Antibacterial and antitumor activity of Bogorol B-JX isolated from Brevibacillus laterosporus JX-5

Evaluation of probiotic properties of a Brevibacillus laterosporus strain

Brevibacillus laterosporus is a strain of probiotic bacteria that has been widely used in pest control, cash crop, and other production areas. However, few studies have been conducted on its use as a feed additive in animals. Therefore, the probiotic potential of B. laterosporus PBC01 was evaluated by characterizing hydrophobicity, auto-aggregation activity, bile salt and simulated gastrointestinal fluid tolerance, bienzymatic, and antibacterial activity. Antibiotic susceptibility, hemolysis assays, and supplemental feeding of mice were also performed to evaluate safety features. Our results showed that B. laterosporus PBC01 had moderate hydrophobicity, high auto-agglutination ability. Meanwhile, B. laterosporus PBC01 had good tolerance to bile salt and simulated gastrointestinal fluid. It had the ability to secrete protease, cellulase, and to inhibit various pathogens. In addition, B. laterosporus PBC01 was sensitive to many antibiotics, and did not produce hemolysin. In the safety assessment of mice, it did not cause any deaths, nor did it affect the cell components of blood, antioxidant capacity, and reproductive health. The study indicated the great probiotic characteristics and safety of B. laterosporus PBC01. This may provide a theoretical basis for the clinical application and development of probiotic-based feed additives.

Action mechanism of the potential biocontrol agent Brevibacillus laterosporus SN19-1 against Xanthomonas oryzae pv. oryzae causing rice bacterial leaf blight

The causal agent of rice bacterial leaf blight (BLB) is Xanthomonas oryzae pv. oryzae (Xoo), which causes serious damage to rice, leading to yield reduction or even crop failure. Brevibacillus laterosporus SN19-1 is a biocontrol strain obtained by long-term screening in our laboratory, which has a good antagonistic effect on a variety of plant pathogenic bacteria. In this study, we investigated the efficacy and bacterial inhibition of B. laterosporus SN19-1 against BLB to lay the theoretical foundation and research technology for the development of SN19-1 as a biopesticide of BLB. It was found that SN19-1 has the ability to fix nitrogen, detoxify organic phosphorus, and produce cellulase, protease, and siderophores, as well as IAA. In a greenhouse pot experiment, the control efficiency of SN19-1 against BLB was as high as 90.92%. Further investigation of the inhibitory mechanism of SN19-1 on Xoo found that the biofilm formation ability of Xoo was inhibited and the pathogenicity was weakened after the action of SN19-1 sterile supernatant on Xoo. The activities of enzymes related to respiration and the energy metabolism of Xoo were significantly inhibited, while the level of intracellular reactive oxygen species was greatly increased. Scanning electron microscopy observations showed folds on the surface of Xoo. A significant increase in cell membrane permeability and outer membrane permeability and a decrease in cell membrane fluidity resulted in the extravasation of intracellular substances and cell death. The results of this study highlight the role of B. laterosporus SN19-1 against the pathogen of BLB and help elucidate the underlying molecular mechanisms.

Novel Property Cytotoxicity and Mechanism of Food Preservative Brevilaterins against Human Gastric Cancer Cells

Brevilaterins, antimicrobial peptides produced by Brevibacillus laterosporus, are regarded as excellent food preservatives and are popular as antimicrobial applications. Recent research has uncovered their potent cytotoxic effects against diverse cancer cells, thereby underscoring the pressing need for more extensive and intensive investigations into this use. In this study, we explored their novel function in inducing cytotoxicity to cancer cells and systematically investigated the mechanism of action of Brevilaterin B/C (BB/BC) in vivo. Proliferation, membrane permeability, and apoptotic rate were evaluated using CCK-8 assay, LDH assay, and Annexin V-FITC/PI kits. ROS levels and mitochondrial membrane potential were detected using the fluorescent probe DCFH-DA and JC-1. Our results demonstrated that both BB and BC at concentrations of 4-6 µg/mL significantly inhibited the proliferation and migration of gastric cancer cells BGC-823. Treatment with 4 µg/mL of BB/BC rapidly increased LDH levels in the supernatant of BGC-823 cells, leading to further investigation of the mechanism of apoptosis. We found that the apoptotic rate of BGC-823 cells significantly increased upon treatment with BB/BC, demonstrating their potent induction of apoptosis. BB/BC-induced ROS production in BGC-823 cells impaired their growth and induced apoptosis, indicating a close association between apoptosis and ROS elevation. Additionally, JC-1 aggregates rapidly accumulated after treatment with 4 µg/mL of BB/BC, suggesting changes in mitochondrial membrane potential and early apoptosis. Taken together, our findings revealed that BB and BC exhibit significant anticancer effects against gastric cancer cells, highlighting the promising potential of Brevilaterins as anticancer agents.

Structural Diversity, LC-MS-MS Analysis and Potential Biological Activities of Brevibacillus laterosporus Extract

Lake Mariout is Egypt's degraded coastal marine habitat that encompasses a variety of wastes. The biodiversity and hard environmental conditions allow the co-existence of organisms with high resistance and rich metabolism, making them potential candidates for screening and isolating novel microbial strains. A bacterial isolate (BF202) cultured from the marine sediments of Alexandria's Mariout Lake (Egypt) was tested for its antimicrobial and anticancer potential. The phylogenetic analysis of the isolated strain's 16S rDNA and gyrB revealed that BF202 belongs to Brevibacillus laterosporus (B. laterosporus). Antibiosis of B. laterosporus was confirmed against microbial pathogens including Escherichia coli, Klebsiella pneumoniae, Salmonella typhi, and Staphylococcus aureus. The highest antibacterial activity was detected on glucose peptone medium after 18 h of incubation at 35 °C, and at pH of 7.0 in the presence of mannose and ammonium carbonate as carbon and nitrogen sources, respectively. The cytotoxicity of the methanolic extract against breast cancer (MCF-7) and normal Vero cell lines, using the MTT test, revealed IC50 values of 7.93 and 23.79 µg/mL, respectively. To identify apoptotic and necrotic cells, a flow cytometric analysis using annexin V-FITC/PI dual-labeling was utilized and recorded a higher number of necrotic cells compared to apoptotic ones. Similarly, the cell cycle S-phase arrest was reported. The LC-MS-MS investigation of B. laterosporus extract and the molecular networking database analysis demonstrated five strategic diketopiperazine compounds with antimicrobial and anticancer activities. Taken together, this research shows that the crude extract of B. laterosporus might be an effective agent against drug-resistant bacteria and malignant disorders due to its richness in diketopiperazines.

Antimicrobial Peptides Mediate Apoptosis by Changing Mitochondrial Membrane Permeability

Changes in mitochondrial membrane permeability are closely associated with mitochondria-mediated apoptosis. Antimicrobial peptides (AMPs), which have been found to enter cells to exert physiological effects, cause damage to the mitochondria. This paper reviews the molecular mechanisms of AMP-mediated apoptosis by changing the permeability of the mitochondrial membrane through three pathways: the outer mitochondrial membrane (OMM), inner mitochondrial membrane (IMM), and mitochondrial permeability transition pore (MPTP). The roles of AMPs in inducing changes in membrane permeability and apoptosis are also discussed. Combined with recent research results, the possible application prospects of AMPs are proposed to provide a theoretical reference for the development of AMPs as therapeutic agents for human diseases.

Underexplored bacteria as reservoirs of novel antimicrobial lipopeptides

Natural products derived from microorganisms play a prominent role in drug discovery as potential anti-infective agents. Over the past few decades, lipopeptides produced by particularly Bacillus, Pseudomonas, Streptomyces, Paenibacillus, and cyanobacteria species, have been extensively studied for their antimicrobial potential. Subsequently, daptomycin and polymyxin B were approved by the Food and Drug Administration as lipopeptide antibiotics. Recent studies have however, indicated that Serratia, Brevibacillus, and Burkholderia, as well as predatory bacteria such as Myxococcus, Lysobacter, and Cystobacter, hold promise as relatively underexplored sources of novel classes of lipopeptides. This review will thus highlight the structures and the newly discovered scaffolds of lipopeptide families produced by these bacterial genera, with potential antimicrobial activities. Additionally, insight into the mode of action and biosynthesis of these lipopeptides will be provided and the application of a genome mining approach, to ascertain the biosynthetic gene cluster potential of these bacterial genera (genomes available on the National Center for Biotechnology Information) for their future pharmaceutical exploitation, will be discussed.

Brevilaterin B from Brevibacillus laterosporus has selective antitumor activity and induces apoptosis in epidermal cancer

Brevilaterins as antimicrobial peptides (AMPs) secreted by a newly discovered species Brevibacillus laterosporus, had been demonstrated to display excellent antibacterial and antifungal activities; however, very limited information about their new bioactivity was ever developed. Herein, we discovered Brevilaterin B, an AMP produced by Br. laterosporus S62-9, exhibited a new anticancer activity and investigated its anticancer details. Proliferation, membrane permeability and apoptotic rate of cell lines were studied by methods of CCK-8 Assay, LDH Assay and Annexin V-FITC/PI Kits, respectively. ROS levels and mitochondrial membrane potential of tested cells were further detected through the fluorescent probes DCFH-DA and JC-1. Brevilaterin B exhibited broad-spectrum anticancer activity in a dose-dependent manner. It selectively inhibited the proliferation of epidermal cancer cell A431 but had no effect on its control normal cells in a dose of 2.0 µg/mL. In comparision, typical morphological characteristics of apoptosis and an apoptotic ratio of 71.0% in A431 were observed after treatment by 2.0-3.0 µg/mL of Brevilaterin B. The ROS levels increased by 21.3% and mitochondrial membrane potential reduced by 48.8% from A431 were further occurred, indicating Brevilaterin B's anticancer action was mainly focus on the mitochondrion of cancer cells. In total, Brevilaterin B we reported above maybe believed to be a potential application as an anticancer medicament, increasing its commercial value.

Broad-spectrum cytotoxicity to cancer cells of Brevilaterin C from Brevibacillus laterosporus and its specific mechanism on human epidermal cancer cells

Antimicrobial peptides (AMP) from Brevibacillus laterosporus have good prospects as clinical treatments for cancer. Nevertheless, details about their anticancer spectrum and mode of cytotoxicity remain poorly understood. A newly found AMP (named Brevilaterin C) secreted by B. laterosporus S62-9 exhibited strong inhibition on almost cancer cell lines examined at a concentration of 8 µg/ml but was relatively safe for normal cells. We further systematically examined its cytotoxicity and mechanism toward human epidermal cancer cell A431. A dosage of 3 µg/ml of Brevilaterin C could significantly increase lactate dehydrogenase release of tumor cells. Moreover, it could remarkably increase the ratio of apoptosis and reactive oxygen species generation of A431, indicating effective induction of apoptosis. Moreover, the formation of JC-1 aggregates was effectively prevented by a low concentration of Brevilaterin C, indicating its effective induction of A431's apoptosis. Brevilaterin C exhibited broad-spectrum cytotoxicity to cancer cells, indicating a good potential prospect in the medical field.

BLB8, an antiviral protein from Brevibacillus laterosporus strain B8, inhibits Tobacco mosaic virus infection by triggering immune response in tobacco

BACKGROUND

Tobacco mosaic virus (TMV) is one of destructive plant viruses, causing serious economic losses in the world. Using antiviral proteins or elicitors to inhibit viral infection or promote plant immunity is one of the efficient strategies against TMV. Our previous study identified that the fermentation broth of Brevibacillus laterosporus strain B8 showed strong antiviral activity against TMV. However, the active antiviral ingredient is still unclear.

RESULTS

Here, BLB8 (B. laterosporus strain B8 protein, BLB8), an antiviral protein from B. laterosporus strain B8 was isolated and characterized. BLB8 showed protective, inactive and curative effects against TMV, and the inhibition rate reached up to 63%, 83% and 55%, respectively. BLB8 infiltrated around the infection site of the recombinant virus TMV-GFP inhibited the systemic extend and movement of TMV. Pretreatment of the bottom leaves with BLB8 inhibited the spread and accumulation of TMV in upper systemic leaves. Furthermore, BLB8 caused hypersensitive response (HR) in a dose-dependent way, promoted H2 O2 accumulation, and induced the expression of defense-relative genes in Nicotiana benthamiana.

CONCLUSION

The antiviral protein BLB8 from B. laterosporus strain B8 effectively inhibits TMV infection in inactivation, protective and curative effects through triggering plant immunity in tobacco. Therefore, the present study provides a new antiviral agent for prevention and control of viral disease. © 2021 Society of Chemical Industry.

Antibacterial mechanism of brevilaterin B: an amphiphilic lipopeptide targeting the membrane of Listeria monocytogenes

Antimicrobial peptides (AMPs) are recognized as promising safe alternatives to antibiotics for its low drug-resistance. Brevilaterin B, a newly discovered antimicrobial lipopeptide produced by Brevibacillus laterosporus S62-9, exhibits efficient antibacterial activity on Listeria monocytogenes with a minimum inhibitory concentration of 1 μg mL^-1. The present research aimed to investigate the antibacterial mechanism of brevilaterin B against Listeria monocytogenes. Brevilaterin B caused membrane depolarization and the breakup of the cytomembrane as measured by 3,3-dipropylthiadicarbocyanine iodide and transmission electron microscopy, respectively. Using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt (7:3) as a model membrane, results proved that brevilaterin B could bind to liposomes, integrate into the lipid bilayer, and consequently increase the permeability of liposomes to calcein. The secondary structure of brevilaterin B also changed from an unstructured coil to a mainly β-sheet conformation as measured by circular dichroism. Brevilaterin B exhibits antibacterial activity by a membrane interaction mechanism, which provides a theoretical basis for using brevilaterin B as a promising natural and effective antimicrobial agent against pathogenic bacteria. KEY POINTS: • Brevilaterin B exhibited antibacterial activity against Listeria monocytogenes. • Brevilaterin B exhibited membrane interaction mechanism. • Brevilaterin B showed conformational change when interacted with liposome.

Recent Advancements in the Development of Modern Probiotics for Restoring Human Gut Microbiome Dysbiosis

A healthy gut is predominantly occupied by bacteria which play a vital role in nutrition and health. Any change in normal gut homeostasis imposes gut dysbiosis. So far, efforts have been made to mitigate the gastrointestinal symptoms using modern day probiotics. The majority of the probiotics strains used currently belong to the genera Lactobacillus, Clostridium, Bifidobacterium and Streptococcus. Recent advancements in culturomics by implementing newer techniques coupled with the use of gnotobiotic animal models provide a subtle ground to develop novel host specific probiotics therapies. In this review article, the recent advances in the development of microbe-based therapies which can now be implemented to treat a wide spectrum of diseases have been discussed. However, these probiotics are not classified as drugs and there is a lack of stringent law enforcement to protect the end users against the pseudo-probiotic products. While modern probiotics hold strong promise for the future, more rigorous regulations are needed to develop genuine probiotic products and characterize novel probiotics using the latest research and technology. This article also highlights the possibility of reducing antibiotic usage by utilizing probiotics developed using the latest concepts of syn and ecobiotics.

Rapid polymerase chain reaction assays for Brevibacillus laterosporus detection

The identification of the ubiquitous spore-forming bacterium Brevibacillus laterosporus, whose interest in pharma, agriculture, and other industrial sectors is raising, mostly relies on 16S ribosomal RNA gene sequence analysis. However, due to bacterial gene homology, this method appears insufficient for a proper discrimination of this species, so that the availability of other target genes is necessary. Leveraging the morphological and genetic feature uniqueness of B. laterosporus, a sensitive and reliable detection and quantification method based on polymerase chain reaction (PCR) and quantitative PCR assays, respectively, was developed. Targeting a highly conserved spore surface protein-related gene, B. laterosporus could be easily found in different matrices including soil, food, and insect body. Primer set selectivity was confirmed to be very specific and no false positives or negatives were observed using DNA of different bacterial species as a template. The method developed is also suitable for the rapid identification of newly isolated B. laterosporus strains.