Bacteriocin-like Substance Research Articles

Biological Properties of S. warneri KYS-164 Isolated from Kefir Grains.

Staphylococcus worderi KYS-164, isolated from homemade Tibetan kefir grains, produces bacteriocin-like inhibitory substances (BLIS), which are peptides with antimicrobial properties, but have not been fully characterized. The research on BLIS will lay the foundation for mining new bacteriocins. In this study, the optimal culture conditions for the production of highly active BLIS were found to be incubation at 30 °C and 120 rpm, and the most effective extraction method was ammonium sulfate precipitation (ASP) using ammonium sulfate at 80% saturation. The postantibiotic effect (PAE) of BLIS on Staphylococcus aureus CICC 10384 is significant, with a 4 × MIC BLIS concentration able to prolong the PAE to 2.39 h. BLIS has excellent biosafety, with no deleterious effects observed at 8 × MIC concentration. Gas chromatography-ion mobility spectrometry (GC-IMS) was used to analyze the volatile compounds synthesized by Staphylococcus warneri KYS-164 during its growth. Hydroxycitronellal, ethyl pyruvate, and α-pinene were found to be unique substances produced by this strain, which can provide fresh, refreshing floral and fruity aromas as well as strong pine and resinous aromas in the process of kefir grain fermentation of milk. Analysis of the S. warneri KYS-164 genome provided insights into the major metabolic pathways in which genes expressed in this strain are involved. This study represents the first isolation of S. warneri KYS-164 from kefir grains prepared by Tibetan families, and provides a comprehensive analysis of its physicochemical properties. This research provides a solid foundation for better understanding and utilization of S. warneri KYS-164.

Natural Antimicrobial Monoterpenes as Potential Therapeutic Agents in Vaginal Infections: A Review

The recurrence and relapse of vaginal infections in women is a major issue and a challenging pathway to identify and develop new approaches to treatment. In the case of antibiotic therapy, contraceptives, and dietary changes, the recurrence of vaginitis is more common these days. Anaerobic bacteria, Candida spp., and trichomonas in the vaginal microflora cause both symptomatic and asymptomatic vaginitis, which includes vaginal inflammation. It changes the vaginal microbiota and decreases Lactobacilli spp. growth, which is maintaining the vaginal pH (3.5-4.5) through lactic acid production, antimicrobial peptides, bacteriocin, and bacteriocin-like inhibitory substances. The remarkable antimicrobial activity of plant’s producing metabolites like alkaloids, tannins, phenolic compounds, flavonoids and terpenoids for several vaginal infections have been reported in previous studies. Presented review focuses on the pivotal role of monoterpenes, providing a detailed description of thymol, geraniol, limonene, eugenol, eucalyptol, and α-terpineol as antimicrobial molecules in the treatment of vaginal infections. These monoterpenes are very good at killing E. coli, Staphylococcus aureus, Pseudomonas aeruginosa, Aspergillus niger, Trichomonas vaginalis and Candida albicans which are the main microbes that cause vaginitis. Future research could explore the latent combinations of such monoterpenes as synergistic antimicrobial agents to treat bacterial and fungal vaginal infections, trichomoniasis, among other conditions.

Bacteriocin CM175, a new high molecular weight and phage associated protein produced by Pediococcus pentosaceus CM175

Bacteriocins are proteins with antimicrobial capacity produced by different bacteria. Developing bacteriocin-based technologies could be an effective strategy to address current problems in the pharmaceutical and food industries, including limited therapeutic options against superbug infections, foodborne diseases, and food spoilage microorganisms. The lactic acid bacteria Pediococcus pentosaceus are known producers of bacteriocins. Particularly, Ped. pentosaceus strain CM175 has been reported to produce an uncharacterized bacteriocin-like inhibitory substance (BLIS) with an interesting antibacterial spectrum against Gram-positive and -negative pathogenic bacteria. The objective of the present study was to explore whether the BLIS produced by CM175 contains at least one bacteriocin, and identify it. Our results showed that the CM175 strain produced a non-previously characterized antimicrobial protein of 49 kDa identified by mass spectrometry as a phage-related protein, named bacteriocin CM175. Through fluorescence and transmission electron microscopies, it was demonstrated that bacteriocin CM175 damages the cell membrane integrity of Listeria monocytogenes through a non-lytic mechanism. Bacteriocin CM175 is the first high molecular weight and phage protein-like bacteriocin reported in Ped. pentosaceus. The results of this study open the possibility of exploring various applications directly related to the antimicrobial potential of bacteriocin CM175, including the development of antibiotics, and disinfectants.

Production of bacteriocin-like inhibitory substance (BLIS) by Staphylococcus spp. isolates from dogs.

In the present study, 39 canine isolates of Staphylococcus spp. were tested for antimicrobial substance (AMS) production. Seven AMS producers were identified, whose products exhibited a non-acidic character and a proteinaceous nature, therefore being considered bacteriocin-like inhibitory substances (BLIS). The producer strains of BLIS P1, P16 and I3 showed a broad spectrum of antimicrobial activity. Human, veterinary and plant pathogens, such as Listeria monocytogenes, Klebsiella pneumoniae, Staphylococcus spp. and Clavibacter michiganensis, were among the inhibited micro-organisms, suggesting the potential biotechnological application of these peptides. MALDI-TOF mass spectrometry and 16S rDNA sequencing identified the producer strains of BLIS P1, P16 and I3 as Staphylococcus pseudintermedius P1, Staphylococcus schleiferi P16 and Staphylococcus pseudintermedius I3. The plasmid profile of these strains suggests that the BLIS production is linked to biosynthetic genes located on plasmids. PCR analyses revealed that BLIS P1, P16 and I3 are different from 11 staphylococcins already described in the literature and that their genomic DNAs do not carry the most prevalent staphylococcal enterotoxin genes. The highest levels of BLIS production were achieved after 18-24h of growth of the producer strains in TSB medium. Moreover, BLIS P1 and I3 exhibited high resistance to temperature and pH variations, and BLIS P16 maintained 100% of its activity in almost all conditions tested. The characteristics associated with BLIS P1, P16 and I3 described in this work encourage further investigation of these substances, in addition to this study being the first report of BLIS production by a strain of S. schleiferi.

Antimicrobial Activity and Genomic Analysis of Lactococcus lactis Strains NRRL B-50571 and NRRL B-50572 Isolated from Artisanal Mexican Cheese for the Assessment of their Biotechnological Potential as Starter Cultures

ABSTRACT The objective of this study was to report the genome sequence of Lactococcus lactis NRRL B-50571 and NRRL B-50572, in silico analysis for the identification of genes related with their biotechnological potential and to evaluate the antimicrobial properties in vitro. Results demonstrated the safety of these strains, since they did not exhibit antibiotic resistance genes or links to pathogenic families. Genes related to probiotic properties, amino acid biosynthesis and catabolism, vitamin production and carbohydrate metabolism, bacteriocins and secondary metabolites were found. Also, these strains produced bacteriocin-like substances which exhibited antimicrobial activity against food indicator microorganisms (Staphylococcus aureus, Listeria innocua, Salmonella enterica subsp. enterica serovar Typhimurium, Salmonella enterica subsp. enterica serovar Choleraesuis and Escherichia coli). These findings provided valuable insights into the genomic and functional capabilities of L. lactis NRRL B-50571 and NRRL B-50572, highlighting their biotechnological significance for their use as starter cultures in the manufacture of safe dairy foods with potential health benefits.

Efficient metabolic pathway modification in various strains of lactic acid bacteria using CRISPR/Cas9 system for elevated synthesis of antimicrobial compounds

Lactic acid bacteria (LAB) are known to exhibit various beneficial roles in fermentation, serving as probiotics, and producing a plethora of valuable compounds including antimicrobial activity such as bacteriocin-like inhibitory substance (BLIS) that can be used as biopreservative to improve food safety and quality. However, the yield of BLIS is often limited, which poses a challenge to be commercially competitive with the current preservation practice. Therefore, the present work aimed to establish an optimised two-plasmid CRISPR/Cas9 system to redirect the carbon flux away from lactate towards compounds with antimicrobial activity by disrupting lactate dehydrogenase gene (ldh) on various strains of LAB. The lactic acid-deficient (ldhΔ) strains caused a metabolic shift resulting in increased inhibitory activity against selected foodborne pathogens up to 78 % than the wild-type (WT) strain. The most significant effect was depicted by Enterococcus faecalis-ldh∆ which displayed prominent bactericidal effects against all foodborne pathogens as compared to the WT that showed no antimicrobial activity. The present work provided a framework model for economically important LAB and other beneficial bacteria to synthesise and increase the yield of valuable food and industrial compounds. The present work reported for the first time that the metabolism of selected LAB can be manipulated by modifying ldh to attain metabolites with higher antimicrobial activity.

A Novel C-Terminal Truncated Bacteriocin Found by Comparison between Leuconostoc mesenteroides 406 and 213M0 Isolated from Mongolian Traditional Fermented Milk, Airag.

Bacteriocins produced by lactic acid bacteria are known to be useful tools for food biopreservation and fermentation control. Leuconostoc mesenteroides subsp. mesenteroides 406 and 213M0 isolated from different samples of Mongolian traditional fermented milk, airag, had been reported to produce listericidal bacteriocin-like inhibitory substances with similar but slightly different properties. In this study, the antibacterial properties and the related gene sequences of both strains were compared, and then their bacteriocins were purified and identified. Strain 406 was superior to strain 213M0 in cell growth and antibacterial activity against many strains. However, the activity of 213M0 was stronger than that of 406 against a few strains. DNA sequencing revealed two and three plasmids in 406 and 213M0, respectively, and each one of them harbored an almost identical mesentericin Y105-B105 gene cluster. Removal of these plasmids resulted in a complete loss of activity, indicating that the antibacterial activity of both strains was generated by bacteriocins encoded on the plasmids. Mesentericins Y105 and B105 were purified from both cultures, and another novel bacteriocin, named mesentericin M, was identified from the 213M0 culture only. Its structural gene was coded on a 213M0 plasmid and, surprisingly, its C-terminal three amino acid residues were post-translationally cleaved. To our knowledge, this is the first report of a C-terminal truncated bacteriocin. In conclusion, the novel bacteriocin should be mainly responsible for the difference in antibacterial properties between the two strains.

Antimicrobial Activities and Characterization of Bacteriocin-Like Substances Isolated from Lactic Acid Bacteria of Local Fermented Foods

Antimicrobial Activities and Characterization of Bacteriocin-Like Substances Isolated from Lactic Acid Bacteria of Local Fermented Foods

Production and SERS characterization of bacteriocin-like inhibitory substances by latilactobacillus sakei in whey permeate powder: exploring natural antibacterial potential.

Bacteriocins are antimicrobial compounds that have awakened interest across several industries due to their effectiveness. However, their large-scale production often becomes unfeasible on an industrial scale, primarily because of high process costs. Addressing this challenge, this work analyzes the potential of using low-cost whey permeate powder, without any supplementation, to produce bacteriocin-like inhibitory substances (BLIS) through the fermentation of Latilactobacillus sakei. For this purpose, different concentrations of whey permeate powder (55.15gL-1, 41.3gL-1 and 27.5gL-1) were used. The ability of L. sakei to produce BLIS was evaluated, as well as the potential of crude cell-free supernatant to act as a preservative. Raman spectroscopy and surface-enhanced Raman scattering (SERS) provided detailed insights into the composition and changes occurring during fermentation. SERS, in particular, enhanced peak definition significantly, allowing for the identification of key components, such as lactose, proteins, and phenylalanine, which are crucial in understanding the fermentation process and BLIS characteristics. The results revealed that the concentration of 55.15gL-1 of whey permeate powder, in flasks without agitation and a culture temperature of 32.5°C, presented the highest biological activity of BLIS, reaching 99% of inhibition of Escherichia coli and Staphylococcus aureus with minimum inhibitory concentration of 36-45%, respectively. BLIS production began within 60h of cultivation and was associated with class II bacteriocins. The results demonstrate a promising approach for producing BLIS in an economical and environmentally sustainable manner, with potential implications for various industries.

Effect of Enterococin – Zinc Oxide Nanoparticles on Gene Expression of rsbA Swarming Genes in Proteus mirabilis isolation Catheter urine.

Urinary tract infections linked to catheters are believed to be caused most frequently by Proteus mirabilis. It produces urease, which greatly increases the potency of catheter occlusion caused by swarming. Pathogenic bacteria use swarming as one of their main virulence mechanisms to evade antibiotics; as a result, there is an increasing need to develop novel antibiotic substitutes. Investigating the possible antibiofilm capabilities of artificial zinc oxide nanoparticles (ZnO NPs) made from E. Faecium was the aim of this study. By generating reductive enzymes, bacterial cells are able to catalyze the biosynthesis process. Bacteriocin-like inhibitory substance (BLIS) was used to create the nanoparticles. AFM, TEM, FESEM, and other analytical tools were used to characterize the synthesized zinc nanoparticles and determine the chemical and physical characteristics of the products. Weak swarming is shown by microorganisms that develop strong swarming. After incubation, the ZnO nanoparticles were incubated for 24 or 48 hours at 37°C at a sub-MIC of 32 µg/ml. After these isolates were treated with zinc nanoparticles, downregulation of rsbA expression was detected via real-time PCR compared to that in the untreated isolates. Zinc oxide nanoparticles can serve as antibacterial agents in a concentration-dependent manner, according to all of the study's findings. This was demonstrated by the notable downregulation of rsbA gene expression, which effectively inhibits the production of biofilms and swarming motility. This was demonstrated by their noteworthy downregulation of rsbA gene expression, which effectively promoted swarmed motility.

Antagonistic Activity of Bacteriocin-like Inhibitory Substances from Enterococcus lactis Isolated from the Surface of Jalapeno Pepper against Foodborne Pathogens

Lactic acid bacteria (LAB) can produce peptides known as bacteriocins with antagonistic activity against foodborne pathogens. The potential of LAB isolated from the surface of jalapeno peppers to produce bacteriocins with antagonistic activity against Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7, and Salmonella Typhimurium was evaluated. Previously isolated LAB strains were reactivated, and their cell-free supernatants (CFSs) were evaluated. Out of 390 reactivated strains, 60 produced bacteriocin-like inhibitory substances (BLIS) since their antagonistic activity was lost after proteases addition. Subsequently, 16 BLIS showed heat resistance (HR-BLIS), retaining their bioactivity after heat treatment (121 °C for 15 min). By 16S rRNA gene sequencing and antibiotic susceptibility tests, LAB strains producing HR-BLIS were identified as Enterococcus lactis. Four HR-BLIS exhibited a minimum inhibitory concentration (MIC) of 80 mg/mL against L. monocytogenes. MIC and minimum bactericidal concentration (MBC) of HR-BLIS-67 for S. aureus (MIC = 80 mg/mL; MBC = 320 mg/mL), S. Typhimurium (MIC = 150 mg/mL; MBC = 250 mg/mL), and E. coli O157:H7 (MIC = 250 mg/mL; MBC = 400 mg/mL) were determined. LAB isolated from the surface of jalapeno pepper produced HR-BLIS (possibly enterocin) that exhibited broad-spectrum antagonistic activity against foodborne pathogens; therefore, they are a promising source of natural antimicrobials to ensure food safety.

The Enterococcus secretome inhibits the growth of vancomycin-resistant Enterococcus faecalis V853 with their antiproliferative properties and nanoencapsulation effects.

In our study, the secretome of the clinical isolate Enterococcus faecalis HY7 displayed antibacterial activity against the vancomycin-resistant Enterococcus faecalis V853. These bacteriocin-like substances showed thermal stability at a wide range of temperatures up to 121°C, while proteinase K treatment resulted in a total loss of their activity. PCR-based screening for bacteriocin biosynthetic genes revealed that Enterococcus faecalis HY7 harbored multiple enterocin-producing genes, including ent A, avc A, and as-48. The production kinetics demonstrated the highest levels of bacteriocins production at 16h, whereas the activity was diminished after 32h of microbial growth. Notably, the partially purified bacteriocins exhibited anti-proliferative activity on the colon cancer cells, Caco2, with an IC50 value of 172.8μg/mL. Remarkably, the nanoencapsulation of our bacteriocins in liposome showed a fourfold increase in its anti-vancomycin-resistant Enterococcus activity, which is the first report of liposome encapsulation with anti-vancomycin resistant Enterococcus bacteriocin.

Selection of starter lactic acid bacteria capable of forming biofilms on wooden vat prototypes for their future application in traditional Sicilian goat's milk cheese making

In this study, 327 presumptive lactic acid bacteria (LAB) were isolated from goats' milk acid curds produced at a Sicilian dairy farm with the aim to identify potential starter cultures for traditional cheeses. All isolates were first processed by randomly amplified polymorphic DNA (RAPD)-PCR analysis. This approach identified 63 distinct strains which were evaluated for their acidifying capacity. Only 15 strains specifically stood out for their acidification capacity and were identified through 16S rRNA gene sequencing as Lactococcus lactis (11 strains) Enterococcus faecalis (three strains), and Ligilactobacillus animalis (one strain). Notably, all 15 LAB isolates produced bacteriocin-like inhibitory substances and anti-biofilm compounds, against both planktonic and biofilm forms of Listeria monocytogenes, Salmonella Enteritidis, Escherichia coli, and Staphylococcus aureus, albeit at varying levels. Among these 15 LAB, En. faecalis RGM25 and Lc. lactis RGM55, susceptible to five antibiotics tested, were put in contact with wooden vat prototypes, because all equipment used in traditional cheese production in Sicily are made of wood. Scanning electron microscopy and bacterial plate counts of the wooden vat prototypes showed the development of biofilms at levels of approximately 6.0 log CFU/cm2. Overall, this study contributes to establishing a custom-made LAB starter cultures with bio-preservatives properties for Sicilian cheese productions.

Lactic Acid Bacteria and Bacillus subtilis as Potential Protective Cultures for Biopreservation in the Food Industry

The use of bacteria and/or their compounds is an alternative to the use of positive-list additives that the food industry is using as a tool to meet consumer demands for more natural, long-shelf-life, and healthy products, in short, to offer clean label foods. The aim of this study is to investigate the suitability of cell-free supernatants (CFSs) from Qualified Presumption of Safety strains as bioprotective cultures. Out of an initial screening panel of about 200 isolates, strains Pediococcus acidilactici CNTA 1059, Lactiplantibacillus plantarum CNTA 600, Levilactobacillus brevis CNTA 1374, and Bacillus subtilis CNTA 517 demonstrated strong antimicrobial activity against, especially, Gram-positive bacteria. The CFSs of these four strains showed minimum inhibitory concentration values between 0.15% and 5% against Listeria monocytogenes and Lentilactobacillus parabuchneri. None of the four selected strains exhibited acquired resistance to target antibiotics, and the non-toxigenicity of all the CFSs was demonstrated. In the case of the three lactic acid bacteria, the presence of bacteriocin-like inhibitory substances was confirmed following the decline in antimicrobial activity due to treatment with proteases. Regarding B. subtilis, biosynthetic gene clusters for different bacteriocin-like substances, including protease-resistant lipoproteins, were found via whole-genome sequencing. In addition, all of the CFSs exhibited stable antimicrobial activity at a wide range of temperatures (70–121 °C) used for the pasteurization and sterilization of food products, with a loss of antimicrobial activity ranging from 3% to 28%. These results point to the possibility that CFSs from these strains could be used in the food industry as a biocontrol tool to develop new products.

Evaluation of the Effect of Lactobacillus acidophilus ATCC 4356 Bacteriocin against Staphylococcus aureus.

Lactobacillus acidophilus is lactic acid bacteria that produce bacteriocins. Bacteriocins are antimicrobial peptides or proteins that exhibit activity against closely related bacteria. The aim of this study was to determine the effect of L. acidophilus ATCC 4356 bacteriocin against Staphylococcus aureus. Material and Methods. We used four different phenotypic methods for antimicrobial activities against two standard strains: methicillin-resistant S. aureus (MRSA) ATCC 33591 and methicillin-susceptible S. aureus (MSSA) ATCC 25923. The methods were (1) agar well diffusion, (2) overlay soft agar, (3) paper disk, and (4) modification of punch hole. The ammonium sulfate method was used to concentrate crude bacteriocin, and ultrafiltration and dialysis tubes were used to remove ammonium sulfate from the bacteriocins. Each method was repeated in triplicate. L. acidophilus ATCC 4356 showed antimicrobial activity against both MRSA and MSSA standard strains only by the overlay soft agar method and not by the agar well diffusion, punch hole modification, and paper disk methods. No antimicrobial effects were observed in crude bacteriocins concentrated. The growth inhibition of S. aureus in overlay soft agar method may be due to the production of bacteriocin-like substances. The overlay soft agar method is a qualitative test, so there is a need for further study to optimize the conditions for the production of bacteriocin-like substances in the culture supernatant and precise comparison between the inhibitory activity and pheromone secretion of different strains.

Characterization of the broad-spectrum antibacterial activity of bacteriocin-like inhibitory substance-producing probiotics isolated from fermented foods

Antimicrobial peptides, such as bacteriocin, produced by probiotics have become a promising novel class of therapeutic agents for treating infectious diseases. Selected lactic acid bacteria (LAB) isolated from fermented foods with probiotic potential were evaluated for various tests, including exopolysaccharide production, antibiotic susceptibility, acid and bile tolerance, antibacterial activity, and cell adhesion and cytotoxicity to gastric cell lines. Six selected LAB strains maintained their high viability under gastrointestinal conditions, produced high exopolysaccharides, showed no or less cytotoxicity, and adhered successfully to gastric cells. Furthermore, three strains, Weissella confusa CYLB30, Lactiplantibacillus plantarum CYLB47, and Limosilactobacillus fermentum CYLB55, demonstrated a strong antibacterial effect against drug-resistant Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enterica serovar Choleraesuis, Enterococcus faecium, and Staphylococcus aureus. Whole genome sequencing was performed on these three strains using the Nanopore platform; then, the results showed that all three strains did not harbor genes related to toxins, superantigens, and acquired antimicrobial resistance, in their genome. The bacteriocin gene cluster was found in CYLB47 genome, but not in CYLB30 and CYLB55 genomes. In SDS-PAGE, the extract of CYLB30 and CYLB47 bacteriocin-like inhibitory substance (BLIS) yielded a single band with a size of less than 10 kDa. These BLIS inhibited the growth and biofilm formation of drug-resistant P. aeruginosa and methicillin-resistant S. aureus (MRSA), causing membrane disruption and inhibiting adhesion ability to human skin HaCaT cells. Moreover, CYLB30 and CYLB47 BLIS rescued the larvae after being infected with P. aeruginosa and MRSA infections. In conclusion, CYLB30 and CYLB47 BLIS may be potential alternative treatment for multidrug-resistant bacteria infections.

Anti-Listerial Activity of Bacteriocin-like Inhibitory Substance Produced by Enterococcus lactis LBM BT2 Using Alternative Medium with Sugarcane Molasses.

Listeria monocytogenes is a foodborne pathogen that contaminates food-processing environments and persists within biofilms on equipment, thus reaching final products by cross-contamination. With the growing demand for clean-label products, the search for natural antimicrobials as biopreservants, such as bacteriocins, has shown promising potential. In this context, this study aimed to evaluate the anti-listerial action of bacteriocins produced by Enterococcus lactis LBM BT2 in an alternative medium containing sugarcane molasses (SCM). Molecular analyses were carried out to characterize the strain, including the presence of bacteriocin-related genes. In the kinetic study on SCM medium E. lactis, LBM BT2 showed biomass and bacteriocin productions similar to those observed on a sucrose-based medium (control), highlighting the potential of the sugarcane molasses as a low-cost substrate. Stability tests revealed that the molecule remained active in wide ranges of pH (4-10) and temperature (60-100 °C). Furthermore, the proteolytic treatment reduced the biomolecule's antimicrobial activity, highlighting its proteinaceous nature. After primary purification by salting out and tangential flow filtration, the bacteriocin-like inhibitory substance (BLIS) showed bacteriostatic activity on suspended L. monocytogenes cells and against biofilm formation at a concentration of 0.625 mg/mL. These results demonstrate the potential of the produced BLIS as a biopreservative in the food industry.

Isolation and characterization of lactic acid bacteria producing a potent anti-listerial bacteriocin-like inhibitory substance (BLIS) from chhurpi, a fermented milk product.

Nowadays, the bacteriocin industries have seen significant growth, supplanting chemical preservatives in its ability to improve the shelf-life and safety of food. The increasing customer desire to use natural preservatives has fueled advancing bacteriocin research. The objective of this study was to identify lactic acid bacteria (LAB) that produce bacteriocin-like inhibitory substance (BLIS) and have strong anti-listerial activity. We have identified and analyzed a LAB obtained from chhurpi samples, a popular milk-derived product in the Himalayan regions of India and Nepal. The strain was studied and identified based on its morphological, biochemical, and physiological characteristics. Furthermore, the molecular 16s-rDNA analysis suggests that the strain was Lactococcus sp. RGUAM1 (98.2% similar to Lactococcus lactis subsp. hordniae NBRC 100931T). The isolated strain can produce a potent BLIS, which has shown efficacy against three gram-positive bacteria responsible for food spoilage, such as Listeria monocytogenes (MTCC 657), Staphylococcus aureus subsp. aureus (MTCC 87), Lactobacillus plantarum (MTCC 1407), Lactobacillus paraplantarum (MTCC 12904). The scanning electron microscope (SEM) image illustrates that the crude cell-free supernatant (CFS) disrupts the cell envelope, leading to the release of cellular contents and the clustering of cells. In addition, this BLIS can easily withstand a wide range of pH (2-12), temperature (up to 100°C for 15min), bile salt (0.3% W/V), salinity (4% W/V), and enzyme activity of 1600AU/ml against Listeria monocytogenes. Our research offers a robust framework and valuable insights into bio-preservation and its potential applications in diverse food products.

Enterococcus faecium BACTERIOCIN EFFLUX PUMP MexA GENE AND PROMOTE SKIN WOUND HEALING IN MICE

The process involved isolating E. faecium from the gut of honeybees, screening the bacterium for bacteriocin-like inhibitory substance (BLIS), evaluating its impact on the expression of the mexA gene in multidrug-resistant (MDR) P. aeruginosa, and determining the role of bacteriocin in treating infected wounds in mice through histopathological examination. After evaluating the best circumstances for producing BLIS, it was discovered that glucose was a superior carbon source and yeast extract was the best source of nitrogen. The pH was found to be 5, the ideal incubation time was 72 hours, and ammonium sulfate salt was used for partial purification at 80% saturation. The identification of MDR P. aeruginosa isolates from pus infections was a further focus of the study. The VITEK 2 system was used to perform the identification. The results of antibiotic susceptibility tests revealed that the greatest resistance rates were found against Meropenem (83.3%) and Gentamicin (73.3%), followed by beta-lactam antibiotics (Ticarcillin, Ticarcillin/Clavulanic Acid, Piperacillin, and Aztreonam), which showed resistance in about 66.6 and 36.6% of the study isolates, respectively. Followed by Imipenem (63.3%), Ceftazidime (36.6%), and Cefepime (36.6%). The mexA gene was detected in all nine strains. The study also investigated the impact of the bacteriocin of the chosen strain on the expression of the mexA gene. An in vivo study revealed that wound healing was enhanced by treating infected wounds with E. faecium bacteriocin. Conclusion: Down-regulation and up-regulation in the expression of the genes following exposure to Bacteriocin indicate the potential of E. faecium as an effective antimicrobial agent against MDR P. aeruginosa infections.

The role of proteinaceous toxins secreted by Staphylococcus aureus in interbacterial competition.

Staphylococcus aureus is highly adapted to colonization of the mammalian host. In humans the primary site of colonization is the epithelium of the nasal cavity. A major barrier to colonization is the resident microbiota, which have mechanisms to exclude S. aureus. As such, S. aureus has evolved mechanisms to compete with other bacteria, one of which is through secretion of proteinaceous toxins. S. aureus strains collectively produce a number of well-characterized Class I, II, and IV bacteriocins as well as several bacteriocin-like substances, about which less is known. These bacteriocins have potent antibacterial activity against several Gram-positive organisms, with some also active against Gram-negative species. S. aureus bacteriocins characterized to date are sporadically produced, and often encoded on plasmids. More recently the type VII secretion system (T7SS) of S. aureus has also been shown to play a role in interbacterial competition. The T7SS is encoded by all S. aureus isolates and so may represent a more widespread mechanism of competition used by this species. T7SS antagonism is mediated by the secretion of large protein toxins, three of which have been characterized to date: a nuclease toxin, EsaD; a membrane depolarizing toxin, TspA; and a phospholipase toxin, TslA. Further study is required to decipher the role that these different types of secreted toxins play in interbacterial competition and colonization of the host.