Bacteriocins: Properties and potential use as antimicrobials

Leuconostoc mesenteroides strain MS4-derived bacteriocins: A potent antimicrobial arsenal for controlling Xylella fastidiosa infection

Xylella fastidiosa subsp. pauca (Xfp) currently presents a serious threat to agriculture in Europe and in the Mediterranean, following its discovery in several countries. Addressing this bacterial plant disease with traditional agricultural practices and management strategies has proven inadequate, highlighting the urgent need for effective and environmentally safe antibacterial solutions. In this study, we explored the antibacterial activity of the lactic acid bacterium Leuconostoc mesenteroides strain MS4-derived bacteriocins against Xfp, utilizing a combination of in vitro and in planta experiments. In particular, the cell-free precipitate (CFP) derived from strain MS4 culture in MRS broth, suppressed Xfp growth on BCYE agar plate, whereas protease K-treated CFP was inactive, highlighting the presence of antimicrobial compounds of proteinaceous nature. Additionally, fluorescence and transmission electron microscopy analyses showed that the CFP exhibits a bactericidal effect on Xfp cells, characterized by membrane disruption and subsequent cellular damage. The whole-genome sequencing and bioinformatic analysis revealed that MS4 genome consists of a circular chromosome of 1860,891 bp and a circular plasmid of 37,317 bp and most importantly to encompass six bacteriocin-encoding genes, with a peptide size ranging from 45 to 59 amino acids. MALDI-TOF/TOF MS and RPLC-ESI-MS assays performed on cell-free supernatant (CFS) confirmed the secretion of four (out of 6) bacteriocins (denoted MK-45, MR-53, MW-56, and MG-58) by MS4 in MRS broth. In spot assays, these bacteriocins displayed significant lethality against Xfp, with a minimum lethal concentration between 0.2 and 0.4 mg/mL. The application of CFP on Xfp-infected Nicotiana benthamiana plants, implemented both as preventive and curative approach, successfully controlled the infection, resulting in no visible symptoms 40 days post-inoculation. The finding of MS4 as a natural source of various potent bacteriocins against Xfp, coupled with a significant production under low-cost and uncomplicated laboratory conditions, make of MS4 a cost-effective and realistic option for sustainable management of Xf-related diseases.

Microbial dynamics and Pseudomonas natural product production in milk and dairy products

Covering: 2000 up to the first half of 2024Milk and its derived dairy products have long been integral to the human diet, with evidence of consumption dating back over 9000 years. Milk's high nutritional value renders dairy products an important element of human diet while also offering a fertile environment for microbial growth. Beneficial microorganisms in dairy products are often associated with biogenic and probiotic effects, whereas spoilage or pathogenic microorganisms can pose health risks. Fermentation is a key method to preserve milk. Whereas dairying practices in most parts of the world have been highly altered by industrialization over the past century, nomadic pastoralists in Mongolia notably retain a rich tradition of household-level dairy fermentation that has been practiced since 3000 BC. Milk-associated microorganisms produce a vast number of low molecular weight natural products that can mediate beneficial and detrimental interactions. Bacteria of the genus Pseudomonas are found in traditional Mongolian dairy products and are common contaminants in commercial dairy products, and they can strongly impact the quality and shelf-life of dairy products. These bacteria are well known for their ability to produce a variety of secondary metabolites, including nonribosomal (lipo)peptides, which are both structurally and functionally diverse. Lipopeptides can have antimicrobial properties, act as quorum sensing molecules, and contribute to biofilm formation due to their amphiphilic nature. Although often associated with spoilage, some of these natural products can also exhibit positive effects with potential beneficial applications in the dairy industry. This review aims to provide a comprehensive overview of the interplay between culinary fermentation and the production and activities of microbial-derived natural products.

Unveiling the anti-biofilm potential of bee venom against multi-drug resistant human pathogenic bacteria and fungi: perspectives into the efficacy and Possible mechanisms

Bacterial biofilms pose significant challenges in treating infectious diseases due to antibiotic resistance. Finding alternative natural antimicrobial agents is crucial. Bee products, long valued for their nutritional and therapeutic benefits, exhibit potent antibacterial properties. This study investigates bee venom's antibacterial activity against biofilms formed by isolated microorganisms. Biofilm formation of pathogenic bacteria and yeast isolated from cannula was studied using two models: 96-well plates and alginate beads. We showed that low doses of bee venom effectively combat biofilms of bacterial and yeast strains. Antibiofilm assays employed in this study revealed the efficacy of bee venom against biofilms formed by multi-drug resistant Staphylococcus aureus, Pseudomonas aeruginosa and Canndida species isolates. We investigated the potential of bee venom to specifically target pathogenic bacteria while sparing commensal bacteria, showing minimal effects on the commensal bacteria tested in this study. The cytotoxicity of bee venom was evaluated on normal human fibroblast cells (HFB4), revealing a half maximal inhibitory concentration (IC50) of 7 mg/mL, which is substantially higher than the effective antibiofilm dose (0.5 μg/mL) used against pathogenic bacteria and yeast strains tested in this study. Gene expression analysis further indicated that bee venom treatment influences genes associated with biofilm formation, specifically icaA and icaD in Staphylococcus aureus, as well as genes related to efflux pump activity, including nfxB, which contribute to biofilm persistence in Pseudomonas aeruginosa. Additionally, we employed electron microscopy imaging of single cells and biofilms treated with bee venom to visualize the effects of bee venom. Furthermore, Molecular docking studies employed in this study demonstrate exclusively that bee venom components bind efficiently to antibiotic-resistant determinants, virulence factors, and quorum sensing regulators in the isolated pathogenic bacteria and yeasts, highlighting the need of further explorations into in vivo effects and underlying mechanisms.

Genome mining and metabolite profiling illuminate the taxonomy status and the cytotoxic activity of a mangrove-derived Microbacterium alkaliflavum sp. nov

The genus Microbacterium in the phylum Actinomycetota contains over 100 species to date that little is known about their bioactive metabolites production. In this study, a mangrove sediment-derived strain B2969T was identified as a novel type strain within the genus Microbacterium due to the low 16S rRNA gene sequence similarity (< 99%), and low overall genome relatedness indices (ANI, 75.4%-79.5%; dDDH, 18.5%-22.7%, AAI, 68.7%-76.3%; POCP, 48.3%-65.0%) with the validly named species of the genus. The type strain B2969T (= MCCC 1K099113T = JCM 36707 T) is proposed to represent Microbacterium alkaliflavum sp. nov.. The crude extracts of strain B2969T showed weak cytotoxicity against NPC cell lines TW03 and 5-8F, with IC50 values of ranging from 3.5 µg/µL to 2.4 µg/µL respectively. Genome analysis of strain B2969T found 8 clusters of genes responsible for secondary metabolite biosynthesis, including cytotoxic compounds desferrioxamines. In addition, the application of liquid chromatography tandem mass spectrometry (LC-MS/MS)-based molecular networking strategy led to the identification of 10 compounds with potent cytotoxic activity in ethyl acetate extracts of strain B2969T. Results from the cytotoxicity assay, genome mining, and metabolite profiling based on LC-MS/MS analysis revealed its ability to produce bioactive compounds.BackgroundMangrove ecosystems are largely unexplored sources of Actinomycetota, which represent potential important reservoirs of bioactive compounds. The genus Microbacterium in the phylum Actinomycetota contains over 100 species to date that little is known about their bioactive metabolites production. In this study, a novel species, namely B2969T, within the genus Microbacterium that showed cytotoxicity against nasopharyngeal carcinoma (NPC) cell lines was isolated from mangrove sediments. Genome mining and metabolic profiling analyses were explored here to assess its biosynthetic potential of metabolites with cytotoxic properties.ResultsHere, a mangrove sediment-derived strain B2969T was identified as a novel species within the genus Microbacterium due to the low 16S rRNA gene sequence similarity (< 99.0%), and low overall genome relatedness indices (ANI, 75.4%-79.5%; dDDH, 18.5%-22.7%, AAI, 68.7%-76.3%; POCP, 48.3%-65.0%) with the type strains of this genus. We proposed that strain B2969T represents a new species, in which the name Microbacterium alkaliflavum sp. nov. is proposed. The strain showed weak cytotoxicity against NPC cell lines TW03 and 5-8F, with IC50 values of ranging from 3.512 µg/µL to 2.428 µg/µL respectively. Genome analysis of strain B2969T found 8 clusters of genes responsible for secondary metabolite biosynthesis, including desferrioxamines. In addition, the application of liquid chromatography tandem mass spectrometry (LC-MS/MS)-based molecular networking strategy led to the identification of 10 potent cytotoxic compounds in ethyl acetate extracts of strain B2969T.ConclusionsThis study confirmed the taxonomy status of type strain B2969T (= MCCC 1K099113T = JCM 36707 T) within the genus Microbacterium, in which the name Microbacterium alkaliflavum sp. nov.. Results from the cytotoxicity assay, genome mining, and metabolite profiling based on LC-MS/MS analysis revealed its ability to produce bioactive substances, providing sufficient evidence for the potential of Microbacterium species in the discovery of novel pharmaceuticals.

Investigating the production and synergistic antibacterial activity of bacteriocin-like substance from Brevibacillus laterosporus SA-14 (TISTR 2453) for enhanced wound healing

The rise in antimicrobial-resistant (AMR) bacteria, especially Methicillin-resistant Staphylococcus aureus (MRSA), is a global health concern. Bacteriocins are promising antibiotic alternatives. This study aimed to enhance the production of bacteriocin-like substances (BLS) from Brevibacillus laterosporus SA-14 (TISTR 2453) by optimizing nutrients, evaluating antibacterial activity, assessing synergy with vancomycin, and testing the cytotoxicity and wound healing effects on human keratinocytes. The results showed that when the SA-14 strain was cultured in half-formula Luria-Bertani broth (LB/2) with added carbon sources (glucose, sucrose, and lactose), all cultures reached the late log phase at 24 h, and antibacterial activity was exhibited against various MRSA strains after 48 h, except for the LB/2 supplemented with glucose, likely due to carbon catabolite repression. However, the addition of nitrogen sources, including skim milk, peptone, and beef extract resulted in high antibacterial activity at 48 h, with skim milk being the most effective for BLS production. The BLS was precipitated with 80 % ammonium sulfate, achieving a 38.09 % yield and a protein concentration of 6.97 ± 1.12 mg/mL. The SDS-PAGE analysis revealed five bands of proteins with molecular weights of 25-250 kDa. The minimum inhibitory concentration of BLS ranged from 0.44 to 0.87 mg/mL, with an minimum bactericidal concentration) of 0.87 mg/mL for all MRSA strains. A synergistic effect with vancomycin was observed at 0.22 mg/mL BLS and 1 μg/mL vancomycin, with an fractional inhibitory concentration index of 1.00, indicating an additive effect. At a concentration of 0.22 mg/mL, BLS was non-cytotoxic to HaCaT cells and promoted complete wound healing after 48 h. Therefore, BLS produced by the SA-14 strain is suitable for controlling AMR, especially MRSA, and has the potential for application in wound dressings in the future.

Evaluation of the activity and molecular characterisation of bacteriocins produced by E. faecium and E. faecalis isolated from different hosts against public health-threating pathogens

The aim of the study was to assess the activity and genetic background of bacteriocins of E. faecium and E. faecalis isolated from different hosts against methicillin-resistant Staphylococcus aureus (MRSA), E. faecium and E. faecalis with vancomycin (VRE) and high-level aminoglycoside (HLAR) resistance, Streptococcus agalactiae, and Listeria monocytogenes. The research was carried out using qualitative method and partially purified bacteriocins. The occurrence of 12 bacteriocin genes was examined and their sequences were analysed. Bacteriocins showing inhibitory activity against indicator strains were isolated from 95 % of E. faecium and 50 % of E. faecalis gave positive results in qualitative method. The highest inhibitory activity of bacteriocins isolated from E. faecium was obtained against E. faecium (100-25600AU/ml), E. faecalis VRE/HLAR (100-12800AU/ml), and L. monocytogenes (100-6400AU/ml), while bacteriocins isolated from E. faecalis were active against L. monocytogenes (100-25600AU/ml). The lowest activity of bacteriocins isolated from both Enterococcus species was determined against S. agalactiae (100AU/ml) and MRSA (100-800AU/ml). The presence of at least one bacteriocin gene was detected in 95 % of E. faecium and 52 % of E. faecalis. Four genes encoding bacteriocins was found (entB, enxAB, entA, entP), with the highest frequency of entA (97 %) in E. faecium and entB (53 %) in E. faecalis. The changes observed in the nucleotides among the entA, entB, and enxAB genes did not affect the activity of the bacteriocins. To sum up, E. faecium and E. faecalis may be a source of bacteriocins inhibiting the growth of drug-resistant bacteria, such as MRSA, HLAR, VRE, and L. monocytogenes.

In silico analysis of bacteriocins from Lactobacillus acidophilus membrane vesicles against Streptococcus mutans GtfB protein

Oral pathogens pose a significant global health concern, affecting 80% of the world's population across all age groups. Among these pathogens, Streptococcus mutans stands out as a prominent threat. The rise in antibiotic resistance has limited the effectiveness of conventional antibiotics. In contrast, probiotics produce antibacterial peptides known as bacteriocins, which exhibit inhibitory effects against closely related and even unrelated bacterial species. Specifically, Lactobacillus acidophilus bacteriocins are encapsulated within membrane vesicles (MVs), allowing for long-distance transport and targeted delivery. However, no prior studies have investigated L. acidophilus membrane MV-encapsulated bacteriocins against S. mutans. In this study, we employed in-silico methods to target bacteriocins from MVs of L. acidophilus, against the GtfB virulence protein of S. mutans. Our findings indicate that Lactacin B exhibits non-toxic, non-antigenic, and non-hemolytic properties, making it a promising bioactive peptide candidate. Notably, Lactacin B forms strong interactions with GtfB in the active site, with a binding energy of -15.1 kcal/mol and four hydrogen bonds. MD simulations for 100 ns and MMPBSA assays of the complex further support the efficient binding. The fluctuation of RMSD and RMSF is minimal and corresponds to greater stability of the complex. Lactacin B interaction with gtfB mightreduce GtfB's virulence potential, and hinder S. mutans adhesion to oral surfaces, subsequently mitigating biofilm formation and preventing dental caries. However, additional in vitro studies are necessary to validate these findings.

The potential of Streptococcus pyogenes and Escherichia coli bacteriocins in synergistic control of Staphylococcus aureus

Staphylococcus aureus has developed resistance to most conventional antibiotics and is a causative agent of serious infections. Alternative therapies are urgently needed. Bacteriocins are ribosomally synthesized antimicrobial peptides produced by bacteria, including Escherichia coli (E. coli) and Streptococcus pyogenes (S. pyogenes), and represent a potential solution. While several bacteriocins have shown promise, their synergy with bacteriocins from other bacterial species remains largely unexplored. This work used agar diffusion on Muller-Hinton Agar (MHA) with S. aureus as a test bacterium to evaluate E. coli, S. pyogenes and their combined bacteriocins. The bacteriocins of S. pyogenes showed the maximum antimicrobial activity of zone of inhibition (ZOI), 24.93 mm, compared to that of E. coli bacteriocin, which was 19.28 mm, and that of the combined ones at 100% concentration, 22.6 mm. The combined bacteriocins at 50% concentration showed a reduced activity of 18.35 mm. These observations suggest that the bacteriocins produced by S. pyogenes have higher specificity and activity against S. aureus, making them effective therapeutic agents in the fight against multidrug-resistant infections.

Optimization of Culture Medium Ingredients and Culture Conditions for Bacteriocin Production in Lactococcus lactis NCU036019

Bacteriocin lactococcin036019 was identified and characterized from Lactococcus lactis NCU036019, which displayed significant antibacterial activity toward foodborne pathogenic bacteria Staphylococcus aureus under various conditions. However, the in situ low-level expression of lactococcin036019 severely limited its wide application in food industry. In this study, we optimized the medium ingredients and culture conditions of L. lactis NCU036019 for maximum production of lactococcin036019. The effects of different carbon sources, nitrogen sources, inorganic salts, growth factors, surfactants, and buffer salts on the production of bacteriocin were studied using antibacterial titer and diameter of inhibitory zone as evaluation indexes. Through single-factor experiments, Plackett-Burman (PB) experiment, steepest ascent experiment and response surface methodology, yeast extract, zinc sulfate, sodium acetate, mannitol, Tween-80, and dipotassium hydrogen phosphate were identified to display significant influence on the production of bacteriocin. By optimizing Man Rogosa and Sharpe (MRS) culture medium ingredients, the antibacterial activity of lactococcin036019 in the cell-free supernatant raised from 46.19 to 300.14 Au/mL, namely, 6.5 times increased. Furthermore, the culture conditions, such as inoculation amount, culture time, and culture temperature, were optimized, and this further increased the antibacterial activity to 409 Au/mL, namely, 8.8 times increased. This study investigated the effects of culture media and conditions on the production of lactococcin036019, and they were optimized for a maximum harvest of bacteriocin, and the significant increase of bacteriocin production in L. lactis NCU036019 facilitates the application of the antibacterial substance in future work.

Bacteriocin-Producing Staphylococci and Mammaliicocci Strains for Agro-Food and Public Health Applications with Relevance of Micrococcin P1

Antimicrobial-producing strains and their bacteriocins hold great promise for the control of bacterial diseases, being an attractive alternative to antibiotics. Thus, the aim of this study was to evaluate the inhibitory activity of 15 bacteriocin-producing staphylococci and mammaliicocci (BP-S/M) strains and their pre-purified extracts with butanol (BT) against a collection of 27 harmful or zoonotic strains (including Gram-positive/-negative bacteria and molds) with relevance in the public health and agro-food fields. These indicators (excluding Gram-negative strains) were grouped into seven categories based on their potential application areas: dairy livestock mastitis, avian pathogen zoonoses, swine zoonoses, food safety, aquaculture, wine making, and mushroom cultivation. In addition, cross-immunity assays between the BP-S/M strains were carried out to identify potential strain combinations to enhance their activity against pathogens. Finally, the hemolytic and gelatinase activities were tested in the BP-S/M strains. A strong inhibitory capacity of the BP-S/M strains was verified against relevant Gram-positive indicators, such as methicillin-resistant Staphylococcus aureus, Listeria monocytogenes, and Clostridium perfringens, among others, while no activity was detected against Gram-negative ones. Interestingly, several BT extracts inhibited the two mold indicators included in this study as representants of mushroom pathogens. The Micrococcin P1 producer Staphylococcus hominis C5835 (>60% of indicators were intensively inhibited by all the methods) can be proposed as a potential candidate for the control of bacterial diseases in the aforementioned categories alone or in combination with other BP-S/M strains (mainly with Staphylococcus warneri X2969). In this regard, five potential combinations of BP-S/M strains that enhanced their activity against specific pathogens were detected.

Antimicrobial activity of Lactobacillus spp. isolated from fermented foods and their inhibitory effect against foodborne pathogens

Lactic acid bacteria (LAB), known for their health benefits, exhibit antimicrobial and antibiofilm properties. This study investigated the cell-free supernatant (CFS) of Lactobacillus spp., particularly L. plantarum KR3, against the common foodborne pathogens S. aureus, E. coli and Salmonella spp. Lactobacillus strains were isolated from cheese, pickles and yoghurt. They were then identified by morphological, physiological and biochemical characteristics and confirmed by 16S rRNA gene sequencing. Culture supernatants from seven lactobacilli isolates showed varying inhibitory activities. Notably, L. plantarum KR3 and L. pentosus had the highest bacteriocin gene counts. L. plantarum KR3 CFS demonstrated significant antibacterial activity, with inhibition zones of 20 ± 0.34 mm for S. aureus, 23 ± 1.64 mm for E. coli, and 17.1 ± 1.70 mm for Salmonella spp. The CFS also exhibited substantial antibiofilm activity, with 59.12 ± 0.03% against S. aureus, 83.50 ± 0.01% against E. coli, and 60. ± 0.04% against Salmonella spp., which were enhanced at the minimum inhibitory concentration (MIC). These results highlighted the potential of L. plantarum KR3 in antimicrobial applications, however, further research is needed to evaluate its viability and functional properties for probiotic use. Additionally, the CFS demonstrated exceptional thermal stability, reinforcing its promise as an antimicrobial agent.

Identification and characterization of a novel bacteriocin PCM7-4 and its antimicrobial activity against Listeria monocytogenes

Listeria monocytogenes, a pathogenic bacterium causing zoonotic diseases, necessitates the urgent search for novel anti-Listeria monocytogenes drugs due to the continuous emergence of drug-resistant bacteria. In this study, we isolated and identified a bacteriocin-producing strain CM7-4 from seawater as Bacillus velezensis through 16S rRNA sequence analysis. Moreover, we successfully purified a novel bacteriocin named PCM7-4 from Bacillus velezensis CM7-4. The molecular weight of PCM7-4 was determined to be 40,228.99 Da. Notably, PCM7-4 exhibited broad-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria with a minimum inhibitory concentration (MIC) of 5.625 μg/mL against Listeria monocytogenes specifically. It demonstrated heat resistance and high stability within the pH range of 2-12 while being sensitive to proteinase K degradation without any observed hemolytic activity. Furthermore, SEM analysis revealed that PCM7-4 effectively inhibited biofilm formation and disrupted cell membranes in Listeria monocytogenes cells. Transcriptome analysis revealed that PCM7-4 exerts an impact on genes associated with crucial metabolic pathways, encompassing the biosynthesis of secondary metabolites, phosphotransferase systems (PTS), and starch/sucrose metabolism. These findings highlight the significant potential of bacteriocin PCM7-4 for the development of effective antimicrobial interventions targeting food-borne pathogenic bacteria.

Phenolic Compounds and Bacteriocins: Mechanisms, Interactions, and Applications in Food Preservation and Safety

Beneficial properties of different natural antimicrobials are topics of scientific curiosity for improving safety and extending the shelf life of food commodities. In this regard, phenolic compounds, natural molecules known for their antioxidant, anti-inflammatory, and antimicrobial properties can be right choice. Moreover, bacteriocins, antimicrobial peptides produced by various microorganisms, capable of inhibiting the growth of other bacteria, particularly closely related species can be genuine alternative. Combining phenolic compounds with bacteriocins can enhance antimicrobial effects, extending the shelf-life of food products by combating spoilage and foodborne pathogens. Despite their potential, the chemical interactions between phenolic compounds and bacteriocins, including synergistic and antagonistic effects, are not well understood. Key areas needing further research include the following: the mechanisms of action against different bacterium types, interactions with cell membranes, enzyme activity, and gene expression; the effects of environmental factors like concentration, pH, temperature, and food matrix specificity on their interactions; and methods for incorporating these compounds into food products and packaging materials to improve food safety. Additionally, the safety, toxicity, allergenicity, sensory properties, nutritional value, regulatory approval, and consumer acceptance of using phenolic compounds and bacteriocins in food products require thorough investigation.

Distinct phenotypes of salivaricin-producing Ligilactobacillus salivarius isolated from the gastrointestinal tract of broiler chickens and laying hens

Ligilactobacillus salivarius harbors bacteriocin genes in its repA-type megaplasmid, specifically salivaricin P (salP), a class IIb bacteriocin. This study aimed to differentiate 25 salP-positive Lig. salivarius strains isolated from the gastrointestinal tract (GIT) of broilers and laying hens. Results showed that 12 isolates were classified as Type A, with active bacteriocins, while the rest were Type B, with no active bacteriocins. In vitro and in silico characterization of salP bacteriocins revealed narrow-spectrum antibacterial activity against Listeria monocytogenes and Enterococcus faecalis. SalP bacteriocins were predicted as positively charged, hydrophobic, small molecular weight (α, 4.097 kDa; ß, 4.285 kDa) bacteriocins with characteristic GXXXG motif. Investigation of the salP gene cluster based on genomic data revealed that Type B strains lacked the lanT and hlyD genes that encode export proteins dedicated to the modification and extracellular transport of mature salP peptides. However, two Type B strains (B4311 and B5258) showed inhibitory activity against L. monocytogenes ATCC19114. Multiplex PCR analysis and synteny mapping analysis revealed that B4311 and B5258 strains harbored the lanT gene, highlighting the importance of LanT protein in the cleavage of leader peptide and excretion of mature peptides. Further analysis revealed that the resistance of Type B strains to salP was attributable to the presence of a dedicated immunity protein, blurring the evolutionary significance of producing active bacteriocins for competitive advantage. Additionally, the loss of export proteins occurred in a polyphyletic manner, consistent with the genetic plasticity of the repA-type megaplasmid. This suggests that the loss of lanT and hlyD is likely in the presence of limited nutritional competitors. In conclusion, the observed differences in salivaricin production of Lig. salivarius exist independent of isolation host and that Type A and Type B strains can coexist in the same environment. Finally, the functional characterization of active salP allows for a better understanding of its potential to control specific bacteria in human food and animal production.

Genomic insights into the probiotic potential and genes linked to gallic acid metabolism in Pediococcus pentosaceus MBBL6 isolated from healthy cow milk

Pediococcus pentosaceus is well known for its probiotic properties, including roles in improving health, antimicrobial production, and enhancing fermented food quality. This study aimed to comprehensively analyze the whole genome of P. pentosaceus MBBL6, isolated from healthy cow milk, to assess its probiotic and antimicrobial potentials. P. pentosaceus MBBL6, isolated from a healthy cow milk at BSMRAU dairy farm, Gazipur, Bangladesh, underwent comprehensive genomic analysis, including whole genome sequencing, assembly, annotation, phylogenetic comparison, and assessment of metabolic pathways and secondary metabolites. Antimicrobial efficacy was evaluated through in-vitro and in-vivo studies, alongside in-silico exploration for potential mastitis therapy. We predicted 1,906 genes and 204 SEED sub-systems involved in carbohydrate metabolism and vitamin B complex biosynthesis, with a focus on lactose metabolism in MMBL6. Notably, 43 putative carbohydrate-active enzyme genes, including lysozymes, suggest the ability of MBBL6 for carbohydrate biotransformation and antimicrobial activity. The genome also revealed primary metabolic pathways for arginine and gallic acid metabolism and secondary metabolite gene clusters, including T3PKS and RiPP-like regions. Importantly, two bacteriocin biosynthesis gene clusters namely bovicin_255_variant and penocin_A, were identified in MBBL6. The safety assessment of MBBL6 genome revealed no virulence genes and a low pathogenicity score (0.196 out of 1.0). Several genes related to survival in gastrointestinal tract and colonization were also identified. Furthermore, MBBL6 exhibited susceptibility to a wide range of antibiotics in-vitro, and effectively suppressed mastitis pathogens in an in-vivo mouse mastitis model trial. The observed bacteriocin, particularly bovicin, demonstrated the ability to disrupt the function of an essential protein, Rho factor of mastitis pathogens by blocking transcription termination process. Taken together, our in-depth genomic analysis underscores the metabolic versatility, safety profile, and antimicrobial potential of P. pentosaceus MBBL6, suggesting its promise for applications in therapeutics, bioremediation, and biopreservation.

Probiotic-Based Mineralized Living Materials to Produce Antimicrobial Yogurts

Mineralization of living cells represents an evolutionary adaptation that enhances cellular resilience to physicochemical stress. Inspired by this strategy, we have here developed hybrid living materials (HLMs), incorporating probiotics into mineralized collagen 3D matrices, with the aim of protecting and promoting the successful oral delivery of the bacteria. Collagen fibrils are simultaneously self-assembled and mineralized in the presence of the probiotics (Lactobacillus acidophilus, La, was used as model), resulting in the integration of the probiotics into the hybrid matrix (i.e., bulk encapsulation). During this process, probiotics are also coated with a nanofilm of apatite mineral (single-cell encapsulation), which provides them with extra protection and reinforces their viability and activity. In fact, the resulting HLM is metabolically active, and maintain the capacity to ferment milk into yogurt with antibacterial activity against the two major foodborne pathogens Pseudomonas aeruginosa (Pa) and Staphylococcus aureus (Sa). Interestingly, the HLM provides probiotics an additional protection in the gastrointestinal environment (i.e., simulated gastric fluid), which is of special interest for healthcare materials for oral administration. The results pave the way for the creation of innovative healthcare materials with enhanced functionalities and the potential to produce probiotic foods with notable antimicrobial properties.

A bacteriocin-based coating strategy to prevent vancomycin-resistant Enterococcus faecium biofilm formation on materials of interest for indwelling medical devices

The ever-increasing use of exogenous materials as indwelling medical devices in modern medicine offers to pathogens new ways to gain access to human body and begin, in some cases, life threatening infections. Biofouling of such materials with bacteria or fungi is a major concern during surgeries, since this is often associated with biofilm formation and difficult to treat, recalcitrant infections. Intense research efforts have therefore developed several strategies to shield the medical devices' surface from colonization by pathogenic microorganisms. Here, we used dopamine as a coupling agent to coat four different materials of medical interest (plastic polyetheretherketone (PEEK), stainless steel, titanium and silicone catheter) with the bacteriocins, enterocin EJ97-short and the thiopeptide micrococcin P1. Water contact angle measurements and x-ray photoelectron spectroscopy were used to verify the effective coating of the materials. The effect of bacteriocins coated on these materials on the biofilm formation by a vancomycin resistant Enterococcus faecium (VRE) strain was studied by biofilm-oriented antimicrobial test (BOAT) and electron scanning microscopy. The in vitro biocompatibility of bacteriocin-modified biomaterials was tested on cultured human cells. The results demonstrated that the binding of the bacteriocins to the implant surfaces is achieved, and the two bacteriocins in combination could inhibit biofilm formation by E. faecium on all four materials. The modified implant showed no cytotoxicity to the human cells tested. Therefore, surface modification with the two bacteriocins may offer a novel and effective way to prevent biofilm formation on a wide range of implant materials.

Marine Pediococcus pentosaceus E3 Probiotic Properties, Whole-Genome Sequence Analysis, and Safety Assessment

Probiotics play a significant role in enhancing health, and they are well known for bacteriocins production. Evaluating probiotics' whole-genome sequence provides insights into their consumption outcomes. Thus, genomic studies have a significant role in assessing the safety of probiotics more in-depth and offer valuable information regarding probiotics' functional diversity, metabolic pathways, and health-promoting mechanisms. Marine Pediococcus pentosaceus E3, isolated from shrimp gut, exhibited beneficial properties, indicating its potential as a probiotic candidate. Phenotypically, E3 strain was susceptible to most antibiotics assessed, tolerant to low pH and high bile salt conditions, and revealed no hemolysin activity. Interestingly, E3-neutralized CFS revealed significant antibacterial activity against pathogens under investigation. Therefore, the concentrated CFS was prepared and evaluated as a natural biopreservative and showed outstanding antimicrobial activity. Furthermore, integrated-based genome assessment has provided insight into probiotic characteristics at the genomic level. Whole-genome sequencing analysis revealed that the E3 genome possesses 1805 protein-coding genes, and the genome size was about 1.8 Mb with a G + C content of 37.28%. Moreover, the genome revealed the absence of virulence factors and clinically related antibiotic genes. Moreover, several genes consistent with probiotic microorganisms' features were estimated in the genome, including stress response, carbohydrate metabolism, and vitamin biosynthesis. In addition, several genes associated with survival and colonization within the gastrointestinal tract were also detected across the E3 genome. Therefore, the findings suggest that insights into the genetic characteristics of E3 guarantee the safety of the strain and facilitate future development of E3 isolate as a health-promoting probiotic and source of biopreservative.

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.

Genomic insights of Lactiplantibacillus plantarum CNPC024: a potential probiotic strain producing immune-boosting tryptophan-derived metabolites

Probiogenomics can provide important insights bout probiotic candidate bacteria. This study aimed to perform an in-depth genomic characterization of the probiotic candidate Lactiplantibacillus plantarum CNPC024 to investigate its probiosis mechanisms, identify metabolic pathways that might benefit the host, and improve the safety assessment for this strain to be effectively used as a probiotic. After whole-genome sequencing in Illumina MiSeq platform, the de novo genome assembly resulted in a 3.2 Mb draft genome. According to the Average Nucleotide Identity (ANI) analysis with 46 randomly validated probiotic LAB belonging to the Lactobacillaceae family, the strain showed a 99% nucleotide identity with other L. plantarum probiotic species. We identified a set of determinants conferring tolerance to bile salts and low pH conditions, as well as temperature, oxidative and osmotic stressors via the glutathione-glutaredoxin system (Grxs). As a β‑galactosidase‑producing strain, it has the potential to be used in fermented dairy products for lactose-intolerant individuals. There were no significant hits for transferable antibiotic-resistance genes. We also identified gene clusters associated with production of bacteriocins (plantaricins E, F and K). Lastly, we detected metabolic pathways associated with the production of tryptophan-derived metabolites that could potentially modulate the host's immune responses.

Mechanistic concepts involved in biofilm associated processes of Campylobacter jejuni: persistence and inhibition in poultry environments

Campylobacter species, predominantly Campylobacter jejuni, remains a significant zoonotic pathogen worldwide, with the poultry sector being the primary vector for human transmission. In recent years. there has been a notable rise in the incidence of human campylobacteriosis, necessitating a deeper understanding of the pathogen's survival mechanisms and transmission dynamics. Biofilm presence significantly contributes to C. jejuni persistence in poultry and subsequent food product contamination, and this review describes the intricate processes involved in biofilm formation. The ability of Campylobacter to form biofilms on various surfaces, including stainless steel, plastic, and glass, is a critical survival strategy. Campylobacter biofilms, with their remarkable resilience, protect the pathogen from environmental stresses such as desiccation, pH extremes, biocides and sanitizing agents. This review explores the molecular and genetic mechanisms of C. jejuni biofilm formation, highlighting regulatory genes involved in motility, chemotaxis, and stress responses. Flagellar proteins, particularly flaA, flaB, flaG, and adhesins like cadF and flpA, are identified as the main molecular components in biofilm development. The role of mixed-species biofilms, where C. jejuni integrates into existing biofilms of other bacteria to enhance pathogen resilience, is also discussed. This review also considers alternative interventions to control C. jejuni in poultry production, in the context of increasing antibiotic resistance. It explores the effectiveness of prebiotics, probiotics, synbiotics, bacteriocins, bacteriophages, vaccines, and organic acids, with a focus on their mechanisms of action in reducing bacterial colonization and biofilm formation. Studies show that mixtures of organic acids and compounds like Carvacrol and Eugenol significantly downregulate genes linked with motility and adhesion, thereby disrupting biofilm integrity. It discusses the impact of environmental factors, such as temperature and oxygen levels on biofilm formation, providing insights into how industrial conditions can be manipulated to reduce contamination. This paper stresses the need for a multifaceted approach to control Campylobacter in poultry, integrating molecular and genetic insights with practical interventions. By advancing our understanding of biofilm dynamics and gene regulation, we aim to inform the development of more effective strategies to enhance food safety and protect public health.

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 Critical Review of Postbiotics as Promising Novel Therapeutic Agents for Clostridial Infections

Clostridial infections, known for their severity and rapid progression, present significant challenges in both clinical and veterinary fields. These bacteria, which can survive without oxygen and produce protective spores, cause many diseases, ranging from simple gastrointestinal disorders to severe and potentially fatal infections including botulism, tetanus, and gas gangrene. The rising occurrence of antibiotic-resistant strains and the repetitive character of some Clostridial illnesses, including Clostridioides difficile infections (CDI), highlight the immediate need for alternate treatment approaches. Postbiotics, which are metabolites derived from probiotics, are showing great potential as effective agents against these diseases. The current study offers a comprehensive investigation of the potential of postbiotics as therapeutic agents for treating Clostridial infections, including C. difficile, Clostridium perfringens, Clostridium botulinum, and Clostridium tetani. It also examines the processes by which postbiotics exert their effects. Preliminary investigations have shown that postbiotics have promising antibacterial and antibiofilm properties, indicating their potential as adjunct agents in methods for controlling microbial growth. Nevertheless, more study is required to thoroughly demonstrate their medicinal uses.

Biopreservation strategies using bacteriocins to control meat spoilage and foodborne outbreaks

Fresh meat is highly perishable, presenting challenges in spoilage mitigation and waste reduction globally. Despite the efforts, foodborne outbreaks from meat consumption persist. Biopreservation offers a natural solution to extend shelf life by managing microbial communities. However, challenges include the effective diffusion of bacteriocins through the meat matrix and the potential inhibition of starter cultures by bacteriocins targeting closely related lactic acid bacteria (LAB). LAB, predominant in meat, produce bacteriocins - small, stable peptides with broad antimicrobial properties effective across varying pH and temperature conditions. This review highlights the recent advances in the optimization of bacteriocin use, considering its structure and mode of action. Moreover, the strengths and weaknesses of different techniques for bacteriocin screening, including novel bioengineering methods, are described. Finally, we discuss the advantages and limitations of the modes of application of bacteriocins toward the preservation of fresh, cured, and novel meat products.

Recent Advancements in Harnessing Lactic Acid Bacterial Metabolites for Fruits and Vegetables Preservation

Postharvest losses in fruits and vegetables exert substantial economic and environmental repercussions. Chemical interventions are being widely utilized for the past six decades which may lead to significant health complications. Bioprotection of fruits and vegetables is the need of the hour in which use of lactic acid bacteria (LAB) with GRAS status predominantly stands out. Incorporation of LAB in postharvest fruits and vegetables suppresses the growth of spoilage organisms by synthesizing various antimicrobial compounds such as bacteriocins, organic acids, hydrogen peroxide (H2O2), exopolysaccharides (EPS), and BLIS. For example, Pediococcus acidilactici, Lactobacillus plantarum, and Limosilactobacillus fermentum convert natural sugars in fruits and vegetables to lactic acid and create an acidic environment that do not favour spoilage organisms. LAB can improve the bioavailability of vitamins and minerals and enrich the phenolic profile and bioactivity components. LAB has remarkable physiological characteristics like resistance towards bacteriophage, proteolytic activity, and polysaccharide production which adds to the safety of foods. They modify the sensory properties and preserve the nutritional quality of fruits and vegetables. They can also perform therapeutic role in the intestinal tract as they tolerate low pH, high salt concentration. Thus application of LAB, whether independently or in conjunction with stabilizing agents as edible coatings, is regarded as an exceptionally promising methodology for ensuring safer consumption of fruits and vegetables. This review addresses the most recent research findings that harness the antagonistic property of lactic acid bacterial metabolites, formulations and coatings containing their bioactive compounds for extended shelf life of fruits and vegetables.

Impact of probiotics-derived extracellular vesicles on livestock gut barrier function

Probiotic extracellular vesicles (pEVs) are biologically active nanoparticle structures that can regulate the intestinal tract through direct or indirect mechanisms. They enhance the intestinal barrier function in livestock and poultry and help alleviate intestinal diseases. The specific effects of pEVs depend on their internal functional components, including nucleic acids, proteins, lipids, and other substances. This paper presents a narrative review of the impact of pEVs on the intestinal barrier across various segments of the intestinal tract, exploring their mechanisms of action while highlighting the limitations of current research. Investigating the mechanisms through which probiotics operate via pEVs could deepen our understanding and provide a theoretical foundation for their application in livestock production.

Purified L-glutaminase effects against multidrug-resistant Pseudomonas aeruginosa in experimental vaginosis model: An immunological and histopathological observation

The antimicrobial activity of crude and purified L-glutaminase (EC 3.5.1.2), obtained from Lactobacillus gasseri, was evaluated against multidrug-resistant Pseudomonas aeruginosa in the in vivo vaginosis condition. The L-glutaminase possessed significant antimicrobial and anti-biofilm formation activity against multi-drug resistance P. aeruginosa, which were confirmed in the BALBc rat vaginosis model, together with its effects on the immunological and histopathological aspects. The untreated animals showed heavy vaginitis, characterized by sub-epithelial edema and infiltration of mononuclear leukocytes, perivascular heavy inflammatory cells infiltration in the vaginal tissue, and moderate stromal edema. However, the L-glutaminase treatment exhibited no changes in vaginal tissue structure with normal appearance of the epithelium and lamina propria with marked repair of the vaginal section when compared with normal, uninfected, control group A. The immunomodulatory actions of the L-glutaminase were confirmed by observance of higher concentrations of tumor necrosis factor-γ (TNF-γ), and interleukin -12 (IL-12) in treated animals, while the interleukin-10 (IL-10) was higher in the infected, untreated animals' sera samples. Therefore, the L-glutaminase showed corrective and healing actions, which were observed through histopathological observations of the vaginal tissue. The investigations led to imply that L-glutaminase may have the potential to be an effective antimicrobial agent for preventing and inhibiting bacterial growth, as well as inhibiting the biofilm formation in the P. aeruginosa-originated vaginosis. The observations may be of promising value for future clinical use.

Mechanism of Cell-Killing Activity of Plantaricin LD1 Against Escherichia coli ATCC 25922

Plantaricin LD1 was purified from a potential probiotic strain, Lactobacillus plantarum LD1 previously isolated from indigenous food, Dosa. In this study, we have performed a detailed mechanism of action of plantaricin LD1 against Escherichia coli ATCC 25922 considering Micrococcus luteus MTCC 106 as control. The plantaricin LD1 showed a minimum inhibitory concentration (MIC) of 34.57 µg/mL and a minimum bactericidal concentration (MBC) of 138.3 µg/mL against M. luteus MTCC 106, whereas MIC 69.15 µg/mL and MBC 276.6 µg/mL were found against E. coli ATCC 25922. The efflux of potassium ions, dissipation of membrane potential (∆ψ), and transmembrane pH gradient (∆pH) of plantaricin LD1-treated cells suggested the membrane-acting nature of plantaricin LD1. Plantaricin LD1 also caused degradation of the genomic DNA of the target strains tested. The cell killing was confirmed by staining with propidium iodide and visualized under light and electron microscopes. The bacteriocin-treated cells were found to be ruptured, swollen, and elongated. Thus, the findings indicate plantaricin LD1 kills E. coli ATCC 25922 by interacting with the cell membrane resulting in the efflux of intracellular contents and also causing degradation of nucleic acids leading to cell death.

Food Waste Biotransformation into Food Ingredients: A Brief Overview of Challenges and Opportunities

In today's global context, challenges persist in preventing agri-food waste due to factors like limited consumer awareness and improper food-handling practices throughout the entire farm-to-fork continuum. Introducing a forward-thinking solution, the upcycling of renewable feedstock materials (i.e., agri-food waste and by-products) into value-added ingredients presents an opportunity for a more sustainable and circular food value chain. While multi-product cascade biorefining schemes show promise due to their greater techno-economic viability, several biotechnological hurdles remain to be overcome at many levels. This mini-review provides a succinct overview of the biotechnological and societal challenges requiring attention while highlighting valuable food-grade compounds derived from biotransformation processes. These bio-based ingredients include organic acids, phenolic compounds, bioactive peptides, and sugars and offer diverse applications as antioxidants, preservatives, flavorings, sweeteners, or prebiotics in foodstuffs and other consumer goods. Therefore, these upcycled products emerge as a sustainable alternative to certain potentially harmful artificial food additives that are still in use or have already been banned from the industry.

Antimicrobial Peptides Derived from Bacteria: Classification, Sources, and Mechanism of Action against Multidrug-Resistant Bacteria

Antimicrobial peptides (AMPs) are short, usually cationic peptides with an amphiphilic structure, which allows them to easily bind and interact with the cellular membranes of viruses, bacteria, fungi, and other pathogens. Bacterial AMPs, or bacteriocins, can be produced from Gram-negative and Gram-positive bacteria via ribosomal synthesis to eliminate competing organisms. Bacterial AMPs are vital in addressing the increasing antibiotic resistance of various pathogens, potentially serving as an alternative to ineffective antibiotics. Bacteriocins have a narrow spectrum of action, making them highly specific antibacterial compounds that target particular bacterial pathogens. This review covers the two main groups of bacteriocins produced by Gram-negative and Gram-positive bacteria, their modes of action, classification, sources of positive effects they can play on the human body, and their limitations and future perspectives as an alternative to antibiotics.

The Role of Lactic Acid Bacteria in Meat Products, Not Just as Starter Cultures

Lactic acid bacteria (LABs) are microorganisms of significant scientific and industrial importance and have great potential for application in meat and meat products. This comprehensive review addresses the main characteristics of LABs, their nutritional, functional, and technological benefits, and especially their importance not only as starter cultures. LABs produce several metabolites during their fermentation process, which include bioactive compounds, such as peptides with antimicrobial, antidiabetic, antihypertensive, and immunomodulatory properties. These metabolites present several benefits as health promoters but are also important from a technological point of view. For example, bacteriocins, organic acids, and other compounds are of great importance, whether from a sensory or product quality or a safety point of view. With the production of GABA, exopolysaccharides, antioxidants, and vitamins are beneficial metabolites that influence safety, technological processes, and even health-promoting consumer benefits. Despite the benefits, this review also highlights that some LABs may present virulence properties, requiring critical evaluation for using specific strains in food formulations. Overall, this review hopes to contribute to the scientific literature by increasing knowledge of the various benefits of LABs in meat and meat products.

Unlocking the potential of lactic acid bacteria mature biofilm extracts as antibiofilm agents

The continuous growth of biofilm infections and their resilience to conventional cleaning methods and antimicrobial agents pose a worldwide challenge across diverse sectors. This persistent medical, industrial, and environmental issue contributes to treatment challenges and chronic diseases. Lactic acid bacteria have garnered global attention for their substantial antimicrobial effects against pathogens and established beneficial roles. Notably, their biofilms are also predicted to show a promising control strategy against pathogenic biofilm formation. The prevalence of biofilm-related problems underscores the need for extensive research and innovative solutions to tackle this global challenge. This novel study investigates the effect of different extracts (external, internal, and mixed extracts) obtained from Lactobacillus rhamnosus GG biofilm on pathogenic-formed biofilms. Subsequently, external extracts presented an important eradication effectiveness. Furthermore, a 6-fold concentration of these extracts led to eradication percentages of 57%, 67%, and 76% for Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa biofilms, respectively, and around 99.9% bactericidal effect of biofilm cells was observed for the three strains. The results of this research could mark a significant breakthrough in the field of anti-biofilm and antimicrobial strategies. Further studies and molecular research will be necessary to detect the molecules secreted by the biofilm, and their mechanisms of action engaged in new anti-biofilm strategies.

Nanocomposites: silver nanoparticles and bacteriocins obtained from lactic acid bacteria against multidrug-resistant Escherichia coli and Staphylococcus aureus

Drug-resistant bacteria such as Escherichia coli and Staphylococcus aureus represent a global health problem that requires priority attention. Due to the current situation, there is an urgent need to develop new, more effective and safe antimicrobial agents. Biotechnological approaches can provide a possible alternative control through the production of new generation antimicrobial agents, such as silver nanoparticles (AgNPs) and bacteriocins. AgNPs stand out for their antimicrobial potential by employing several mechanisms of action that can act simultaneously on the target cell such as the production of reactive oxygen species and cell wall rupture. On the other hand, bacteriocins are natural peptides synthesized ribosomally that have antimicrobial activity and are produced, among others, by lactic acid bacteria (LAB), whose main mechanism of action is to produce pores at the level of the cell membrane of bacterial cells. However, these agents have disadvantages. Nanoparticles also have limitations such as the tendency to form aggregates, which decreases their antibacterial activity and possible cytotoxic effects, and bacteriocins have a narrow spectrum of action, require high doses to be effective, and can be degraded by proteases. Given these limitations, nanoconjugates of these two agents have been developed that can act synergistically in the control of pathogenic bacteria resistant to antibiotics. This review focuses on knowing relevant aspects of the antibiotic resistance of E. coli and S. aureus, the characteristics of these new generation antibacterial agents, and their effect alone or forming nanoconjugates that are more effective against the multiresistant mentioned bacteria.

Gut Distribution, Impact Factor, and Action Mechanism of Bacteriocin-Producing Beneficial Microbes as Promising Antimicrobial Agents in Gastrointestinal Infection

Gastrointestinal (GI) infection by intestinal pathogens poses great threats to human health, and the therapeutic use of antibiotics has reached a bottleneck due to drug resistance. The developments of antimicrobial peptides produced by beneficial bacteria have drawn attention by virtue of effective, safe, and not prone to developing resistance. Though bacteriocin as antimicrobial agent in gut infection has been intensively investigated and reviewed, reviews on that of bacteriocin-producing beneficial microbes are very rare. It is important to explicitly state the prospect of bacteriocin-producing microbes in prevention of gastrointestinal infection towards their application in host. This review discusses the potential of gut as an appropriate resource for mining targeted bacteriocin-producing microbes. Then, host-related factors affecting the bacteriocin production and activity of bacteriocin-producing microbes in the gut are summarized. Accordingly, the multiple mechanisms (direct inhibition and indirect inhibition) behind the preventive effects of bacteriocin-producing microbes on gut infection are discussed. Finally, we propose several targeted strategies for the manipulation of bacteriocin-producing beneficial microbes to improve their performance in antimicrobial outcomes. We anticipate an upcoming emergence of developments and applications of bacteriocin-producing beneficial microbes as antimicrobial agent in gut infection induced by pathogenic bacteria.

GLYCOCINS: The sugar peppered antimicrobials

Glycosylated bacteriocins, known as glycocins, were first discovered in 2011. These bioactive peptides are produced by bacteria to gain survival advantages. They exhibit diverse types of glycans and demonstrate varied antimicrobial activity. Currently, there are 13 experimentally known glycocins, with over 250 identified in silico across different bacterial phyla. Notably, glycocins are recognized for their glycan-mediated antimicrobial activity, proving effective against drug-resistant and foodborne pathogens. Many glycocins contain rare S-linked glycans. Glycosyltransferases (GTs), responsible for transferring sugar to glycocins and involved in glycocin biosynthesis, often cluster together in the producer's genome. This clustering makes them valuable for custom glycoengineering with diverse substrate specificities. Heterologous expression of glycocins has paved the way for the establishment of microbial factories for glycopeptide and glycoconjugate production across various industries. In this review, we emphasize the primary roles of fully and partially characterized glycocins and their glycosylating enzymes. Additionally, we explore how specific glycan structures facilitate these functions in antibacterial activities. Furthermore, we discuss newer approaches and increasing efforts aimed at exploiting bacterial glycobiology for the development of food preservatives and as replacements or complements to traditional antibiotics, particularly in the face of antibiotic-resistant pathogenic bacteria.

An insight into structure-activity relationships in subclass IIb bacteriocins: Plantaricin EvF

This study reports the structure-activity relationships of a unique subclass IIb bacteriocin, plantaricin EvF, which consists of two peptide chains and possesses potent antimicrobial activity. Because the plantaricin Ev peptide chain lacks an α-helix structure, plantaricin EvF is unable to exert its antimicrobial activity through helix-helix interactions like typical subclass IIb bacteriocins. We have shown by various structural evaluation methods that plantaricin Ev can be stabilized by hydrogen bonding at amino acid residues R3, V12, and R13 to the N-terminal region of plantaricin F. This binding gives plantaricin EvF a special spade-shaped structure that exerts antimicrobial activity. In addition, the root-mean-square deviations (RMSDs) of the amino acid residues Y6, F8, and R13 of plantaricin Ev pre- and post-binding were 1.512, 1.723, and 1.369, respectively, indicating that they underwent large structural changes. The alanine scanning experiments demonstrated the important role of the above key amino acids in maintaining the structural integrity of plantaricin EvF. This study not only reveals the unique structural features of plantaricin EvF, but also provides an insight into the structure-activity relationships of subclass IIb bacteriocins.

Lactococcus lactis MA5 is a potential autochthonous probiotic for nutrient digestibility enhancement and bacterial pathogen inhibition in hybrid catfish (Ictalurus punctatus × I. furcatus)

With the emergence of diseases, the U.S. catfish industry is under challenge. Current trends prefer autochthonous bacteria as potential probiotic candidates owing to their adaptability and capacity to effectively colonize the host's intestine, which can enhance production performance and bolster disease resistance. The objective of this study was to isolate an autochthonous bacterium as probiotic for hybrid catfish. Initially, an analysis of the intestinal microbiota of hybrid catfish reared in earthen ponds was conducted for subsequent probiotic development. Twenty lactic acid bacteria were isolated from the digesta of overperforming catfish, and most of the candidates demonstrated probiotic traits, including proteolytic and lipolytic abilities; antagonistic inhibition of catfish enteric bacterial pathogens, negative haemolytic activity and antibiotic susceptibility. Subsequent to this screening process, an isolate of Lactococcus lactis (MA5) was deemed the most promising probiotic candidate. In silico analyses were conducted, and several potential probiotic functions were predicted, including essential amino acids and vitamin synthesis. Moreover, genes for three bacteriocins, lactococcin A, enterolysin A and sactipeptide BmbF, were identified. Lastly, various protectant media for lyophilization of MA5 were assessed. These findings suggest that Lactococcus lactis MA5 can be an autochthonous probiotic from hybrid catfish, holding promise to be further tested in feeding trials.

Strategies for developing phages into novel antimicrobial tailocins

Tailocins are high-molecular-weight bacteriocins produced by bacteria to kill related environmental competitors by binding and puncturing their target. Tailocins are promising alternative antimicrobials, yet the diversity of naturally occurring tailocins is limited. The structural similarities between phage tails and tailocins advocate using phages as scaffolds for developing new tailocins. This article reviews three strategies for producing tailocins: disrupting the capsid-tail junction of phage particles, blocking capsid assembly during phage propagation, and creating headless phage particles synthetically. Particularly appealing is the production of tailocins through synthetic biology using phages with contractile tails as scaffolds to unlock the antimicrobial potential of tailocins.

Probiotic Lactobacillus rhamnosus species: considerations for female reproduction and offspring health

Lactobacillus rhamnosus is a type of bacteria known as a probiotic and is often used to support the health of the digestive system and vaginal flora. This type of bacteria has an important role, showing positive effects on female reproductive biology, particularly by maintaining the balance of microorganisms in the vagina, reducing the risk of infection, and strengthening the immune system to support maternal health during pregnancy. There are also studies showing that these probiotics prevent maternal obesity and gestational diabetes. Consuming probiotics containing Lactobacillus rhamnosus strains may support the intestinal health of breastfeeding mothers, but they may also contribute to the health of offspring. Therefore, this review focuses on the current available data for examining the effects of Lactobacillus rhamnosus strains on female reproductive biology and offspring health. A systematic search was conducted in the PubMed and Web of Science databases from inception to May 2024. The search strategy was performed using keywords and MeSH (Medical Subject Headings) terms. Inconsistent ratings were resolved through discussion. This review is strengthened by multiple aspects of the methodological approach. The systematic search strategy, conducted by two independent reviewers, enabled the identification and evaluation of all relevant literature. Although there is a limited number of studies with high heterogeneity, current literature highlights the important contribution of Lactobacillus rhamnosus probiotics in enhancing female reproductive health and fertility. Furthermore, the probiotic bacteria in breast milk may also support the intestinal health of newborn, strengthen the immune system, and protect them against diseases at later ages.

Appraisal of postbiotics in cancer therapy

Cancer remains a multifactorial disease with an increased mortality rate around the world for the past several decades. Despite advancements in treatment strategies, lower survival rates, drug-associated side effects, and drug resistance create a need for novel anticancer agents. Ample evidence shows that imbalances in the gut microbiota are associated with the formation of cancer and its progression. Altering the gut microbiota via probiotics and their metabolites has gained attention among the research community as an alternative therapy to treat cancer. Probiotics exhibit health benefits as well as modulate the immunological and cellular responses in the host. Apart from probiotics, their secreted products like bacteriocins, exopolysaccharides, short-chain fatty acids, conjugated linoleic acid, peptidoglycan, and other metabolites are found to possess anticancer activity. The beneficiary role of these postbiotic compounds is widely studied for characterizing their mechanism and mode of action that reduces cancer growth. The present review mainly focuses on the postbiotic components that are employed against cancer with their reported mechanism of action. It also describes recent research works carried out so far with specific strain and anticancer activity of derived compounds both in vitro and in vivo, validating that the probiotic approach would pave an alternative way to reduce the burden of cancer.

Synthesis, antimicrobial activity, and mechanistic studies of enterocin DD14, a leaderless two-peptide bacteriocin

Bacteriocins are promising alternatives to antibiotics in the food, veterinary and medical sectors, but their study and use is often hampered by the low yields and high costs associated with their purification from naturally occurring bacteria. Chemical synthesis has emerged as a means to overcome this limitation and design more active variants. In this study, microwave-assisted solid-phase peptide synthesis was used to produce the leaderless two-peptide bacteriocin enterocin DD14 (EntDD14), composed of EntDD14A (44 amino acids) and EntDD14B (43 amino acids). The resulting synthetic peptides, syn-EntDD14A and syn-EntDD14B, were tested against Gram-positive bacteria including Listeria, Staphylococcus and Enterococcus strains. Both peptides were found to be necessary for optimal, but not synergistic, antibacterial activity and to act through a pore-forming mechanism. Both peptides exhibited moderate cytotoxicity against eukaryotic cells.

Application of microbial enzymes in medicine and industry: current status and future perspectives

Microbes are a major source of enzymes due to their ability to be mass-cultivated and genetically modified. Compared with plant and animal enzymes, microbial enzymes are more stable and active. Enzymes are generally classified into six classes based on their reaction, substrate specificity and mechanism of action. In addition to their application in medicine for treating diseases, these compounds are used as anti-inflammatory, thrombolytic and digestive agents. However, challenges such as immunogenicity, tissue specificity and short in vivo half-life make clinical trials complex. Enzymes are metabolic catalysts in industry and their production and extraction must be optimized to preserve profitability due to rising demand. The present review highlights the increasing importance of bacterial enzymes in industry and medicine and explores methods for their production, extraction and purification.

A novel bacteriocin against methicillin-resistant Staphylococcus aureus, purified from Lactiplantibacillus plantarum ZFM9

A novel bacteriocin, plantaricin ZFM9, was purified from Lactiplantibacillus plantarum ZFM9 using a combination of ammonium sulfate precipitation, XAD-2 macroporous resin, Sephadex G-50, Sephadex LH-20, and reversed-phase high performance liquid chromatography. The molecular mass of plantaricin ZFM9 was 1151.606 Da, and the purity was 98.3%. Plantaricin ZFM9 has thermal stability (95.6% retention at 120 °C for 30 min), pH stability (pH ≤ 5), and sensitivity to the pepsin, trypsin, papain, and proteinase K. Plantaricin ZFM9 exhibited broad-spectrum antimicrobial activity and notably inhibit methicillin-resistant Staphylococcus aureus D48 (MRSA). According to the results of electron microscopy and fluorescence leakage assay, it was found that plantaricin ZFM9 caused damage to the cells membrane and leakage of the contents of S. aureus D48. In addition, Lipid II was not the anti-MRSA target of plantaricin ZFM9. This study underscores the potential of plantaricin ZFM9 for applications in the food field and biopharmaceuticals against MRSA infection.

Lactobacillus gasseri and Gardnerella vaginalis produce extracellular vesicles that contribute to the function of the vaginal microbiome and modulate host-Trichomonas vaginalis interactions

Trichomonas vaginalis is an extracellular protozoan parasite of the human urogenital tract, responsible for a prevalent sexually transmitted infection. Trichomoniasis is accompanied by a dysbiotic microbiome that is characterised by the depletion of host-protective commensals such as Lactobacillus gasseri, and the flourishing of a bacterial consortium that is comparable to the one seen for bacterial vaginosis, including the founder species Gardnerella vaginalis. These two vaginal bacteria are known to have opposite effects on T. vaginalis pathogenicity. Studies on extracellular vesicles (EVs) have been focused on the direction of a microbial producer (commensal or pathogen) to a host recipient, and largely in the context of the gut microbiome. Here, taking advantage of the simplicity of the human cervicovaginal microbiome, we determined the molecular cargo of EVs produced by L. gasseri and G. vaginalis and examined how these vesicles modulate the interaction of T. vaginalis and host cells. We show that these EVs carry a specific cargo of proteins, which functions can be attributed to the opposite roles that these bacteria play in the vaginal biome. Furthermore, these bacterial EVs are delivered to host and protozoan cells, modulating host-pathogen interactions in a way that mimics the opposite effects that these bacteria have on T. vaginalis pathogenicity. This is the first study to describe side-by-side the protein composition of EVs produced by two bacteria belonging to the opposite spectrum of a microbiome and to demonstrate that these vesicles modulate the pathogenicity of a protozoan parasite. Such as in trichomoniasis, infections and dysbiosis co-occur frequently resulting in significant co-morbidities. Therefore, studies like this provide the knowledge for the development of antimicrobial therapies that aim to clear the infection while restoring a healthy microbiome.

The effect of silver nanoparticles on the antimicrobial activity of cloned nisin against extensively drug-resistant Acinetobacter baumannii"

BACKGROUND

Antibiotic resistance is a global threat to human health that leads to disasters. Acinetobacter baumannii cannot be controlled by the existing antibiotics, and it became challenging. Therefore, novel antibacterial agents are required to combat such threats. The aim of this project is to find a novel antimicrobial agent to treat this multi-drug resistant bacterium.

METHODS

The NisA gene was isolated from Lactococcus lactis spp. lactis and cloned into the pET-3a plasmid using Gibson cloning assembly. Purified Nisin from cloning was conjugated with silver nanoparticles. Finally, an assessment of antibacterial activity for each of the purified Nisin, Silver nanoparticles, and Nisin-Silver nanoparticles conjugate against the extensively drug-resistant A. baumannii was performed.

RESULTS

Nisin was successfully purified from cloned bacteria, and the concentration was 416 µg/ml. The conjugation of nisin and silver nanoparticles was analyzed by electron microscopy. The minimum inhibitory concentration of Nisin and silver nanoparticles against A. baumannii were 104 µg/ml and 125 µg/ml, respectively. While Nisin-silver nanoparticle conjugates showed potent antimicrobial activity with MIC 125-52 µg/ml in which silver nanoparticles increased the antimicrobial activity of nisin beyond its optimum concentration (104 µg/ml). ‎ CONCLUSION: The development of new antibacterial agents is necessary to control extensively drug-resistant bacteria. Nisin-silver conjugates showed more potent antimicrobial activity than when applied separately and gave hope to combat the multi-drug resistant A. baumannii.

Subclass IId bacteriocins targeting mannose phosphotransferase system-Structural diversity and implications for receptor interaction and antimicrobial activity

The bacterial mannose phosphotransferase system (Man-PTS) mediates uptake of selected monosaccharides. Simultaneously, it is a receptor for diverse bacteriocins such as subclass IIa pediocin-like bacteriocins and some subclass IId ones (garvicins ABCQ, lactococcins ABZ, BacSJ, ubericin K, and angicin). So far, no attempt has been made to categorize this ever-expanding group of bacteriocins. Here, we identified Man-PTS as a receptor for a number of previously uncharacterized bacteriocins, and demonstrated that they all belong to a large family of Man-PTS-binding nonpediocin-like peptides, providing new insights into their structure and function. Based on amino acid sequence similarities between members of this family, we propose their classification into five groups. This classification conveniently distinguishes bacteriocins with specific structures and properties regarding their spectrum of antimicrobial activity and pattern of interaction with Man-PTS. With respect to the latter, we indicate individual amino acid residues or regions of Man-PTS and the bacteriocin responsible for their interaction. In Man-PTS, these residues localize to the exterior of the transport complex, specifically the extracellular loop of the so-called Vmotif domain-containing regions γ and/or γ+, and to the interior of the transport complex, specifically the interface between the Core and Vmotif domains. Finally, we propose that while the bacteriocins from separate groups display specific binding patterns to Man-PTS, the general mechanism of their interaction with the receptor is universal despite significant differences in their predicted structures, i.e. after initial docking on the bacterial cell through an interaction with the Man-PTS regions γ and/or γ+, they pull away its Core and Vmotif from one another to form a pore across the membrane.

Antimicrobial peptides: Opportunities and challenges in overcoming resistance

Antibiotic resistance represents a global health threat, challenging the efficacy of traditional antimicrobial agents and necessitating innovative approaches to combat infectious diseases. Among these alternatives, antimicrobial peptides have emerged as promising candidates against resistant pathogens. Unlike traditional antibiotics with only one target, these peptides can use different mechanisms to destroy bacteria, with low toxicity to mammalian cells compared to many conventional antibiotics. Antimicrobial peptides (AMPs) have encouraging antibacterial properties and are currently employed in the clinical treatment of pathogen infection, cancer, wound healing, cosmetics, or biotechnology. This review summarizes the mechanisms of antimicrobial peptides against bacteria, discusses the mechanisms of drug resistance, the limitations and challenges of AMPs in peptide drug applications for combating drug-resistant bacterial infections, and strategies to enhance their capabilities.

Antibacterial Activity and Cytotoxicity of the Novel Bacteriocin Pkmh

Bacteriocins are a class of proteins produced by bacteria that are toxic to other bacteria. These bacteriocins play a role in bacterial competition by helping to inhibit potential competitors. In this study, we isolated and purified a novel bacteriocin Pkmh, different from the previously reported bacteriocin PA166, from Pseudomonas sp. strain 166 by ammonium sulfate precipitation, dialysis membrane method, ion exchange chromatography, and gel filtration chromatography. SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) revealed that the molecular weight of Pkmh is approximately 35 kDa. Pkmh exhibited potent antimicrobial activity against bovine Mannheimia haemolytica (M. haemolytica) with low cytotoxicity, and lower hemolytic activity was observed. In addition, Pkmh retained antimicrobial activity at different pH ranges (2-10) and temperature conditions (40, 60, 80, 100 °C). Our analysis of its antimicrobial mechanism showed that Pkmh acts on bacterial cell membranes, increasing their permeability and leading to cell membrane rupture and death. In conclusion, Pkmh exhibited low hemolytic activity, low toxicity, and potent antibacterial effects, suggesting its potential as a promising candidate for clinical therapeutic drugs.

Bacillus spp. Isolated from Miang as Potential Probiotics in Nile Tilapia Culture-In Vitro Research

Among 79 Bacillus spp. isolated from Miang, a fermented tea in north Thailand, 17 Bacillus strains were selected with probiotic potential in Nile tilapia culture based on the capabilities of bacteriocin production and associated antimicrobial activities against fish pathogens, Aeromonas hydrophila and Streptococcus agalactiae. However, only six isolates were selected for further extensive studies based on the strength of their antimicrobial activities and their tolerance against simulated gastrointestinal conditions. The molecular identification by 16S rRNA gene sequence analysis revealed that five isolates, K2.1, K6.1, K7.1, K15.4, and K22.6, were Bacillus tequilensis, and the isolate K29.2 was Bacillus siamensis. B. siamensis K29.2 showed complete susceptibility to antibiotics tested in this study, while B. tequilensis K 15.4 showed moderate resistance to some antibiotics; therefore, both strains were selected as potential probiotic bacteria. B. tequilensis K15.4 and B. siamensis K29.2 were capable of the production and secretion of extracellular protease and polysaccharide degrading enzymes, including cellulase, xylanase, and β-mannanase. The tannin tolerant test also demonstrated their ability to grow on selective agar plates and secrete cellulase and β-mannanase in the presence of hydrolyzable tannin. In addition, in vitro digestion of commercial fish substrate revealed that the extracellular enzymes produced by both strains efficiently reacted with feed protein and polysaccharides. Based on the results from this study, B. siamensis K29.2 was deemed to have the highest potential multifunctional probiotic qualities for application in Nile tilapia culture, while the antibiotic-resistant gene in B. tequilensis K15.4 must be clarified before field application.

Microbial Contamination of Food: Probiotics and Postbiotics as Potential Biopreservatives

Microbial contamination of food and alimentary toxoinfection/intoxication in humans are commonly caused by bacteria such as Salmonella spp., Escherichia coli, Yersinia spp., Campylobacter spp., Listeria monocytogenes, and fungi (Aspergillus, Fusarium). The addition of probiotic cultures (bacterial strains Lactobacillus and Bifidobacterium and the yeast Saccharomyces cerevisiae var. boulardii) to food contributes primarily to food enrichment and obtaining a functional product, but also to food preservation. Reducing the number of viable pathogenic microorganisms and eliminating or neutralizing their toxins in food is achieved by probiotic-produced antimicrobial substances such as organic acids (lactic acid, acetic acid, propionic acid, phenylacetic acid, and phenyllactic acid), fatty acids (linoleic acid, butyric acid, caproic acid, and caprylic acid), aromatic compounds (diacetyl, acetaldehyde, reuterin), hydrogen peroxide, cyclic dipeptides, bacteriocins, and salivabactin. This review summarizes the basic facts on microbial contamination and preservation of food and the potential of different probiotic strains and their metabolites (postbiotics), including the mechanisms of their antimicrobial action against various foodborne pathogens. Literature data on this topic over the last three decades was searched in the PubMed, Scopus, and Google Scholar databases, systematically presented, and critically discussed, with particular attention to the advantages and disadvantages of using probiotics and postbiotics as food biopreservatives.