Isolation and Structural Elucidation of Brevibacillin, an Antimicrobial Lipopeptide from Brevibacillus laterosporus That Combats Drug-Resistant Gram-Positive Bacteria

Characterization of bacteriocin produced by Brevibacillus laterosporus Tk3 isolated from 'tatwakhar' - a flour prepared from seeds of Aesculus indica in remote areas of Himachal Pradesh India

Bacteriocin producing strain Brevibacillus laterosporus TK3, was isolated from 'Tatwakhar'- a flour prepared from seeds of Indian Horse Chestnut (Aesculus indica). Bacterial strain Brevibacillus laterosporus TK3 identified by morphological, biochemical techniques followed by 16S rRNA gene sequencing. The 16S rRNA sequence of bacteriocin producer was deposited in NCBI GenBank under accession no. KP861913.1. Bacteriocin of Brevibacillus laterosporus TK3 showed strong antagonistic activity against food spoiling/pathogenic bacteria viz. Listeria monocytogenes, Staphylococcus aureus and Clostridium perfringens. Bacteriocin production by Brevibacillus laterosporus TK3 was enhanced by optimizing production time, pH of the medium, inoculum size and incubation temperature. Maximum bacteriocin activity (6000 AU/ml) was recorded/obtained in basal salt medium of pH 5.5 with an inoculum size of 1.5 OD at 10% and incubation period of 24h at 35 °C. The bacteriocin was purified by single step gel exclusion chromatography. Molecular weight of active bacteriocin from Brevibacillus laterosporous TK3 was found to be 6 kDa according to SDS PAGE. The molecular mass of purified bacteriocin was confirmed as 5953.89 Da by MALDI TOF analysis. The purified bacteriocin was found desirable/suitable for food preservation as it showed wide spectrum of antimicrobial activity, resistance to high temperature, wide pH range and sensitivity to proteolytic enzymes thus, making it safe for human consumption.

Airway microbiome signature accurately discriminates Mycobacterium tuberculosis infection status

Mycobacterium tuberculosis remains one of the deadliest infectious agents globally. Amidst efforts to control TB, long treatment duration, drug toxicity, and resistance underscore the need for novel therapeutic strategies. Despite advances in understanding the interplay between microbiome and disease in humans, the specific role of the microbiome in predicting disease susceptibility and discriminating infection status in tuberculosis still needs to be fully investigated. We investigated the impact of M.tb infection and M.tb-specific IFNγ immune responses on airway microbiome diversity by performing TB GeneXpert and QuantiFERON-GOLD assays during the follow-up phase of a longitudinal HIV-Lung Microbiome cohort of individuals recruited from two large independent cohorts in rural Uganda. M.tb rather than IFNγ immune response mainly drove a significant reduction in airway microbiome diversity. A microbiome signature comprising Streptococcus, Neisseria, Fusobacterium, Prevotella, Schaalia, Actinomyces, Cutibacterium, Brevibacillus, Microbacterium, and Beijerinckiacea accurately discriminated active TB from Latent TB and M.tb-uninfected individuals.

Isolation, Characterization, Genome Annotation, and Evaluation of Hyaluronidase Inhibitory Activity in Secondary Metabolites of Brevibacillus sp. JNUCC 41: A Comprehensive Analysis through Molecular Docking and Molecular Dynamics Simulation

Brevibacillus sp. JNUCC 41, characterized as a plant-growth-promoting rhizobacterium (PGPR), actively participates in lipid metabolism and biocontrol based on gene analysis. This study aimed to investigate the crucial secondary metabolites in biological metabolism; fermentation, extraction, and isolation were performed, revealing that methyl indole-3-acetate showed the best hyaluronidase (HAase) inhibitory activity (IC50: 343.9 μM). Molecular docking results further revealed that the compound forms hydrogen bonds with the residues Tyr-75 and Tyr-247 of HAase (binding energy: -6.4 kcal/mol). Molecular dynamics (MD) simulations demonstrated that the compound predominantly binds to HAase via hydrogen bonding (MM-PBSA binding energy: -24.9 kcal/mol) and exhibits good stability. The residues Tyr-247 and Tyr-202, pivotal for binding in docking, were also confirmed via MD simulations. This study suggests that methyl indole-3-acetate holds potential applications in anti-inflammatory and anti-aging treatments.

New strain Brevibacillus laterosporus TSA31-5 produces both brevicidine and brevibacillin, exhibiting distinct antibacterial modes of action against Gram-negative and Gram-positive bacteria

The growing prevalence of antibiotic resistance has made it imperative to search for new antimicrobial compounds derived from natural products. In the present study, Brevibacillus laterosporus TSA31-5, isolated from red clay soil, was chosen as the subject for conducting additional antibacterial investigations. The fractions exhibiting the highest antibacterial activity (30% acetonitrile eluent from solid phase extraction) were purified through RP-HPLC. Notably, two compounds (A and B) displayed the most potent antibacterial activity against both Escherichia coli and Staphylococcus aureus. ESI-MS/MS spectroscopy and NMR analysis confirmed that compound A corresponds to brevicidine and compound B to brevibacillin. Particularly, brevicidine displayed notable antibacterial activity against Gram-negative bacteria, with a minimum inhibitory concentration (MIC) range of 1-8 μg/mL. On the other hand, brevibacillin exhibited robust antimicrobial effectiveness against both Gram-positive bacterial strains (MIC range of 2-4 μg/mL) and Gram-negative bacteria (MIC range of 4-64 μg/mL). Scanning electron microscopy analysis and fluorescence assays uncovered distinctive morphological alterations in bacterial cell membranes induced by brevicidine and brevibacillin. These observations imply distinct mechanisms of antibacterial activity exhibited by the peptides. Brevicidine exhibited no hemolysis or cytotoxicity up to 512 μg/mL, comparable to the negative control. This suggests its promising therapeutic potential in treating infectious diseases. Conversely, brevibacillin demonstrated elevated cytotoxicity in in vitro assays. Nonetheless, owing to its noteworthy antimicrobial activity against pathogenic bacteria, brevibacillin could still be explored as a promising antimicrobial agent.

Characterization of a Novel Antimicrobial Peptide Bacipeptin against Foodborne Pathogens

The increasing emergence of multidrug-resistant pathogens and development of biopreservatives in food industries has increased the demand of novel and safe antimicrobial agents. In this study, a marine bacterial strain Bacillus licheniformis M1 was isolated and exhibited obvious antimicrobial activities against foodborne pathogens, especially against methicillin-resistant Staphylococcus aureus. The antimicrobial agent was purified and identified as a novel antimicrobial peptide, which was designated as bacipeptin, and the corresponding mechanism was further investigated by electron microscopy observation and transcriptomic analysis with biochemical validation. The results showed that bacipeptin could reduce the virulence of methicillin-resistant Staphylococcus aureus and exerted its antimicrobial activity by interfering with histidine metabolism, inducing the accumulation of reactive oxygen species and down-regulating genes related to Na+/H+ antiporter and the cell wall, thus causing damage to the cell wall and membrane. Overall, our study provides a novel natural product against foodborne pathogens and discloses the corresponding action mechanism.

An insight into the utilization of microbial biosurfactants pertaining to their industrial applications in the food sector

Microbial biosurfactants surpass synthetic alternatives due to their biodegradability, minimal toxicity, selective properties, and efficacy across a wide range of environmental conditions. Owing to their remarkable advantages, biosurfactants employability as effective emulsifiers and stabilizers, antimicrobial and antioxidant attributes, rendering them for integration into food preservation, processing, formulations, and packaging. The biosurfactants can also be derived from various types of food wastes. Biosurfactants are harnessed across multiple sectors within the food industry, ranging from condiments (mayonnaise) to baked goods (bread, muffins, loaves, cookies, and dough), and extending into the dairy industry (cheese, yogurt, and fermented milk). Additionally, their impact reaches the beverage industry, poultry feed, seafood products like tuna, as well as meat processing and instant foods, collectively redefining each sector's landscape. This review thoroughly explores the multifaceted utilization of biosurfactants within the food industry as emulsifiers, antimicrobial, antiadhesive, antibiofilm agents, shelf-life enhancers, texture modifiers, and foaming agents.

Isolation and Characterization of Antimicrobial Peptides Isolated from Brevibacillus halotolerans 7WMA2 for the Activity Against Multidrug-Resistant Pathogens

Multidrug resistance to pathogens has posed a severe threat to public health. The threat could be addressed by antimicrobial peptides (AMPs) with broad-spectrum suppression. In this study, Brevibacillus halotolerans 7WMA2, isolated from marine sediment, produced AMPs against Gram-positive and Gram-negative bacteria. The AMPs were precipitated by ammonium sulfate 30% (w/v) from culture broth and dialyzed by a 1 kDa membrane. Tryptone Soy Agar (TSA) was used for the cultivation and resulted in the largest bacteria-inhibiting zones under aerobic conditions at 25 °C, 48 h. An SDS-PAGE gel overlay test revealed that strain 7WMA2 could produce AMPs of 5-10 kDa and showed no degradation when held at 121 °C for 30 min at a wide pH 2-12 range. The AMPs did not cause toxicity to HeLa cells with concentrations up to 500 µg/mL while increasing the arbitrary unit up to eight times. The study showed that the AMPs produced were unique, with broad-spectrum antimicrobial ability.

Anti-methicillin-resistant Staphylococcus aureus and antibiofilm activity of new peptides produced by a Brevibacillus strain

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is listed as a highly prioritized pathogen by the World Health Organization (WHO) to search for effective antimicrobial agents. Previously, we isolated a soil Brevibacillus sp. strain SPR19 from a botanical garden, which showed anti-MRSA activity. However, the active substances were still unknown.

Methods

The cell-free supernatant of this bacterium was subjected to salt precipitation, cation exchange, and reversed-phase chromatography. The antimicrobial activity of pure substances was determined by broth microdilution assay. The peptide sequences and secondary structures were characterized by tandem mass spectroscopy and circular dichroism (CD), respectively. The most active anti-MRSA peptide underwent a stability study, and its mechanism was determined through scanning electron microscopy, cell permeability assay, time-killing kinetics, and biofilm inhibition and eradication. Hemolysis was used to evaluate the peptide toxicity.

Results

The pure substances (BrSPR19-P1 to BrSPR19-P5) were identified as new peptides. Their minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) against S. aureus and MRSA isolates ranged from 2.00 to 32.00 and 2.00 to 64.00 µg/mL, respectively. The sequence analysis of anti-MRSA peptides revealed a length ranging from 12 to 16 residues accompanied by an amphipathic structure. The physicochemical properties of peptides were predicted such as pI (4.25 to 10.18), net charge at pH 7.4 (-3 to +4), and hydrophobicity (0.12 to 0.96). The CD spectra revealed that all peptides in the water mainly contained random coil structures. The increased proportion of α-helix structure was observed in P2-P5 when incubated with SDS. P2 (NH2-MFLVVKVLKYVV-COOH) showed the highest antimicrobial activity and high stability under stressed conditions such as temperatures up to 100 °C, solution of pH 3 to 10, and proteolytic enzymes. P2 disrupted the cell membrane and caused bacteriolysis, in which its action was dependent on the incubation time and peptide concentration. Antibiofilm activity of P2 was determined by which the half-maximal inhibition of biofilm formation was observed at 2.92 and 4.84 µg/mL for S. aureus TISTR 517 and MRSA isolate 2468, respectively. Biofilm eradication of tested pathogens was found at the P2 concentration of 128 µg/mL. Furthermore, P2 hemolytic activity was less than 10% at concentrations up to 64 µg/mL, which reflected the hemolysis index thresholds of 32.

Conclusion

Five novel anti-MRSA peptides were identified from SPR19. P2 was the most active peptide and was demonstrated to cause membrane disruption and cell lysis. The P2 activity was dependent on the peptide concentration and exposure time. This peptide had antibiofilm activity against tested pathogens and was compatible with human erythrocytes, supporting its potential use as an anti-MRSA agent in this post-antibiotic era.

Whole-genome analysis and secondary metabolites production of a new strain Brevibacillus halotolerans 7WMA2: A potential biocontrol agent against fungal pathogens

The extensive usage of synthetic fungicides against fungal diseases has caused adverse impacts on both human and agricultural crops. Therefore, the current study aims to establish a new bacterium 7WMA2, as a biocontrol agent to achieve better antifungal results. The strain 7WMA2 was isolated from marine sediment, displayed a broad spectrum of several fungi that includes Alternaria alternata, Cladosporium sp., Candida albicans, Fusarium oxysporum, Trichosporon pullulans, and Trichophyton rubrum. The 16S rRNA phylogeny inferred that strain 7WMA2 was a member of Brevibacillus. The phylogenetic and biochemical analyses revealed that the strain 7WMA2 belongs to the species of Brevibacillus halotolerans. The complete genome sequence of Brevibacillus halotolerans 7WMA2 consists of a circular chromosome of 5,351,077 bp length with a GC content of 41.39 mol %, including 4433 CDS, 111 tRNA genes, and 36 rRNA genes. The genomic analysis showed 23 putative biosynthetic secondary metabolite gene clusters responsible for non-ribosomal peptides, polyketides and siderophores. The antifungal compounds concentrated from cell-free fermentation broth demonstrated strong inhibition of fungi, and the compounds are considerably thermal stable and adaptable to pH range 2-12. This complete genome sequence has provided insight for further exploration of antagonistic ability and its secondary metabolite compounds indicated feasibility as biological control agents against fungal infections.

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.

Bovicin HC5 and nisin reduce cell viability and the thermal resistance of Alicyclobacillus acidoterrestris endospores in fruit juices

BACKGROUND

Alicyclobacillus acidoterrestris is an important thermoacidophilic spore-forming bacterium in fruit-juice deterioration, and alternative non-thermal methods have been investigated to control fruit juice spoilage. This work aimed to evaluate the capacity of bovicin HC5 and nisin to inhibit the growth of vegetative cells and reduce the thermal resistance of endospores of A. acidoterrestris inoculated (10⁷ CFU mL^-1 ) in different fruit juices. The number of viable cells was determined after 12 h incubation at 43 °C in the presence and absence of nisin or bovicin HC5 (10-100 AU mL^-1 ). The exposure time (min) required to kill 90% of the initial population (reduction of one log factor) at 90 ºC (D_90ºC ) was used to assess the thermal resistance of A. acidoterrestris endospores exposed (80 AU mL^-1 ) or non-exposed to the bacteriocins. Additionally, the effect of bovicin and nisin on the morphology and cell structure of A. acidoterrestris was evaluated by atomic force microscopy (AFM).

RESULTS

Bovicin HC5 and nisin were bactericidal against A. acidoterrestris inoculated in fruit juices and reduced the D_90°C values up to 30-fold. AFM topographical images revealed substantial structural changes in the cellular framework of vegetative cells upon treatment with bovicin HC5 or nisin.

CONCLUSIONS

These results emphasize the potential application of lantibiotics as additional hurdles in food processing to control thermoacidophilic spoilage bacteria in fruit juices. © 2022 Society of Chemical Industry.

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.

Identification and Characterization of a Potential Antimicrobial Peptide Isolated from Soil Brevibacillus sp. WUL10 and Its Activity against MRSA Pathogens

Methicillin-resistant Staphylococcus aureus (MRSA) is a severe threat to public health globally. The development of novel agents has encountered the repeated mechanism of drug resistance. This study aimed to investigate an anti-MRSA substance isolated from a promising soil bacterium. The result showed that an isolate (WUL10) was in the Brevibacillus genus. The minimum inhibitory concentration (MIC) of the purified substance was 1 µg/mL against S. aureus TISTR 517 and MRSA strains. This substance showed the bactericidal effect at the concentration of 1–2 µg/mL against these bacterial indicators. The activity of the substance retained more than 95% when encountering high temperatures and a wide range of pH, but it was sensitive to proteolytic enzymes and SDS. It was identified as a novel antimicrobial peptide (KVLVKYLGGLLKLAALMV-COOH) with the predicted structure of α-helix. The substance could rupture the cell wall of the tested pathogen. MIC and MBC of the synthesized peptide were 16 and 64 µg/mL, respectively. The difference in the activity between the isolated and synthetic peptides might be from the synergistic effects of other AMPs in the purified substance. This novel AMP would provide an advantage for further development of anti-MRSA substances to manage the situation of antibiotic resistance.

Comprehensive Review on Applications of Surfactants in Vaccine Formulation, Therapeutic and Cosmetic Pharmacy and Prevention of Pulmonary Failure due to COVID-19

Our world is under serious threat of environmental degradation, climate change and in association with this the out breaks of diseases as pandemics. The devastating impact of the very recent COVID-19, The sharp increase in cases of Cancer, Pulmonary failure, Heart health has triggered questions for the sustainable development of pharmaceutical and medical sciences. In the search of inclusive and effective strategies to meet today’s demand, improvised methodologies and alternative green chemical, bio-based precursors are being introduced by scientists around the globe. In this extensive review we have presented the potentiality and Realtime applications of both synthetic and bio-based surfactants in bio-medical and pharmaceutical fields. For their excellent unique amphoteric nature and ability to solubilise in both organic and inorganic drugs, surfactants are one of the most potential candidates for bio-medicinal fields such as dermatology, drug delivery, anticancer treatment, surfactant therapy, vaccine formulation, personal hygiene care and many more. The self-assembly property of surfactants is a very powerful function for drug delivery systems that increases the bio-availability of the poorly aqueous soluble pharmaceutical products by influencing their solubility. Over the decades many researchers have reported the antimicrobial, anti-adhesive, antibiofilm, anti-inflammatory, antioxidant activities of surfactants regarding its utility in medicinal purposes. In some reports surfactants are found to have spermicidal and laxative activity too. This comprehensive report is targeted to enlighten the versatile applications of Surfactants in drug delivery, vaccine formulation, Cancer Treatment, Therapeutic and cosmetic Pharmaceutical Sciences and prevention of pulmonary failure due to COVID-19.

Purification and characterization of antibacterial surfactin isoforms produced by Bacillus velezensis SK

Bacillus velezensis SK having broad-spectrum antimicrobial activity has been isolated from soil. The efficient extraction of antimicrobial compounds produced in various mediums has been done using Diaion HP-20 resin. Further, characterization of an antimicrobial compound by TLC, FTIR, in-situ bioautography analysis revealed the presence of cyclic lipopeptides, which is then purified by the combination of silica gel, size exclusion, dual gradient, and RP-HPLC chromatography techniques. Growth kinetic studies showed that Bacillus velezensis SK produces a mixture of lipopeptides (1.33 gL^-1). The lipopeptide exhibits good pH (2-10) and temperature stability up to 80 °C. LC-ESI-MS analysis of partially purified lipopeptide identified variant of surfactin, further analysis of purified chromatographic fractions revealed the occurrence of most abundant C₁₅-surfactin homologues (m/z 1036.72 Da). The isolated surfactin exhibits good antimicrobial activity (1600 AU/ml) against drug-resistant food-born B. cereus and human pathogen Staphylococcus aureus. Hence, identified strain B. velezensis SK and its potent antibacterial surfactin lipopeptide could be used in various food and biomedical applications.

Simultaneous Production of Antibacterial Protein and Lipopeptides in Bacillus tequilensis, Detected by MALDI-TOF and GC Mass Analyses

As antibiotic resistance is nowadays one of the important challenges, efforts are crucial for the discovery of novel antibacterial drugs. This study aimed to evaluate antimicrobial/anticancerous activities of halophilic bacilli from the human microbiota. A spore-forming halotolerant bacterium with antibacterial effect against Staphylococcus aureus was isolated from healthy human feces. The antibacterial protein components of the extracted supernatant were identified by SDS-PAGE and zymography. The MALDI-TOF, GC mass, and FTIR analyses were used for peptide and lipopeptide identification, respectively. The stability, toxicity, and anticancerous effects were investigated using MTT and Flow cytometry methods. According to the molecular analysis, the strain was identified as Bacillus tequilensis and showed potential probiotic properties, such as bile and acid resistance, as well as eukaryotic cell uptake. SDS-PAGE and zymography showed that 15 and 10-kDa fragments had antibacterial effects. The MALDI-TOF mass analysis indicated that the 15-kDa fragment was L1 ribosomal protein, which was the first report of the RpL1 in bacilli. GC-mass and FTIR analyses confirmed the lipopeptide nature of the 10-kDa fragment. Both the extracted fractions (precipitation or "P" and chloroform or "C" fractions) were stable at < 100 °C for 10 min, and their antibacterial effects were preserved for more than 6 months. Despite its non-toxicity, the P fraction had anticancer activities against MCF7 cells. The anticancer and antibacterial properties of B. tequilensis, along with its non-toxicity and stability, have made it a potential candidate for studying the beneficial probiotic properties for humans and drug production.

Venom peptides - A comprehensive translational perspective in pain management

Venom peptides have been evolving complex therapeutic interventions that potently and selectively modulate a range of targets such as ion channels, receptors, and signaling pathways of physiological processes making it potential therapeutic. Several venom peptides were deduced in vivo for clinical development targeting pain management, diabetes, cardiovascular diseases, antimicrobial activity. Several contributions have been detailed for a clear perspective for a better understanding of venomous animals, their venom, and their pharmacological effects. Here we unravel and summarize the recent advances in wide venom peptides across varieties of species for their therapeutics prospects.

Deciphering the Antibacterial Role of Peptide From Bacillus subtilis subsp. spizizenii Ba49 Against Staphylococcus aureus

An increase in antibiotic resistance has led to escalating the need for the development of alternate therapy. Antimicrobial peptides (AMPs) are at the forefront of replacing conventional antibiotics, showing slower development of drug resistance, antibiofilm activity, and the ability to modulate the host immune response. The ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens that jeopardize most conventional antibiotics are known to be involved in severe respiratory tract, bloodstream, urinary tract, soft tissue, and skin infections. Among them, S. aureus is an insidious microbe and developed resistance against conventional antibiotics. In the present study, an AMP (named as peptide-Ba49) isolated from Bacillus subtilis subsp. spizizenii strain from Allium cepa (the common onion) exhibited strong antibacterial efficacy against S. aureus ATCC 25923. The mode of action of this peptide-Ba49 on S. aureus was deciphered through various sensitive probes, i.e., DiSC₃ (5) and H₂DCFDA, suggesting the peptide-Ba49 to be acting upon through change in membrane potential and by triggering the production of reactive oxygen species (ROS). This induced disruption of the cell membrane was further supported by morphological studies using scanning electron microscopy (SEM). Investigations on a possible post-antibiotic effect (PAE) of peptide-Ba49 showed prolonged PAE against S. aureus. Furthermore, the peptide-Ba49 prevented the formation of S. aureus biofilm at low concentration and showed its potential to degrade the mature biofilm of S. aureus. The peptide-Ba49 also exhibited intracellular killing potential against S. aureus ATCC 25923 in the macrophage cells, and moreover, peptide-Ba49 was found to bolster the fibroblast cell migration in the scratch assay at low concentration, exhibiting a wound healing efficacy of this peptide. These studies demonstrated that peptide-Ba49 isolated from the strain B. subtilis subsp. spizizenii could be a therapeutic candidate to combat the pathogenic S. aureus infections.

Brevibacillin 2V Exerts Its Bactericidal Activity via Binding to Lipid II and Permeabilizing Cellular Membranes

Lipo-tridecapeptides, a class of bacterial non-ribosomally produced peptides, show strong antimicrobial activity against Gram-positive pathogens, including antibiotic-resistant Staphylococcus aureus and Enterococcus spp. However, many of these lipo-tridecapeptides have shown high hemolytic activity and cytotoxicity, which has limited their potential to be developed into antibiotics. Recently, we reported a novel antimicrobial lipo-tridecapeptide, brevibacillin 2V, which showed no hemolytic activity against human red blood cells at a high concentration of 128 mg/L, opposite to other brevibacillins and lipo-tridecapeptides. In addition, brevibacillin 2V showed much lower cytotoxicity than the other members of the brevibacillin family. In this study, we set out to elucidate the antimicrobial mode of action of brevibacillin 2V. The results show that brevibacillin 2V acts as bactericidal antimicrobial agent against S. aureus (MRSA). Further studies show that brevibacillin 2V exerts its bactericidal activity by binding to the bacterial cell wall synthesis precursor Lipid II and permeabilizing the bacterial membrane. Combined solid-state NMR, circular dichroism, and isothermal titration calorimetry assays indicate that brevibacillin 2V binds to the GlcNAc-MurNAc moiety and/or the pentapeptide of Lipid II. This study provides an insight into the antimicrobial mode of action of brevibacillin 2V. As brevibacillin 2V is a novel and promising antibiotic candidate with low hemolytic activity and cytotoxicity, the here-elucidated mode of action will help further studies to develop it as an alternative antimicrobial agent.

The determination of antibacterial mode for cationic lipopeptides brevibacillins against Salmonella typhimurium by quantum chemistry calculation

Brevibacillins are broad-spectrum cationic antimicrobial lipopeptides produced by Brevibacillus laterosporus fmb70 CGMCC 18426. The antibacterial mode of brevibacillins against Salmonella typhimurium CICC 21493 was investigated by quantum chemistry calculation in this study. The addition of LPS, Mg²⁺, and Ca²⁺ partially reduced the antimicrobial activity of brevibacillin and brevibacillin V against S. typhimurium, which indicated that the two cationic lipopeptides could bind to LPS and displaced the divalent cations on the LPS network. Release of LPS from S. typhimurium by brevibacillin and brevibacillin V resulted in destroying the dense LPS network and increasing the permeability of the outer membrane. Quantum chemistry calculation analysis revealed that Lys7 is the most critical amino acid residue to destroy the outer membrane. The total average N-H charge difference of the three protonated amino groups (Orn3-NH₃, Lys7-NH₃, and Lys10-NH₃) determined the ability of brevibacillin V to bind LPS stronger than brevibacillin. Calcein complete leakage from liposomes and release of DiSC₃-5 from the cytoplasmic membrane (CM) indicated that brevibacillin and brevibacillin V may destroy the CM. Brevibacillin and brevibacillin V exhibited their antimicrobial activities through membrane damages, where the OM permeability with high concentration of 64-256 µg/mL and membrane damage of CM with a low concentration of 4 μg/mL. Our finding might be helpful to understand the broad-spectrum antimicrobial mechanism of cationic lipopeptide and to design the novel antimicrobial peptide. KEY POINTS: • Brevibacillin V had stronger affinity for LPS than brevibacillin. • The N-H charge difference was the key of the difference in the affinity to LPS. • Brevibacillins inhibited Salmonella by displacing the divalent cations on the LPS.

Brevibacillin 2V, a Novel Antimicrobial Lipopeptide With an Exceptionally Low Hemolytic Activity

Bacterial non-ribosomally produced peptides (NRPs) form a rich source of antibiotics, including more than 20 of these antibiotics that are used in the clinic, such as penicillin G, colistin, vancomycin, and chloramphenicol. Here we report the identification, purification, and characterization of a novel NRP, i.e., brevibacillin 2V (lipo-tridecapeptide), from Brevibacillus laterosporus DSM 25. Brevibacillin 2V has a strong antimicrobial activity against Gram-positive bacterial pathogens (minimum inhibitory concentration = 2 mg/L), including difficult-to-treat antibiotic-resistant Enterococcus faecium, Enterococcus faecalis, and Staphylococcus aureus. Notably, brevibacillin 2V has a much lower hemolytic activity (HC₅₀ > 128 mg/L) and cytotoxicity (CC₅₀ = 45.49 ± 0.24 mg/L) to eukaryotic cells than previously reported NRPs of the lipo-tridecapeptide family, including other brevibacillins, which makes it a promising candidate for antibiotic development. In addition, our results demonstrate that brevibacillins display a synergistic action with established antibiotics against Gram-negative bacterial pathogens. Probably due to the presence of non-canonical amino acids and D-amino acids, brevibacillin 2V showed good stability in human plasma. Thus, we identified and characterized a novel and promising antimicrobial candidate (brevibacillin 2V) with low hemolytic activity and cytotoxicity, which can be used either on its own or as a template for further total synthesis and modification.

Recent Advances in Biomedical, Therapeutic and Pharmaceutical Applications of Microbial Surfactants

The spread of antimicrobial-resistant pathogens typically existing in biofilm formation and the recent COVID-19 pandemic, although unrelated phenomena, have demonstrated the urgent need for methods to combat such increasing threats. New avenues of research for natural molecules with desirable properties to alleviate this situation have, therefore, been expanding. Biosurfactants comprise a group of unique and varied amphiphilic molecules of microbial origin capable of interacting with lipidic membranes/components of microorganisms and altering their physicochemical properties. These features have encouraged closer investigations of these microbial metabolites as new pharmaceutics with potential applications in clinical, hygiene and therapeutic fields. Mounting evidence has indicated that biosurfactants have antimicrobial, antibiofilm, antiviral, immunomodulatory and antiproliferative activities that are exploitable in new anticancer treatments and wound healing applications. Some biosurfactants have already been approved for use in clinical, food and environmental fields, while others are currently under investigation and development as antimicrobials or adjuvants to antibiotics for microbial suppression and biofilm eradication strategies. Moreover, due to the COVID-19 pandemic, biosurfactants are now being explored as an alternative to current products or procedures for effective cleaning and handwash formulations, antiviral plastic and fabric surface coating agents for shields and masks. In addition, biosurfactants have shown promise as drug delivery systems and in the medicinal relief of symptoms associated with SARS-CoV-2 acute respiratory distress syndrome.

Promising Anti-MRSA Activity of Brevibacillus sp. Isolated from Soil and Strain Improvement by UV Mutagenesis

Antibiotic-resistant infection is a major health problem, and a limited number of drugs are currently approved as antibiotics. Soil bacteria are promising sources in the search for novel antibiotics. The aim of the present study is to isolate and assess soil bacteria with anti-MRSA activity and improve their capabilities by UV mutagenesis. Soil samples from the upper south of Thailand were screened for antibacterial activity using the cross-streak method. Agar well diffusion was used to examine the activity of isolates against a spectrum of human pathogens. The most active isolate was identified by 16S rRNA sequencing, and the production kinetics and stability were investigated. The most promising isolate was mutated by UV radiation, and the resulting activity and strain stability were studied. The results show that isolates from the cross-streak method could inhibit Staphylococcus aureus TISTR 517 (94 isolates) and Escherichia coli TISTR 887 (67 isolates). Nine isolates remained active against S. aureus TISTR 517 and MRSA, and eight isolates inhibited the growth of E. coli TISTR 887 as assessed using agar well diffusion. The most active strain was Brevibacillus sp. SPR-20, which had the highest activity at 24 h of incubation. The active substances in culture supernatants exhibited more than 90% activity when subjected to treatments involving various heat, enzymes, surfactants, and pH conditions. The mutant M201 showed significantly higher activity (109.88–120.22%) and strain stability compared to the wild-type strain. In conclusion, we demonstrate that soil Brevibacillus sp. is a potential resource that can be subjected to UV mutagenesis as a useful approach for improving the production of anti-MRSA in the era of antibiotic resistance.

Novel Modifications of Nonribosomal Peptides from Brevibacillus laterosporus MG64 and Investigation of Their Mode of Action

Nonribosomal peptides (NRPs) are a class of secondary metabolites usually produced by microorganisms. They are of paramount importance in different applications, including biocontrol and pharmacy. Brevibacillus spp. are a rich source of NRPs yet have received little attention. In this study, we characterize four novel bogorol variants (bogorols I to L, cationic linear lipopeptides) and four succilins (succilins I to L, containing a succinyl group that is attached to the Orn₃/Lys₃ in bogorols I to L) from the biocontrol strain Brevibacillus laterosporus MG64. Further investigation revealed that the bogorol family of peptides employs an adenylation pathway for lipoinitiation, different from the usual pattern, which is based on an external ligase and coenzyme A. Moreover, the formation of valinol was proven to be mediated by a terminal reductase domain and a reductase encoded by the bogI gene. Furthermore, succinylation, which is a novel type of modification in the family of bogorols, was discovered. Its occurrence requires a high concentration of the substrate (bogorols), but its responsible enzyme remains unknown. Bogorols display potent activity against both Gram-positive and Gram-negative bacteria. Investigation of their mode of action reveals that bogorols form pores in the cell membrane of both Gram-positive and Gram-negative bacteria. The combination of bogorols and relacidines, another class of NRPs produced by B. laterosporus MG64, displays a synergistic effect on different pathogens, suggesting the great potential of both peptides as well as their producer B. laterosporus MG64 for broad applications. Our study provides a further understanding of the bogorol family of peptides as well as their applications.IMPORTANCE NRPs form a class of secondary metabolites with biocontrol and pharmaceutical potential. This work describes the identification of novel bogorol variants and succinylated bogorols (namely, succilins) and further investigates their biosynthetic pathway and mode of action. Adenylation domain-mediated lipoinitiation of bogorols represents a novel pathway by which NRPs incorporate fatty acid tails. This pathway provides the possibility to engineer the lipid tail of NRPs without identifying a fatty acid coenzyme ligase, which is usually not present in the biosynthetic gene cluster. The terminal reductase domain (TD) and BogI-mediated valinol formation and their effect on the biological activity of bogorols are revealed. Succinylation, which is rarely reported in NRPs, was discovered in the bogorol family of peptides. We demonstrate that bogorols combat bacterial pathogens by forming pores in the cell membrane. We also report the synergistic effect of two natural products (relacidine B and bogorol K) produced by the same strain, which is relevant for competition for a niche.

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.

Phenolic Content and Antimicrobial and Anti-Inflammatory Effects of Solidago virga-aurea, Phyllanthus niruri, Epilobium angustifolium, Peumus boldus, and Ononis spinosa Extracts

Prostatitis is an inflammatory condition that is related to multiple infectious agents, including bacteria and fungi. Traditional herbal extracts proved efficacious in controlling clinical symptoms associated with prostatitis. In this context, the aim of the present study was to explore the efficacy of extracts from Solidago virga-aurea, Ononis spinosa, Peumus boldus, Epilobium angustifolium, and Phyllanthus niruri against bacterial (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus cereus) and fungi strains (Candida albicans; C. tropicalis) involved in prostatitis. Additionally, anti-mycotic effects were tested against multiple species of dermatophytes (Trichophyton rubrum, T. tonsurans, T. erinacei, Arthroderma crocatum, A. quadrifidum, A. gypseum, A. currey, and A. insingulare). Antioxidant effects were also evaluated in isolated rat prostates challenged with lipopolysaccharide (LPS), and phytochemical analyses were conducted to identify and quantify selected phenolic compounds, in the extracts. Finally, a bioinformatics analysis was conducted to predict putative human and microbial enzymes targeted by extracts’ phytocompounds and underlying the observed bio-pharmacological effects. The phytochemical analysis highlighted that rutin levels could be crucial for explaining the highest antibacterial activity of P. boldus extract, especially against E. coli and B. cereus. On the other hand, in the E. angustifolium extract, catechin concentration could partially explain the highest efficacy of this extract in reducing lipid peroxidation, in isolated rat prostates stimulated with LPS. Concluding, the results of the present study showed moderate antimicrobial and anti-inflammatory effects induced by water extracts of S. virga-aurea, P. boldus, E. angustifolium, P. niruri, and O. spinosa that could be related, at least partially, to the phenolic composition of the phytocomplex.

Controlling foodborne pathogens with natural antimicrobials by biological control and antivirulence strategies

Foodborne diseases represent a global health threat besides the great economic losses encountered by the food industry. These hazards necessitate the implementation of food preservation methods to control foodborne pathogens, the causal agents of human illnesses. Until now, most control methods rely on inhibiting the microbial growth or eliminating the pathogens by applying lethal treatments. Natural antimicrobials, which inhibit microbial growth, include traditional chemicals, naturally occurring antimicrobials, or biological preservation (e.g. beneficial microbes, bacteriocins, or bacteriophages). Although having great antimicrobial effectiveness, challenges due to the adaptation of foodborne pathogens to such control methods are becoming apparent. Such adaptation enables the survival of the pathogens in foods or food-contact environments. This imperative concern inspires contemporary research and food industry sector to develop technologies which do not target microbial growth but disarming microbial virulence factors. These technologies, referred to as "antivirulence", render the microbe non-capable of causing the disease with very limited or no opportunities for the pathogenic microorganisms to develop resistance. For the sake of safer and fresh-like foods, with no effect on the sensory properties of foods, a combination of two or more natural antimicrobials or with other stressors, is now widespread, to preserve foods. This review introduces and critically describes the traditional versus the emerging uses of natural antimicrobials for controlling foodborne pathogens in foods. Development of biological control strategies using natural antimicrobials proved to be effective in inhibiting microbial growth in foods and allowing improved food safety. In the meanwhile, discovery of new antivirulence agents could be a transformative strategy in food preservation in the far future.

Genome-Guided Mass Spectrometry Expedited the Discovery of Paraplantaricin TC318, a Lantibiotic Produced by Lactobacillus paraplantarum Strain Isolated From Cheese

The quest for potent alternatives to the currently used antimicrobials is urged by health professionals, considering the rapid rise in resistance to preservatives and antibiotics among pathogens. The current study was initiated to search for novel and effective bacteriocins from food microbes, preferably lactic acid bacteria (LAB), for potential use as preservatives. Advances in genome-guided mass spectrometry (MS) were implemented to expedite identifying and elucidating the structure of the recovered antimicrobial agent. A LAB strain, OSY-TC318, was isolated from a Turkish cheese, and the crude extract of the cultured strain inhibited the growth of various pathogenic and spoilage bacteria such as Bacillus cereus, Clostridium sporogenes, Enterococcus faecalis, Listeria monocytogenes, Salmonella enterica ser. Typhimurium, and Staphylococcus aureus. The antimicrobial producer was identified as Lactobacillus paraplantarum using MS biotyping and genomic analysis. Additionally, L. paraplantarum OSY-TC318 was distinguished from closely related strains using comparative genomic analysis. Based on in silico analysis, the genome of the new strain contained a complete lantibiotic biosynthetic gene cluster, encoding a novel lantibiotic that was designated as paraplantaricin TC318. The bioinformatic analysis of the gene cluster led to the prediction of the biosynthetic pathway, amino acid sequence, and theoretical molecular mass of paraplantaricin TC318. To verify the genomic analysis predictions, paraplantaricin TC318 was purified from the producer cellular crude extract using liquid chromatography, followed by structural elucidation using Fourier transform ion cyclotron resonance MS analysis. This genome-guided MS analysis revealed that the molecular mass of paraplantaricin TC318 is 2,263.900 Da, its chemical formula is C₁₀₆H₁₃₃N₂₇O₂₂S₄, and its primary sequence is F-K-S-W-S-L-C-T-F-G-C-G-H-T-G-S-F-N-S-F-C-C. This lantibiotic, which differs from mutacin 1140 at positions 9, 12, 13, and 20, is considered a new member of the epidermin group in class I lantibiotics. In conclusion, the study revealed a new L. paraplantarum strain producing a novel lantibiotic that is potentially useful in food and medical applications.

Diversity, Chemical Constituents and Biological Activities of Endophytic Fungi Isolated from Schinus terebinthifolius Raddi

Schinus terebinthifolius Raddi is a medicinal plant widely used for the treatment of various diseases. The secondary metabolites responsible for the pharmacological properties can be produced directly by the plant or by endophytic fungi. The objective of this study was to evaluate the diversity of endophytic fungi of different parts of S. terebinthifolius and to identify chemical compounds produced by endophytes and their antioxidant and antibacterial activities. For this, fruits, stem bark and roots were dried, ground and placed in fungal growth medium. The selected endophytes were grown and subjected to extraction with ethyl acetate. DPPH, FRAP, β-carotene bleaching and antimicrobial assays were performed. The phylogenetic tree was elaborated, encompassing 15 different species. The fungal extracts showed hydroxybenzoic acids and 1-dodecanol as predominant compounds. All fungal extracts exhibited antioxidant activity. The fungal extracts exhibited bactericidal and bacteriostatic activities against Gram-positive and Gram-negative bacterial ATCC strains and against methicillin-resistant nosocomial bacteria. Among the 10 endophytic fungi evaluated, the extract of the fungus Ochrocladosporium elatum showed higher phenolic content and exhibited higher antioxidant and antibacterial activities in all tests. Together, the results increase the known diversity of S. terebinthifolius endophytic fungi, secondary metabolites produced and their antioxidant and antibacterial activities.

Characterization of plant growth-promoting rhizobacteria from perennial ryegrass and genome mining of novel antimicrobial gene clusters

Background

Plant growth-promoting rhizobacteria (PGPR) are good alternatives for chemical fertilizers and pesticides, which cause severe environmental problems worldwide. Even though many studies focus on PGPR, most of them are limited in plant-microbe interaction studies and neglect the pathogens affecting ruminants that consume plants. In this study, we expand the view to the food chain of grass-ruminant-human. We aimed to find biocontrol strains that can antagonize grass pathogens and mammalian pathogens originated from grass, thus protecting this food chain. Furthermore, we deeply mined into bacterial genomes for novel biosynthetic gene clusters (BGCs) that can contribute to biocontrol.

Results

We screened 90 bacterial strains from the rhizosphere of healthy Dutch perennial ryegrass and characterized seven strains (B. subtilis subsp. subtilis MG27, B. velezensis MG33 and MG43, B. pumilus MG52 and MG84, B. altitudinis MG75, and B. laterosporus MG64) that showed a stimulatory effect on grass growth and pathogen antagonism on both phytopathogens and mammalian pathogens. Genome-mining of the seven strains discovered abundant BGCs, with some known, but also several potential novel ones. Further analysis revealed potential intact and novel BGCs, including two NRPSs, four NRPS-PKS hybrids, and five bacteriocins.

Conclusion

Abundant potential novel BGCs were discovered in functional protective isolates, especially in B. pumilus, B. altitudinis and Brevibacillus strains, indicating their great potential for the production of novel secondary metabolites. Our report serves as a basis to further identify and characterize these compounds and study their antagonistic effects against plant and mammalian pathogens.

Isolation, characterization and application of a polyvalent phage capable of controlling Salmonella and Escherichia coli O157:H7 in different food matrices

Salmonella Enteritidis, Salmonella Typhimurium, and Escherichia coli O157:H7 are the most important foodborne pathogens, causing serious food poisoning outbreaks worldwide. Bacteriophages are increasingly considered as novel antibacterial agents to control foodborne pathogens. In this study, 8 Salmonella phages and 10 E. coli O157:H7 phages were isolated from chicken products. A polyvalent phage PS5 capable of infecting S. Enteritidis, S. Typhimurium, and E. coli O157:H7 was further characterized and its efficacy in reducing these foodborne pathogens was evaluated in in vitro and in foods. Morphology, one-step growth, and stability assay showed that phage PS5 was a myovirus, with relatively short latent periods, large burst sizes, and high stability. Genome sequencing analysis revealed that the genome of PS5 does not contain any genes associated to antibiotic resistance, toxins, lysogeny, and virulence factors. In broth, phage PS5 significantly decreased the viable counts of all the three bacterial hosts by more than 1.3 log CFU/mL compared to controls after 2 h of incubation at 4 °C and 24 °C. In foods, treatment with PS5 also resulted in significant reductions of viable counts of all the three bacterial hosts compared to controls at temperatures tested. This is the first report on single phage capable of simultaneously controlling S. Enteritidis, S. Typhimurium and E. coli O157:H7 in both in vitro and in foods.

Discovery of a Novel Antimicrobial Lipopeptide, Brevibacillin V, from Brevibacillus laterosporus fmb70 and Its Application on the Preservation of Skim Milk

Increasing cases of infections by foodborne pathogenic bacteria resulted in a great demand to find safe and novel antimicrobial compounds that can be used in the food industry. The isolation and application of antimicrobial peptides including lipopeptides has been increasing tremendously in the past years. In this study, a new bacterial strain called Brevibacillus laterosporus fmb70 (fmb70) was isolated and exhibited strong antimicrobial activities against Gram-positive, Gram-negative bacteria, and fungi. Two major antimicrobial components produced by fmb70 were respectively identified as lipopeptide: brevibacillin V (MW: 1570.12 Da) and brevibacillin (MW: 1583.75 Da), of which brevibacillin V was a new compound. Both of them consisted of 13 amino acids and C₆ fatty acyl (FA) chain. Brevibacillin V and brevibacillin showed significant antimicrobial activities against most foodborne pathogenic bacteria and phytopathogenic fungi. They stayed activity at 100 °C and remained 50% of their antimicrobial activities at pH 3 for 22 h. Hemolytic activities of them were lower than 8%. They effectively eliminated the S. aureus GIM 1.142 and L. monocytogenes ATCC 21633 in skim milk. In conclusion, the Brevibacillus laterosporus fmb70 and its major antimicrobial components has remarkable potentials in the food industry.

Cold-adapted bacterial extracts as a source of anti-infective and antimicrobial compounds against Staphylococcus aureus

Aim: The dramatic emergence of antibiotic resistance has directed the interest of research toward the discovery of novel antimicrobial molecules. In this context, cold-adapted marine bacteria living in polar regions represent an untapped reservoir of biodiversity endowed with an interesting chemical repertoire. The aim of this work was to identify new antimicrobials and/or antibiofilm molecules produced by cold-adapted bacteria. Materials & methods: Organic extracts obtained from polar marine bacteria were tested against Staphylococcus aureus. Most promising samples were subjected to suitable purification strategies. Results: Results obtained led to the identification of a novel lipopeptide able to effectively inhibit the biofilm formation of S. aureus. Conclusion: New lipopeptide may be potentially useful in a wide variety of biotechnological and medical applications.

Phylogenetic determinants of toxin gene distribution in genomes of Brevibacillus laterosporus

Brevibacillus laterosporus is a globally ubiquitous, spore forming bacterium, strains of which have shown toxic activity against invertebrates and microbes and several have been patented due to their commercial potential. Relatively little is known about this bacterium. Here, we examined the genomes of six published and five newly determined genomes of B. laterosporus, with an emphasis on the relationships between known and putative toxin encoding genes, as well as the phylogenetic relationships between strains. Phylogenetically, strain relationships are similar using average nucleotide identity (ANI) values and multi-gene approaches, although PacBio sequencing revealed multiple copies of the 16S rDNA gene which lessened utility at the strain level. Based on ANI values, the New Zealand isolates were distant from other isolates and may represent a new species. While all of the genomes examined shared some putative toxicity or virulence related proteins, many specific genes were only present in a subset of strains.

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We examined genomes of 11 Brevibacillus laterosporus, a bacterium which is antagonistic to invertebrates and/or microbes

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Multiple phylogenetic methods showed New Zealand isolates more distant than all other isolates

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Each genome could contain 11–13 copies of the 16S rDNA gene, some of which were not identical

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Many putative toxin encoding genes were present in the genomes, but the toxin complement varied from isolate to isolate

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Variation in occurrence of toxin-encoding genes indicates the potential to find strains with new combinations of activities

Brevibacillus laterosporus strains BGSP7, BGSP9 and BGSP11 isolated from silage produce broad spectrum multi-antimicrobials

Bacteria active against multi-drug resistant pathogens, isolated by direct selection of colonies from clover silage samples, produce zones of inhibition against two Gram-negative (Klebsiella pneumoniae Ni9 and Pseudomonas aeruginosa MMA83) and two Gram-positive (Staphylococcus aureus ATCC25923 and Listeria monocytogenes ATCC19111) pathogens. Isolates BGSP7, BGSP9, BGSP11 and BGSP12 produced the largest zones of inhibition against all four pathogens when grown in LB broth with aeration at 37°C. Isolates BGSP7, BGSP9, BGSP11 and BGSP12 were identified as Brevibacillus laterosporus and pulsed field gel electrophoresis and extracellular protein profiles showed that three different strains (BGSP7, BGSP9 and BGSP11) were isolated. A semi-native SDS-PAGE (sodium dodecyl sulphate-polyacrylamide gel electrophoresis) gel overlay assay showed that BGSP7 and BGSP9 produce small antimicrobial molecules of about 1.5 kDa, while BGSP11 produces antimicrobial molecules of 1.5 and 6 kDa active against S. aureus ATCC25923. Amino acid analysis of two antimicrobial molecules (1583.73 Da; from BGSP7 and 1556.31 Da; from BGSP11) revealed that they have a similar composition and differ only by virtue of the presence of a methionine which is present only in BGSP11 molecule. Genome sequencing of the three isolates revealed the presence of gene clusters associated with the production of non-ribosomally synthesized peptides (brevibacillin, bogorol, gramicidin S, plipastatin and tyrocin) and bacteriocins (laterosporulin, a lactococcin 972-like bacteriocin, as well as putative linocin M18, sactipeptide, UviB and lantipeptide-like molecules). Ultimately, the purification of a number of antimicrobial molecules from each isolate suggests that they can be considered as potent biocontrol strains that produce an arsenal of antimicrobial molecules active against Gram-positive and Gram-negative multi-resistant pathogens, fungi and insects.

Novel linear lipopeptide paenipeptin C' binds to lipopolysaccharides and lipoteichoic acid and exerts bactericidal activity by the disruption of cytoplasmic membrane

BACKGROUND

There is an urgent need to develop potent antimicrobials for the treatment of infections caused by antibiotic-resistant bacterial pathogens. Paenipeptin C' (C8-Pat) is a novel linear lipopeptide recently discovered by our group. The objectives of this study were to determine the time-kill kinetics of paenipeptin C' against Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213 and to investigate its mechanism of action.

RESULTS

Paenipeptin C' was synthesized by solid-phase peptide synthesis and purified by HPLC to homogeneity. Paenipeptin C' showed concentration-dependent bactericidal activity against P. aeruginosa and S. aureus. Purified lipopolysaccharides (LPS) from the outer membrane of Gram-negative bacteria and lipoteichoic acid (LTA) from Gram-positive bacteria significantly decreased the antibacterial activity of paenipeptin C', which indicated that LPS and LTA on cell surfaces are likely the initial binding targets of this antibiotic agent. Moreover, paenipeptin C' damaged bacterial cytoplasmic membranes, as evidenced by the depolarization of membrane potential and leakage of intracellular potassium ions. Specifically, paenipeptin C' at 32-64 μg/mL caused a significant membrane potential depolarization in P. aeruginosa and S. aureus. This antibiotic at 64-128 μg/mL rapidly induced the release of intracellular potassium ions from P. aeruginosa and S. aureus. Transmission electron microscopy imaging results showed that paenipeptin C' at bactericidal concentrations perturbed the cell envelopes, leading to the loss of intracellular contents.

CONCLUSIONS

Therefore, paenipeptin C' exerts its bactericidal effect through damaging bacterial cytoplasmic membrane.

Bystander Phage Therapy: Inducing Host-Associated Bacteria to Produce Antimicrobial Toxins against the Pathogen Using Phages

Brevibacillus laterosporus is often present in beehives, including presence in hives infected with the causative agent of American Foulbrood (AFB), Paenibacillus larvae. In this work, 12 B. laterosporus bacteriophages induced bactericidal products in their host. Results demonstrate that P. larvae is susceptible to antimicrobials induced from field isolates of the bystander, B. laterosporus. Bystander antimicrobial activity was specific against the pathogen and not other bacterial species, indicating that the production was likely due to natural competition between the two bacteria. Three B. laterosporus phages were combined in a cocktail to treat AFB. Healthy hives treated with B. laterosporus phages experienced no difference in brood generation compared to control hives over 8 weeks. Phage presence in bee larvae after treatment rose to 60.8 ± 3.6% and dropped to 0 ± 0.8% after 72 h. In infected hives the recovery rate was 75% when treated, however AFB spores were not susceptible to the antimicrobials as evidenced by recurrence of AFB. We posit that the effectiveness of this treatment is due to the production of the bactericidal products of B. laterosporus when infected with phages resulting in bystander-killing of P. larvae. Bystander phage therapy may provide a new avenue for antibacterial production and treatment of disease.

Brevibacillus laterosporus isolated from the digestive tract of honeybees has high antimicrobial activity and promotes growth and productivity of honeybee's colonies

The development of novel antimicrobial drugs, as well as the discovery of novel compounds able to promote honeybee's growth, represents major challenges for modern entomology. The main aim of this study was to investigate whether Brevibacillus laterosporus isolated from the digestive tract of Saudi honeybees, Apis mellifera, was able to stimulate colony strength parameters of honeybees and to evaluate its ability to produce antimicrobial agents. Honeybees were collected in Dirab, Riyadh Region, Saudi Arabia, and microorganisms were isolated and identified by 16S ribosomal RNA analysis. Microscopic identification of the microorganism in its native state was facilitated by atomic force microscopy at high-resolution imaging. Active biological compounds were produced by submerged fermentation with B. laterosporus. The fermented broth was subjected to extraction and purification, and then semi-pure compounds were analyzed by gas chromatography-mass spectrometry. The effectiveness of the crude extract and semi-pure compounds as antimicrobial agents was evaluated by susceptibility assays. More than 22% of the microorganisms isolated from the digestive tract of healthy honeybees have been identified as B. laterosporus, this kind of species has a unique shape and morphological structure. The cyclic dipeptide cyclo(Leu-Pro) produced by B. laterosporus showed biological activity against several pathogenic microorganisms. Furthermore, the total counts of workers, closed brood, and open brood, as well as the production of bee pollen and honey, were better in honeybees treated with a B. laterosporus suspension. The data indicated that the B. laterosporus strain isolated from a healthy honeybee might be a novel probiotic and a producer of important biological compounds.

Bacillaceae-derived peptide antibiotics since 2000

Members of the Bacillaceae family, including Bacillus spp., Brevibacillus spp., Paenibacillus spp., Aneurinibacillus sp., and Halobacillus sp., are an important source of structurally diverse classes of short peptides of ∼ 30 residues or fewer possessing peculiar and rapid killing activity against various pathogens. Additionally, many have unique structures that enhance resistance to hydrolysis by proteases, and these are ideal therapeutic tools and potential alternatives to current antibiotics. The need for novel antibiotic lead compounds is urgent, and this review summarises 119 Bacillaceae compounds published since 2000, including 12 surfactin-like lipopeptides, 16 iturinic lipopeptides, fengycin C, 33 other cyclic lipopeptides, 26 linear lipopeptides, two thiopeptides, four 2,5-diketopiperazines, 20 typical cyclic peptides, and five standard linear peptides. The current and potential therapeutic applications of these peptides, including structure, antibacterial, antifungal, and antiviral activities, are discussed.