of PE rootstocks. Incubating with Bacillus B2 into the rhizosphere of apple rootstocks significantly increased the soluble phosphorus and flavonoid content in the rhizosphere soil. Simultaneously, this process stimulates the root development of the rootstocks and enhances plant phosphorus uptake. After root transcriptome sequencing, candidate transcription factor MhMYB15, responsive to Bacillus B2, was identified through heatmap and co-expression network analysis. Yeast one-hybrid, electrophoretic mobility shift assay, and LUC assay confirmed that MhMYB15 can directly bind to the promoter regions of downstream functional genes, including chalcone synthase MhCHS2 and phosphate transporter MhPHT1;15. Transgenic experiments with MhMYB15 revealed that RNAi-MhMYB15 silenced lines failed to induce an increase in flavonoid content and phosphorus levels in the roots under the treatment of Bacillus B2, and plant growth was slower than the control. In conclusion, MhMYB15 actively responds to Bacillus B2, regulating the accumulation of flavonoids and the uptake of phosphorus, thereby influencing plant growth and development.

Genetic and Structural Analyses of RRNPP Intercellular Peptide Signaling of Gram-Positive Bacteria.

Bacteria use diffusible chemical messengers, termed pheromones, to coordinate gene expression and behavior among cells in a community by a process known as quorum sensing. Pheromones of many gram-positive bacteria, such as Bacillus and Streptococcus, are small, linear peptides secreted from cells and subsequently detected by sensory receptors such as those belonging to the large family of RRNPP proteins. These proteins are cytoplasmic pheromone receptors sharing a structurally similar pheromone-binding domain that functions allosterically to regulate receptor activity. X-ray crystal structures of prototypical RRNPP members have provided atomic-level insights into their mechanism and regulation by pheromones. This review provides an overview of RRNPP prototype signaling; describes the structure-function of this protein family, which is spread widely among gram-positive bacteria; and suggests approaches to target RRNPP systems in order to manipulate beneficial and harmful bacterial behaviors.

Genome-wide transformation reveals extensive exchange across closely related Bacillus species.

Bacterial transformation is an important mode of horizontal gene transfer that helps spread genetic material across species boundaries. Yet, the factors that pose barriers to genome-wide cross-species gene transfer are poorly characterized. Here, we develop a replacement accumulation assay to study the effects of genomic distance on transfer dynamics. Using Bacillus subtilis as recipient and various species of the genus Bacillus as donors, we find that the rate of orthologous replacement decreases exponentially with the divergence of their core genomes. We reveal that at least 96% of the B. subtilis core genes are accessible to replacement by alleles from Bacillus spizizenii. For the more distantly related Bacillus atrophaeus, gene replacement events cluster at genomic locations with high sequence identity and preferentially replace ribosomal genes. Orthologous replacement also creates mosaic patterns between donor and recipient genomes, rearranges the genome architecture, and governs gain and loss of accessory genes. We conclude that cross-species gene transfer is dominated by orthologous replacement of core genes which occurs nearly unrestricted between closely related species. At a lower rate, the exchange of accessory genes gives rise to more complex genome dynamics.

In silico biotechnological potential of Bacillus sp. strain MHSD_37 bacterial endophyte.

BACKGROUND: Endophytic bacteria possess a range of unique characteristics that enable them to successfully interact with their host and survive in adverse environments. This study employed in silico analysis to identify genes, from Bacillus sp. strain MHSD_37, with potential biotechnological applications. RESULTS: The strain presented several endophytic lifestyle genes which encode for motility, quorum sensing, stress response, desiccation tolerance and root colonisation. The presence of plant growth promoting genes such as those involved in nitrogen fixation, nitrate assimilation, siderophores synthesis, seed germination and promotion of root nodule symbionts, was detected. Strain MHSD_37 also possessed genes involved in insect virulence and evasion of defence system. The genome analysis also identified the presence of genes involved in heavy metal tolerance, xenobiotic resistance, and the synthesis of siderophores involved in heavy metal tolerance. Furthermore, LC-MS analysis of the excretome identified secondary metabolites with biological activities such as anti-cancer, antimicrobial and applications as surfactants. CONCLUSIONS: Strain MHSD_37 thereby demonstrated potential biotechnological application in bioremediation, biofertilisation and biocontrol. Moreover, the strain presented genes encoding products with potential novel application in bio-nanotechnology and pharmaceuticals.

Reclassification of the first Bacillus tropicus phage calls for reclassification of other Bacillus temperate phages previously designated as plasmids.

Bacillus tropicus is a recently identified subspecies of the Bacillus cereus group of bacteria that have been shown to possess genes associated with antimicrobial resistance (AMR) and identified as the causative agent for anthrax-like disease in Chinese soft-shelled turtles. In addition, B. tropicus has demonstrated great potential in the fields of bioremediation and bioconversion. This article describes the comparative genomics of a Bacillus phage vB_Btc-RBClinn15 (referred to as RBClin15) infecting the recently identified B. tropicus AOA-CPS1. RBClin15 is a temperate phage with a putative parABS partitioning system as well as an arbitrium system, which are presumed to enable extrachromosomal genome maintenance and regulate the lysis/lysogeny switch, respectively. The temperate phage RBClin15 has been sequenced however, was erroneously deposited as a plasmid in the NCBI GenBank database. A BLASTn search against the GenBank database using the whole genome sequence of RBClin15 revealed seven other putative temperate phages that were also deposited as plasmids in the database. Comparative genomic analyses shows that RBClin15 shares between 87 and 92% average nucleotide identity (ANI) with the seven temperate phages from the GenBank database. All together RBClin15 and the seven putative temperate phages share common genome arrangements and < 29% protein homologs with the closest phages, including 0105phi7-2. A phylogenomic tree and proteome-based phylogenetic tree analysis showed that RBClin15 and the seven temperate phages formed a separate branch from the closest phage, 0105phi7-2. In addition, the intergenomic similarity between RBClin15 and its closely related phages ranged between 0.3 and 47.7%. Collectively, based on the phylogenetic, and comparative genomic analyses, we propose three new species which will include RBClin15 and the seven temperate phages in the newly proposed genus Theosmithvirus under Caudoviricetes.

Phenotypic plasticity: The role of a phosphatase family Rap in the genetic regulation of Bacilli.

In the last two decades, an increasing number of bacterial species have been recognized that are able to generate a phenotypically diverse population that shares an identical genotype. This ability is dependent on a complex genetic regulatory network that includes cellular and environmental signals, as well as stochastic elements. Among Bacilli, a broadly distributed family of Rap (Response-regulator aspartyl phosphate) phosphatases is known to modulate the function of the main phenotypic heterogeneity regulators by controlling their phosphorylation. Even more, their related extracellular Phr (Phosphatase regulator) peptides function as signals, creating a cell-cell communication network that regulates the phenotypic development of the entire population. In this review, we examine the role that the Rap phosphatases and their Phr peptides play in the regulation of Bacillus subtilis phenotypic differentiation, and in other members of the Bacillus genus. We also highlight the contribution of these regulatory elements to the fitness of bacterial cells and mobile genetic elements, for example, prophages and conjugative vectors.

Liquorilactobacillus: A Context of the Evolutionary History and Metabolic Adaptation of a Bacterial Genus from Fermentation Liquid Environments.

In the present work, we carried out a comparative genomic analysis to trace the evolutionary trajectory of the bacterial species that make up the Liquorilactobacillus genus, from the identification of genes and speciation/adaptation mechanisms in their unique characteristics to the identification of the pattern grouping these species. We present phylogenetic relationships between Liquorilactobacillus and related taxa such as Bacillus, basal lactobacilli and Ligilactobacillus, highlighting evolutionary divergences and lifestyle transitions across different taxa. The species of this genus share a core genome of 1023 genes, distributed in all COGs, which made it possible to characterize it as Liquorilactobacillus sensu lato: few amino acid auxotrophy, low genes number for resistance to antibiotics and general and specific cellular reprogramming mechanisms for environmental responses. These species were divided into four clades, with diversity being enhanced mainly by the diversity of genes involved in sugar metabolism. Clade 1 presented lower (< 70%) average amino acid identity with the other clades, with exclusive or absent genes, and greater distance in the genome compared to clades 2, 3 and 4. The data pointed to an ancestor of clades 2, 3 and 4 as being the origin of the genus Ligilactobacillus, while the species of clade 1 being closer to the ancestral Bacillus. All these traits indicated that the species of clade 1 could be soon separated in a distinct genus.

How to identify and quantify the members of the Bacillus genus?

Members of the Bacillus genus are widely distributed throughout natural environments and have been studied for decades among others for their physiology, genetics, ecological functions, and applications. However, despite its prevalence in nature, the characterization and classification of Bacillus remain challenging due to its complex and ever-evolving taxonomic framework. This review addresses the current state of the Bacillus taxonomic landscape and summarizes the critical points in the development of Bacillus phylogeny. With a clear view of Bacillus phylogeny as a foundation, we subsequently review the methodologies applied in identifying and quantifying Bacillus, while also discussing their respective advantages and disadvantages.

A smart RBS library and its prediction model for robust and accurate fine-tuning of gene expression in Bacillus species.

Bacillus species, such as Bacillus subtilis and Bacillus licheniformis, are important industrial bacteria. However, there is a lack of standardized and predictable genetic tools for convenient and reproducible assembly of genetic modules in Bacillus species to realize their full potential. In this study, we constructed a Ribosome Binding Site (RBS) library in B. licheniformis, which provides incremental regulation of expression levels over a 104-fold range. Additionally, we developed a model to quantify the resulting translation rates. We successfully demonstrated the robust expression of various target genes using the RBS library and showed that the model accurately predicts the translation rates of arbitrary coding genes. Importantly, we also extended the use of the RBS library and prediction model to B. subtilis, B. thuringiensis, and B. amyloliquefacie. The versatility of the RBS library and its prediction model enables quantification of biological behavior, facilitating reliable forward engineering of gene expression.

The effect of seed germination and Bacillus spp. on the ripening of plant cheese analogs.

Consumer demand for plant cheeses is increasing, but challenges of improving both flavor and quality remain. This study investigated the microbiological and physicochemical impact of seed germination and fermentation with Bacillus velezensis and Bacillus amyloliquefaciens on the ripening of plant cheese analogs. Chlorine treatment or addition of Lactiplantibacillus plantarum and Lactococcus lactis controlled microbial growth during seed germination. Lp. plantarum and Lc. lactis also served as starter cultures for the acidification of soy and lupine milk and were subsequently present in the unripened plant cheese as dominant microbes. Acidification also inhibited the growth and metabolic activity of bacilli but Bacillus spores remained viable throughout ripening. During plant cheese ripening, Lc. lactis was inactivated before Lp. plantarum and the presence of bacilli during seed germination delayed Lc. lactis inactivation. Metagenomic sequencing of full-length 16S rRNA gene amplicons confirmed that the relative abundance of the inoculated strains in each ripened cheese sample exceeded 99%. Oligosaccharides including raffinose, stachyose, and verbascose were rapidly depleted in the initial stage of ripening. Both germination and the presence of bacilli during seed germination had impact on polysaccharide hydrolysis during ripening. Bacilli but not seed germination enhanced proteolysis of plant cheese during ripening. In conclusion, the use of germination with lactic acid bacteria in combination with Bacillus spp. exhibited the potential to improve the quality of ripened plant cheeses with a positive effect on the reduction of hygienic risks. IMPORTANCE: The development of novel plant-based fermented food products for which no traditional templates exist requires the development of starter cultures. Although the principles of microbial flavor formation in plant-based analogs partially overlap with dairy fermentations, the composition of the raw materials and thus likely the selective pressure on the activity of starter cultures differs. Experiments that are described in this study explored the use of seed germination, the use of lactic acid bacteria, and the use of bacilli to reduce hygienic risks, to acidify plant milk, and to generate taste-active compounds through proteolysis and fermentative conversion of carbohydrates. The characterization of fermentation microbiota by culture-dependent and culture-independent methods also confirmed that the starter cultures used were able to control microbial communities throughout 90 d of ripening. Taken together, the results provide novel tools for the development of plant-based analogs of fermented dairy products.

Insights into the genomic and phenotypic characteristics of Bacillus spp. strains isolated from biofilms in broiler farms.

The characterization of surface microbiota living in biofilms within livestock buildings has been relatively unexplored, despite its potential impact on animal health. To enhance our understanding of these microbial communities, we characterized 11 spore-forming strains isolated from two commercial broiler chicken farms. Sequencing of the strains revealed them to belong to three species Bacillus velezensis, Bacillus subtilis, and Bacillus licheniformis. Genomic analysis revealed the presence of antimicrobial resistance genes and genes associated with antimicrobial secretion specific to each species. We conducted a comprehensive characterization of the biofilm formed by these strains under various conditions, and we revealed significant structural heterogeneity across the different strains. A macro-colony interaction model was employed to assess the compatibility of these strains to coexist in mixed biofilms. We identified highly competitive B. velezensis strains, which cannot coexist with other Bacillus spp. Using confocal laser scanning microscopy along with a specific dye for extracellular DNA, we uncovered the importance of extracellular DNA for the formation of B. licheniformis biofilms. Altogether, the results highlight the heterogeneity in both genome and biofilm structure among Bacillus spp. isolated from biofilms present within livestock buildings.IMPORTANCELittle is known about the microbial communities that develop on farms in direct contact with animals. Nonpathogenic strains of Bacillus velezensis, Bacillus subtilis, and Bacillus licheniformis were found in biofilm samples collected from surfaces in contact with animals. Significant genetic and phenotypic diversity was described among these Bacillus strains. The strains do not possess mobile antibiotic resistance genes in their genomes and have a strong capacity to form structured biofilms. Among these species, B. velezensis was noted for its high competitiveness compared with the other Bacillus spp. Additionally, the importance of extracellular DNA in the formation of B. licheniformis biofilms was observed. These findings provide insights for the management of these surface microbiota that can influence animal health, such as the use of competitive strains to minimize the establishment of undesirable bacteria or enzymes capable of specifically deconstructing biofilms.

Complete genome sequence of Bacillus velezensis strain Ag109, a biocontrol agent against plant-parasitic nematodes and Sclerotinia sclerotiorum.

Soybean is the main oilseed cultivated worldwide. Even though Brazil is the world's largest producer and exporter of soybean, its production is severely limited by biotic factors. Soil borne diseases are the most damaging biotic stressors since they significantly reduce yield and are challenging to manage. In this context, the present study aimed to evaluate the potential of a bacterial strain (Ag109) as a biocontrol agent for different soil pathogens (nematodes and fungi) of soybean. In addition, the genome of Ag109 was wholly sequenced and genes related to secondary metabolite production and plant growth promotion were mined. Ag109 showed nematode control in soybean and controlled 69 and 45% of the populations of Meloidogyne javanica and Pratylenchus brachyurus, respectively. Regarding antifungal activity, these strains showed activity against Macrophomia phaseolina, Rhizoctonia solani, and Sclerotinia sclerotiorum. For S. sclerotiorum, this strain increased the number of healthy plants and root dry mass compared to the control (with inoculation). Based on the average nucleotide identity and digital DNA-DNA hybridization, this strain was identified as Bacillus velezensis. Diverse clusters of specific genes related to secondary metabolite biosynthesis and root growth promotion were identified, highlighting the potential of this strain to be used as a multifunctional microbial inoculant that acts as a biological control agent while promoting plant growth in soybean.

Emergence of multidrug-resistant Bacillus spp. derived from animal feed, food and human diarrhea in South-Eastern Bangladesh.

BACKGROUND: Antimicrobial resistance poses a huge risk to human health worldwide, while Bangladesh is confronting the most severe challenge between the food supply and the huge consumption of antibiotics annually. More importantly, probiotics containing Bacillus spp. are claimed to be an alternative to antimicrobial stewardship programs. However, their antibiotic resistance remains elusive. Thus, we employed the antimicrobial susceptibility test and PCR to assess the prevalence of resistance, including multidrug resistance (MDR) and resito-genotyping of isolated Bacillus spp. RESULTS: The phenotypic profile showed that Bacillus spp. were 100% sensitive to gentamicin (2 µg/mL), whereas lowered sensitivity to levofloxacin (67.8%, 0.5-1 µg/mL), ciprofloxacin (62.3%, 0.5-1 µg/mL), clindamycin (52.2%, 0.25-0.5 µg/mL), amoxicillin-clavulanic acid (37.6%, 0.06 µg/mL), azithromycin (33.4%, 1-2 µg/mL), tetracycline (25.6%, 2-4 µg/mL), nitrofurantoin (21.1%, 16-32 µg/mL), co-trimoxazole (19.2%, 2 µg/mL), and erythromycin (18.8%, 0.25-0.5 µg/mL). The strains were completely resistant to penicillin, amoxicillin-clavulanic acid, cefixime, ceftriaxone, vancomycin, and co-trimoxazole, and a species-specific trend was seen in both phenotypic and genotypic resistance patterns. Genotypic resistance indicated prevalence of the bla1 (71.5%), tetA (33%), erm1 (27%), blaTEM (13.1%), blaCTX-M-1/blaCTX-M-2 /sul1 (10.1%), blaSHV (9.6%), and qnrS (4.1%) genes. The ß-lactamase resistance gene bla1 was found in all penicillin-resistant (MIC ≥ 32 µg/mL) Bacillus spp. One hundred ninety-one isolates (89.6%) were MDR, with 100% from diarrhea, 90.3% from food, and 88.7% from animal feed. CONCLUSION: Based on the MIC value and profile analysis of antibiotic resistance genes, this is the first study that Bacillus spp. antimicrobial susceptibilities have been identified in Bangladesh, and our study will shed light on the adverse effects of feed-borne Bacillus spp. emerging from animal feed to the food chain. A comprehensive investigation is urgently needed by policymakers on tolerance limits and harmful effects in the animal industry.

Lipopeptides from Bacillus velezensis ZLP-101 and their mode of action against bean aphids Acyrthosiphon pisum Harris.

BACKGROUND: Natural products are important sources for the discovery of new biopesticides to control the worldwide destructive pests Acyrthosiphon pisum Harris. Here, insecticidal substances were discovered and characterized from the secondary metabolites of the bio-control microorganism Bacillus velezensis strain ZLP-101, as informed by whole-genome sequencing and analysis. RESULTS: The genome was annotated, revealing the presence of four potentially novel gene clusters and eight known secondary metabolite synthetic gene clusters. Crude extracts, prepared through ammonium sulfate precipitation, were used to evaluate the effects of strain ZLP-101 on Acyrthosiphon pisum Harris aphid pests via exposure experiments. The half lethal concentration (LC50) of the crude extract from strain ZLP-101 against aphids was 411.535 mg/L. Preliminary exploration of the insecticidal mechanism revealed that the crude extract affected aphids to a greater extent through gastric poisoning than through contact. Further, the extracts affected enzymatic activities, causing holes to form in internal organs along with deformation, such that normal physiological activities could not be maintained, eventually leading to death. Isolation and purification of extracellular secondary metabolites were conducted in combination with mass spectrometry analysis to further identify the insecticidal components of the crude extracts. A total of 15 insecticidal active compounds were identified including iturins, fengycins, surfactins, and spergualins. Further insecticidal experimentation revealed that surfactin, iturin, and fengycin all exhibited certain aphidicidal activities, and the three exerted synergistic lethal effects. CONCLUSIONS: This study improved the available genomic resources for B. velezensis and serves as a foundation for comprehensive studies of the insecticidal mechanism by Bacillus velezensis ZLP-101 in addition to the active components within biological control strains.

Mechanisms of ROS-mediated interactions between Bacillus aryabhattai LAD and maize roots to promote plant growth.

BACKGROUND: Plant growth-promoting rhizobacteria (PGPR), as a group of environmentally friendly bacteria growing in the rhizosphere of plants, play an important role in plant growth and development and resistance to environmental stresses. However, their limited understanding has led to the fact that their large-scale use in agriculture is still scarce, and the mechanisms by which beneficial bacteria are selected by plants and how they interact with them are still unclear. METHOD: In this study, we investigated the interaction between the auxin-producing strain Bacillus aryabhattai LAD and maize roots, and performed transcriptomic and metabolomic analyses of Bacillus aryabhattai LAD after treatment with maize root secretions(RS). RESULTS: Our results show that there is a feedback effect between the plant immune system and bacterial auxin. Bacteria activate the immune response of plant roots to produce reactive oxygen species(ROS), which in turn stimulates bacteria to synthesize IAA, and the synthesized IAA further promotes plant growth. Under the condition of co-culture with LAD, the main root length, seedling length, root surface area and root volume of maize increased by 197%, 107%, 89% and 75%, respectively. In addition, the results of transcriptome metabolome analysis showed that LAD was significantly enriched in amino acid metabolism, carbohydrate metabolism and lipid metabolism pathways after RS treatment, including 93 differentially expressed genes and 45 differentially accumulated metabolites. CONCLUSION: Our findings not only provide a relevant model for exploring the effects of plant-soil microbial interactions on plant defense functions and thereby promoting plant growth, but also lay a solid foundation for the future large-scale use of PGPR in agriculture for sustainable agricultural development.

Biocontrol Potential of Bacillus strains against soybean cyst nematode (Heterodera glycines) and for promotion of soybean growth.

The soybean cyst nematode (SCN, Heterodera glycines) is the most yield-limiting pathogen in soybeans worldwide. Using chemical pesticides to control this disease is harmful to human and environment. It is urgent to develop environment-friendly nematicides. The aim of this study was to discover novel biocontrol agents on H. glycines control and soybean growth under greenhouse and field conditions Eight Bacillus strains were isolated from soil rhizosphere soils and the stability and efficiency of H. glycines was assessed in greenhouse and field experiments in 2021 and 2022. In particular, the Ba2-6 strain had the highest potential, because it was a biocontrol agent against H. glycines shown to cause 93.85% juvenile mortality. Furthermore, strains Ba 1-7, Ba2-4, and Ba2-6 effectively reduced the number of females and improved the soybean seed number per plant. Based on their morphological, physiological, biochemical and molecular (16 S rRNA) characteristics, the three strains were identified as B. aryabhattai (Ba1-7), B. megatherium (Ba2-4), and B. halotolerans (Ba2-6). The ability of Ba2-6 to induce systemic resistance to H. glycines in soybeans was investigated by the split-root system and real-time quantitative PCR experiments. The results indicated that the Ba2-6 strain induced systemic resistance to suppress the penetration of H. glycines, and enhanced gene expression of PR1, PR3a, PR5, and NPR1-2, involved in the salicylic acid and jasmonic acid pathways. The study suggests that the strains of B. aryabhattai Ba1-7, B. megatherium Ba2-4, and B. halotolerans Ba2-6 can be considered as effective biocontrol agents to control H. glycines. Further, B. halotolerans Ba2-6 not only promotes soybean growth but also enhances resistance to H. glycines by regulating defense-related gene expression and inducing systemic resistance in soybean.

Production and optimization of surfactin produced from locally isolated Bacillus halotolerans grown on agro-industrial wastes and its antimicrobial efficiency.

INTRODUCTION: Optimal exploitation of the huge amounts of agro-industrial residuals that are produced annually, which endangers the ecosystem and ultimately contributes to climate change, is one of the solutions available to produce value-added compounds. AIM AND OBJECTIVES: This study aimed at the economic production and optimization of surfactin. Therefore, the production was carried out by the microbial conversion of Potato Peel Waste (PPW) and Frying Oil Waste (FOW) utilizing locally isolated Bacillus halotolerans. Also, investigating its potential application as an antimicrobial agent towards some pathogenic strains. RESULTS: Screening the bacterial isolates for surfactin production revealed that the strain with the highest yield (49 g/100 g substrate) and efficient oil displacement activity was genetically identified as B. halotolerans. The production process was then optimized utilizing Central Composite Design (CCD) resulting in the amelioration of yield by 11.4% (from 49 to 55.3 g/100 g substrate) and surface tension (ST) by 8.3% (from 36 to 33 mN/m) with a constant level of the critical micelle concentration (CMC) at 125 mg/L. Moreover, the physiochemical characterization studies of the produced surfactin by FTIR, 1H NMR, and LC-MS/MS proved the existence of a cyclic lipopeptide (surfactin). The investigations further showed a strong emulsification affinity for soybean and motor oil (E24 = 50%), as well as the ability to maintain the emulsion stable over a wide pH (4-10) and temperature (10-100 °C) range. Interestingly, surfactin had a broad-spectrum range of inhibition activity against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, klebsiella pneumonia, and Candida albicans. CONCLUSION: Subsequently, the screening of the isolates and the utilized food-processing wastes along with the extraction technique resulted in a high yield of surfactin characterized by acceptable ST and CMC levels. However, optimization of the cultural conditions to improve the activity and productivity was achieved using Factor-At-A-Time (OFAT) and Central Composite Design (CCD). In contrast, surface activity recorded a maximum level of (33 mN/n) and productivity of 55.3 g/100 g substrate. The optimized surfactin had also the ability to maintain the stability of emulsions over a wide range of pH and temperature. Otherwise, the obtained results proved the promising efficiency of the surfactin against bacterial and fungal pathogens.

Pseudomonas ZY-1 and Bacillus FY-1 protecting the rice seedlings from the harm of Pseudomonas aeruginosa via indirect seawead lysis.

The local ecosystems, fishery and human health are all threatened by water blooms, so effectively controlling water blooms has become an urgent and challenging issue. Biological control of water blooms is given priority due to its low cost, high efficiency and environmental friendliness. In this study, Pseudomonas ZY-1 and Bacillus FY-1, two highly-effective algicidal bacteria strains which are able to indirectly lyse algae by separating and screening from the vigorous water body in the paddy alga of Northeast China were obtained. The two bacterial strains have stronger ability to lyse alga in the bacterial liquid concentration of 106 CFU/ml, and the alga-lysing rate on 7 d reached 84.03% and 83.11% respectively. The active substance secreted by ZY-1 is not sensitive to the changes of temperature and pH value, while as FY-1 cell-free filtrate is not stable in high temperature above 50 ℃ and pH of 5, it requires the sun light to have the algaecidal effect. The cell-free filtrates of strains ZY-1 and FY-1 had the best lysis effect on Microcystis aeruginosa cells, and the chlorophyll a content of algae decreased to 0.13 ± 0.02 mg/L and 0.14 ± 0.03 mg/L respectively and the Fv/Fm of Microcystis aeruginosa decreased by 97.22% after 7 days. The algaecidal process of ZY-1 and FY-1 may be that the cell-free filtrate inhibits the photosynthesis of Microcystis aeruginosa, and meanwhile it avoids the regeneration and repair of photosynthesis of algal cells by affecting the gene expression and damaging the repair system of algal cells, so the membrane lipid peroxidation is exacerbated and then the membrane of algal cells is broken, the algal cells can't do normal life activities, and finally the algal cell would be killed. The rice seedlings in the algal liquid treatment group are short and show root dysplasia, few roots and brown roots. After treated with cell-free filtrate of ZY-1 and FY-1, the oxidative damage of the rice is obviously reduced, and the harm from Microcystis aeruginosa is reduced, which has the repair effect to the roots of rice seedlings and its aboveground growth. The cell-free filtrate of FY-1 works better than ZY-1. The bacteria strains of ZY-1 and FY-1 have the indirect algaecide trait, which makes them the potential environmentally-friendly algaecidal bacteria and they show broad application in the agricultural production and the control of water blooms.

The beneficial rhizobacterium Bacillus velezensis SQR9 regulates plant nitrogen uptake via an endogenous signaling pathway.

Nitrogen fertilizer is widely used in agriculture to boost crop yields. Plant growth-promoting rhizobacteria (PGPRs) can increase plant nitrogen use efficiency through nitrogen fixation and organic nitrogen mineralization. However, it is not known whether they can activate plant nitrogen uptake. In this study, we investigated the effects of volatile compounds (VCs) emitted by the PGPR strain Bacillus velezensis SQR9 on plant nitrogen uptake. Strain SQR9 VCs promoted nitrogen accumulation in both rice and Arabidopsis. In addition, isotope labeling experiments showed that strain SQR9 VCs promoted the absorption of nitrate and ammonium. Several key nitrogen-uptake genes were up-regulated by strain SQR9 VCs, such as AtNRT2.1 in Arabidopsis and OsNAR2.1, OsNRT2.3a, and OsAMT1 family members in rice, and the deletion of these genes compromised the promoting effect of strain SQR9 VCs on plant nitrogen absorption. Furthermore, calcium and the transcription factor NIN-LIKE PROTEIN 7 play an important role in nitrate uptake promoted by strain SQR9 VCs. Taken together, our results indicate that PGPRs can promote nitrogen uptake through regulating plant endogenous signaling and nitrogen transport pathways.

Isolation and identification of NEAU-CP5: A seed-endophytic strain of B. velezensis that controls tomato bacterial wilt.

Bacterial wilt of tomato caused by Ralstonia solanacearum is a critical soilborne disease that drastically reduces yield. In the current study, an endophytic strain NEAU-CP5 with strong antagonistic activity against R. solanacearum was isolated from tomato seeds and characterized. The strain was identified as Bacillus velezensis based on 16S rRNA gene and whole genome sequence analysis. NEAU-CP5 can secrete amylase, protease, and cellulase, and also produce known antibacterial metabolites, including cyclo (leucylprolyl), cyclo (phenylalanyl-prolyl), cyclo (Pro-Gly), 3-benzyl-2,5-piperazinedione, pentadecanoic acid, eicosane, 2-methyoic acid, isovaleric acid, dibuty phthalate, and esters of fatty acids (HFDU), which may be responsible for its strong antibacterial activity. Fourteen gene clusters associated with antibacterial properties were also identified in the whole genome sequence of NEAU-CP5. Pot experiment demonstrated that the application of 108 CFU/mL NEAU-CP5 on tomato plants significantly reduced the incidence of tomato bacterial wilt by 68.36 ± 1.67 %. NEAU-CP5 also increased the activity of defense-related enzymes (CAT, POD, PPO, SOD, and PAL) in tomato plants. This is the first report of an effective control of bacterial wilt on tomato plants by B. velezensis and highlights the potential of NEAU-CP5 as a potential biocontrol agent for the management of tomato bacterial wilt.