Bacteriocins: developing innate immunity for food

Searching for antibiotic-susceptible bioprotective lactic acid bacteria to control dangerous biological agents in artisanal cheese

Minas artisanal cheese (MAC) samples (n = 59) from 16 municipalities across five traditional MAC-producing regions in Brazil were used to prospect antibiotic-susceptible protective lactic acid bacteria (LAB) against three pathogenic bacteria found in the MAC. From 291 LAB isolates, 84 genetically diverse strains were selected via rep-PCR. MALDI-TOF identification revealed multiple species, predominantly Enterococcus faecalis (n = 37), Enterococcus faecium (n = 21), Lactiplantibacillus plantarum (n = 5) and Lacticaseibacillus rhamnosus (n = 3). The antagonistic activity of these strains was evaluated against Enterococcus faecalis ATCC 29212, Listeria monocytogenes ATCC 5779, and Escherichia coli O157:H7 using spot-on-lawn assays. Several strains showed strong inhibitory effects against E. coli and L. monocytogenes, with halo/colony ratios reaching 4.86 and 4.47, respectively. No antimicrobial peptide producing strain was observed. Antibiotic susceptibility was tested against nine antibiotics, and five strains were susceptible to all antibiotics, while 53 strains were susceptible to 5-8 antibiotics. However, five strains were resistant to all antibiotics, showing the highest resistance to gentamicin (66.7%), cotrimoxazole (58.3%), and streptomycin (57.2%). Resistance genes (aacA-aphD, ermA/B, tetM/O/K/L/S, blaZ, and vanA/B) were screened, and 40 strains harbored at least one gene. Taken together, these results revealed three antibiotic-susceptible bioprotective lactobacilli (L. rhamnosus 52, L. plantarum 177, and L. plantarum 272G) as superior strains, whose efficacy in eliminating E. coli O157 and Listeria monocytogenes in the milk matrix between 7- and 21-days post-inoculation was confirmed. These findings confirm the potential of these autochthonous lactobacilli to improve the safety of dairy, paving the way for their applications in product development in future projects.

Purification and characterization of a bacteriocin produced by the probiotic Lactiplantibacillus plantarum subsp. argentoratensis strain I1B

This study is aimed to characterize a broad-spectrum bacteriocin produced by Lactiplantibacillus plantarum subsp. argentoratensis strain I1B of fermented food origin and also to evaluate the in vitro probiotic properties of this strain. Cell supernatant of this strain showed broad-spectrum antibacterial activity against five prominent foodborne pathogens viz. Salmonella typhi 950, Escherichia coli 728, Yersinia enterocolitica 861, Listeria monocytogenes 657, and Klebsiella pneumoniae 618 with the strongest activity against the S. typhi 950. Cell supernatant also exhibited stability to proteolytic enzyme treatment, pH, and temperature. Optimum bacteriocin production was at 20-24 h of incubation in MRS broth at 37 °C with pH 6.0. The bacteriocin activity was retained in the 70% ammonium sulfate precipitate fraction, which was further purified using gel filtration chromatography (Sephadex G25 column) to the level of a single band on the SDS-PAGE and the activity was confirmed by zymogram. The molecular mass of the bacteriocin was found to be 22,199 Daltons. The pure molecule was identified using LC-MS/MS and was found to be an Adherence Protein with a sequence of chitin-binding domain consisting of 201 amino acid residues. The isolated strain exhibited potential probiotic activity within the established regulations and did not raise any possible safety concerns. This work reports a potent bacteriocin produced by a listed probiotic organism with latent postbiotic activity which could be used as a potential biopreservatives.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-025-04279-5.

A comprehensive review on nanochitosan and its diverse applications in various industries

Nanochitosan, a nanostructured form of chitosan produced from chitin, has become a widely used material with a wide range of applications in a variety of industries. This review summarizes the study on nanochitosan, including its synthesis techniques, distinct physicochemical characteristics, and uses in medicine, agriculture, cosmetics, and cleaning up the environment. The review also emphasizes the impact of synthesis methods such as nanoprecipitation, electrospinning, and chemical modifications on the material's properties and applications. In agriculture, nanochitosan can be used as a long-lasting biopolymer to support crop growth and health. Because it is mucoadhesive and compatible with living things, it can also enhance the effectiveness of medication. The potential of nanochitosan to enhance skin permeability and encapsulate active chemicals in cosmetics presents exciting opportunities for innovation. Furthermore, nanochitosan effectiveness as a biosorbent and antibacterial agent in wastewater treatment highlights its potential to tackle environmental issues. The present study offers valuable perspectives on the present status of nanochitosan research, highlights significant obstacles, and suggests future avenues for optimizing its industrial applications.

Identification and characterization of a novel bacteriocin produced by Lactiplantibacillus pentosus and the antibacterial mechanism on Listeria monocytogenes

In this study, bacteriocin L14 was isolated and identified from Lactiplantibacillus pentosus L14, which could effectively inhibit the growth of Listeria monocytogenes with 62.45 % of the inhibition rate at a concentration of 1 mg/mL. Bacteriocin L14 showed good stability and tolerance to temperature (37.48 % retention at 60 °C for 30 min), pH (2-10), proteases and UV radiation. According to the results of electron microscopy and fluorescence assay, bacteriocin L14 could disrupt the cell structure, reduce the intracellular ATP level, and lead to intracellular Ca2+ accumulation, phosphatidylserine exposure, DNA leakage and apoptosis. Transcriptomic analysis indicated that a total of 941 genes in L. monocytogenes showed significant alterations in expression with 404 genes significantly upregulated and 537 genes significantly downregulated in bacteriocin L14 treated cells. In L. monocytogenes, energy metabolism-associated genes (exemplified by fba) exhibited significant downregulation, leading to impaired cellular proliferation and diminished metabolic vigor. The downregulation of transport-associated genes (exemplified by cbiM) also resulted in diminished metabolic activity of L. monocytogenes. The downregulation of genes in ribosomes caused the abnormal synthesis of peptides. In conclusion, this study showed that bacteriocin L14 had the potential to be used as an antibacterial agent in food industry and control foodborne pathogens.

Characterisation of Enterocins Produced by Antilisterial Enterococcus faeciumBH04, BH12, BH84, and BH99 and In Vitro/In Situ Inhibition of Listeria monocytogenes

Listeria monocytogenes is a food pathogen that can cause fatal infections, especially in newborns, elderly individuals, and immunocompromised individuals. In recent years, research on novel antibiotics and natural antimicrobial agents of plant or microbial origin has become increasingly important in the face of multiple antibiotic resistance. In this study, enterocins produced by Enterococcus faecium BH04, BH12, BH84, and BH99 were investigated in vitro and in situ as antilisterial agents. The results showed that all strains had bacteriocin activity of 0.4 kAU/mL (400 AU/mL) after 3 h and 25.6 kAU/mL (25600 AU/mL) after 6 h in M17 broth. The strains inhibited the growth of Listeria monocytogenes ATCC 7644 in BHI. Furthermore, E. faecium BH04, BH12, BH84, and BH99 had bacteriostatic potential, whereas enterocins BH04, BH12, BH84, and BH99 had bactericidal potential in a milk model (in situ). The polymerase chain reaction results revealed that all strains had entA, entB, and entP genes encoding enterocin but not the entL50 gene. The enterocins BH04, BH12, BH84, and BH99 retained their antilisterial activity up to 100°C (10 min), up to pH 10, and against catalase, lysozyme, and all chemicals used in this study. On the other hand, ultraviolet light reduced the antilisterial activity of enterocin BH12 by 75% and that of enterocin BH04, BH84, and BH99 by 50%. It was concluded that E. faecium BH04, BH12, BH84, and BH99 could be used as a co-culture in fermented products and that enterocins produced by the strains could be used as antilisterial agents.

Stationary-Phase Antimicrobial Peptide Production in Escherichia coli

Antimicrobial peptides (AMPs) are a class of naturally occurring molecules found in animals, plants, and microorganisms. Ω76 is an AMP specifically designed for treating Carbapenem-resistant Enterobacteriaceae (CRE). Escherichia coli, engineered to produce Ω76, may serve as a potential whole-cell drug delivery system for treating CRE, yet Ω76 exhibited potent antimicrobial activity against the production host. In this study, PAtxA, a tightly controlled, high-level, modulable, and stationary-phase-specific promoter, was employed for the functional expression of Ω76 in E. coli. PAtxA facilitates the decoupling of bacterial growth from Ω76 production, enabling efficient Ω76 expression. The results show that PAtxA-governed Ω76 expression exhibited a relatively high OD600 and biomass concentration. In contrast, PT7-goverend Ω76 expression, which occurred during the log phase, showed a lower OD600 and dormancy with cell size reducing to less than 1 μm. The expression of Ω76 was confirmed in SDS-PAGE. The extraction of Ω76 was demonstrated using methanol and ethanol as solvents, while acetate and acetonitrile were found to be ineffective. The bacteria extract containing Ω76 exhibited antimicrobial activity against both Gram-negative E. coli and Gram-positive B. subtilis. Moreover, pTOL03F-Ω76 had a Ω76 concentration of 25 ± 3 mg/L compared to 21 ± 3 mg/L for pT7-Ω76. The solid antibacterial testing suggests the formation of Ω76 tertiary structures, indicating that conventional assays designed for small-molecule antibiotics may not be suitable for AMP assays. This study first reveals the phenotypic differences between log-phase and stationary-phase Ω76 expression, suggesting two potential applications for the stationary-phase promoter: (1) the development of a whole-cell drug delivery system, where the recombinant E. coli could grow along with CRE and produce Ω76 during the stationary phase to suppress CRE, and (2) its use in the production of secondary metabolites.

Antibacterial Effects of Synthetic Plantaricins Against Staphylococcus aureus

Background/Objectives: Plantaricins without a signal sequence were synthesized based on bacteriocins, plantaricins A, E, F, J, and K, of Lactiplantibacillus plantarum KM2. The antibacterial activities of four combinations of synthetic plantaricins-spPlnA, E&F, E&J, and J&K-were identified against Staphylococcus aureus ATCC 12692. And in this experiment, we aimed to identify the antimicrobial mechanism of the synthesized plantaricin sample against S. aureus. Methods/Results: The minimal inhibitory concentrations for each combination were 1.4 μg/mL, 1.8 μg/mL, 1.6 μg/mL, and 1.6 μg/mL, respectively. Raman spectra changed after treating S. aureus ATCC 12692 with synthetic plantaricins. Furthermore, transmission electron microscopy results revealed that the four synthetic plantaricin combinations could induce the cell lysis of S. aureus ATCC 12692. Finally, the four synthetic plantaricin combinations maintained their antibacterial effect at temperatures below 40 °C, and at pH levels of pH = (4-7). Except for spPlnJ&K, they are stable against the action of α-amylase and lysozyme. Overall, these results indicate that, excepting spPlnJ&K, the three synthetic plantaricin combinations exhibit similar antibacterial activity. Conclusions: Through this study, we confirmed that synthetic plantaricin exhibited antimicrobial activity against S. aureus, demonstrating its potential as a direct antimicrobial agent. However, since the antimicrobial activity decreased due to protease, it was confirmed that its use is limited in environments where protease is present.

A Review on Recent Trends in Bacteriophages for Post-Harvest Food Decontamination

Infectious diseases resulting from unsafe food consumption are a global concern. Despite recent advances and control measures in the food industry aimed at fulfilling the growing consumer demand for high-quality and safe food products, infection outbreaks continue to occur. This review stands out by providing an overview of post-harvest food decontamination methods against some of the most important bacterial foodborne pathogens, with particular focus on the advantages and challenges of using phages, including their most recent post-harvest applications directly to food and integration into active food packaging systems, highlighting their potential in providing safer and healthier food products. The already approved commercial phage products and the numerous available studies demonstrate their antibacterial efficacy against some of the most problematic foodborne pathogens in different food products, reinforcing their possible use in the future as a current practice in the food industry for food decontamination. Moreover, the incorporation of phages into packaging materials holds particular promise, providing protection against harsh conditions and enabling their controlled and continuous release into the food matrix. The effectiveness of phage-added packaging materials in reducing the growth of pathogens in food systems has been well-demonstrated. However, there are still some challenges associated with the development of phage-based packaging systems that need to be addressed with future research.

Heterologous Expression of Bacteriocins from the Metagenome Mining of Cotija Cheese

Bacteriocins are a heterologous group of ribosomal peptides with antibacterial activity. They are of interest to the pharmaceutical and food industries due to their potential to fight antibiotic-resistant pathogens and improve microbial food safety, respectively. Metagenomic data mining for antibacterial activity is valuable for the information it provides from unstudied genomic sequences. Furthermore, the higher biosynthetic yield obtained by the heterologous expression of putative bacteriocins allows their subsequent purification and characterization. This work aimed to express antilisterial bacteriocins in Escherichia coli after obtaining their gene sequences by in silico mining the bacterial metagenome of Cotija cheese. This artisanal Mexican cheese is manufactured with unpasteurized milk and ripens for at least 3 months. Analyzing the Cotija cheese bacterial shotgun metagenome allowed us to select two sequences (QC1 and QC2) encoding novel Class IId bacteriocins belonging to the lactococcin family. These genes were expressed as (His)6-fusion proteins in E. coli BL21 (DE3) and showed high antimicrobial activity against Listeria monocytogenes, with a minimum inhibitory concentration of 78 µg/mL. QC1 and QC2 were tested against several pathogenic bacteria and showed activity exclusively against L. monocytogenes. QC2 has a novel sequence that showed no matches against the UniProt database. It was purified by Ni2+ affinity chromatography and retained its activity after heating at 70 °C for 30 min. As the sequences were obtained by genomic mining on a fermented food metagenome, QC1 and QC2 have potential applications as sanitizers in industrial food facilities where L. monocytogenes contamination is the most prevalent.

Isolation and Characterization of Enterocin-Producing Enterococcus faecium Strains from Algerian Traditional Food "Dried Figs Marinated in Olive Oil": Functional and Safety Evaluations

The increasing consumer demand for natural and sustainable food preservation methods has highlighted the potential of lactic acid bacteria (LAB) and their bioactive metabolites, particularly bacteriocins, as effective antimicrobial agents. This study aimed to isolate and characterize Enterococcus faecium strains from Algerian traditional dried figs marinated in olive oil, a nutrient-dense and underexplored food matrix. Twelve isolates were identified as E. faecium using MALDI-TOF MS and 16S rRNA gene sequencing, ensuring precise taxonomic classification. Genotypic analyses (BOX-PCR, GTG-PCR, and ERIC-PCR) revealed substantial genetic diversity, with BOX-PCR demonstrating superior discriminatory power. Functional screening confirmed the presence of enterocin genes, including entA (100% of strains), entB (60%), and entL50A/B (20%), which correlated with inhibition zones against Enterococcus faecium VCY, Micrococcus luteus GPE 3001, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, and Acinetobacter lwoffii GPE 3002. Genotype-phenotype correlation analysis identified strain HFM7 as the most potent antimicrobial strain, exhibiting the largest inhibition zone (20.0 ± 1.0 mm) and harboring three enterocin genes (entA, entL50A, and entL50B). Protease sensitivity confirmed the proteinaceous nature of the antimicrobial compounds. Importantly, no virulence factors (esp, gelE, and hyl) or antibiotic resistance genes (vanA, vanB, ermA, ermB, and aac(6')-Ie-alph(2″)) were detected, underscoring the safety of these isolates for food applications. These findings suggest that E. faecium strains from traditional foods are promising candidates as natural biopreservatives and starter cultures in clean-label food systems. By bridging traditional food ecosystems and modern biotechnological advancements, this study provides a foundation for sustainable, minimally processed food preservation strategies with potential applications in enhancing food safety and shelf life.

Behaviour of Listeria monocytogenes and Yersinia enterocolitica during beef dry-aging up to 60 days

The Commission delegated Regulation (EU) 2024/1141 states that beef dry aging can be performed in a dedicated cabinet, at a surface temperature of -0.5 to 3 °C, maximum relative humidity of 85 %, air speed of 0.2-0.5 m/s and for a maximum of 35 days. Food business operators can apply different process parameters, even longer aging times, as long as they demonstrate to the competent authority that the aged meat is microbiologically safe. To support food business operators in the implementation of longer dry aging processes, in this study we investigated the behaviour of Listeria monocytogenes and Yersinia enterocolitica during beef dry aging in a patented cabinet up to 60 days. Beef loins were experimentally spiked with a mean load of 4.4 and 3.9 Log10 CFU/g of Listeria monocytogenes and Yersinia enterocolitica respectively and stored at 1 °C, relative humidity 78 % and ventilation 2.0 m/s for 60 days. L. monocytogenes counts did not significantly change during the dry aging process, while Y. enterocolitica significantly increased up to 3 Log10 CFU/g during the aging process and then tended to decrease at 60 days. The results of this study showed that beef dry aging at 1 ± 2 °C, relative humidity 78 ± 7 %, ventilation 2.0 m/s for 60 days does not support the growth of L. monocytogenes. On the contrary, the same process supported the growth of Y. enterocolitica up to 40 days in two of the three tested batches, showing that the impact of dry aging on the behaviour of this pathogen deserves further studies.

Exploring the Multifaceted Therapeutic Potential of Probiotics: A Review of Current Insights and Applications

The interplay between human health and the microbiome has gained extensive attention, with probiotics emerging as pivotal therapeutic agents due to their vast potential in treating various health issues. As significant modulators of the gut microbiota, probiotics are crucial in maintaining intestinal homeostasis and enhancing the synthesis of short-chain fatty acids. Despite extensive research over the past decades, there remains an urgent need for a comprehensive and detailed review that encapsulates probiotics' latest insights and applications. This review focusses on the multifaceted roles of probiotics in promoting health and preventing disease, highlighting the complex mechanisms through which these beneficial bacteria influence both gut flora and the human body at large. This paper also explores probiotics' neurological and gastrointestinal applications, focussing on their significant impact on the gut-brain axis and their therapeutic potential in a broad spectrum of pathological conditions. Current innovations in probiotic formulations, mainly focusing on integrating genomics and biotechnological advancements, have also been comprehensively discussed herein. This paper also critically examines the regulatory landscape that governs probiotic use, ensuring safety and efficacy in clinical and dietary settings. By presenting a comprehensive overview of recent studies and emerging trends, this review aims to illuminate probiotics' extensive therapeutic capabilities, leading to future research and clinical applications. However, besides extensive research, further advanced explorations into probiotic interactions and mechanisms will be essential for developing more targeted and effective therapeutic strategies, potentially revolutionizing health care practices for consumers.

Identification and characterization of a circular bacteriocin, garvicin SC, a novel garvicin ML variant, produced by Lactococcus garvieae ABG0038

We have identified and characterized a circular bacteriocin, termed garvicin SC (GarSC), produced by Lactococcus garvieae ABG0038 isolated from pine cones. Genome analysis of L. garvieae ABG0038 revealed that GarSC was a variant of the circular bacteriocin, garvicin ML (GarML), caused by an amino acid substitution, and predicted that GarSC was produced through a biosynthetic mechanism very similar to that of GarML. The two circular bacteriocins were purified and characterized for activity, and several differences were observed in pH stability, enzyme sensitivity, and antimicrobial activity. In particular, GarSC showed excellent stability in the basic pH range, which might extend the range of garvicin's application to one broader than that of GarML.

Production and transformation of biogenic amines in different food products by the metabolic activity of the lactic acid bacteria

Protein-rich diets often contain high quantities of biogenic amines (BAs), notably histamine and tyramine, which pose substantial health hazards owing to their toxicity. BAs are primarily produced by the microbial decarboxylation of free amino acids. Lactic acid bacteria (LAB) can either produce BAs using substrate-specific decarboxylase enzymes or degrade them into non-toxic compounds using amine-degrading enzymes such as amine oxidase and multicopper oxidase. Furthermore, LAB may inhibit BA-producing microbes by generating bioactive metabolites, including organic acids and bacteriocins. This paper thoroughly explores the processes underlying BA production and degradation in LAB, with a focus on the diversity of enzymes involved. Metabolic mapping of LAB strains at the genus and species levels reveals their involvement in BA metabolism, from production to degradation. The phylogenetic-based evolutionary relatedness of BA-producing and BA-degrading enzymes among LAB strains sheds light on their functional adaptability to various metabolic needs and ecological settings. These findings have significant practical implications for establishing better microbial management strategies in food production, particularly through strategically using starter or bioprotective cultures to reduce BA buildup. By highlighting the evolutionary and metabolic diversity of LAB, this review helps to optimize industrial fermentation processes, improve food safety protocols, and advance future research and innovation in BA management, ultimately protecting consumer health and supporting regulatory compliance.

Bacteriocin-Producing Enterococci Modulate Cheese Microbial Diversity

Cheese production involves various lactic acid bacteria (LAB) that break down lactose, milk proteins, and fats, producing key nutrients and influencing the cheese's flavor. They form communities that play a crucial role in determining the cheese's organoleptic properties. The composition of cheeses' microbial communities is shaped by physicochemical factors (e.g., temperature, pH, and salinity) and biological factors (i.e. microbial interactions). While starter cultures are introduced to control these communities, non-starter LAB represent a significant portion of the final microbial assemblage, but their interactions remain unclear. LAB often produce bacteriocins, antimicrobial peptides that antagonize other bacteria, but their role within LAB communities is not fully understood. This study aimed to assess the impact of bacteriocin production on LAB diversity in cheese, using Enterococcus as a model organism, a common bacteriocin producer. We analyzed enterocin production of enterococcal isolates by antimicrobial assays and microbial diversity differences in raw milk cheeses by two approaches: 16S RNA gene amplicon metagenomic sequencing for the whole microbial community and multi-locus sequence analysis (MLSA) for the enterococcal diversity. Our results revealed that LAB communities were dominated by lactococci, lactobacilli, and streptococci, with enterococci present in lower numbers. However, cheeses containing bacteriocin-producing enterococci exhibited higher microbial diversity. Interestingly, the highest diversity occurred at low levels of bacteriocin producers, but this effect was not observed within enterococcal populations. These findings suggest that bacteriocin production plays a key role in shaping LAB communities during cheese ripening, although further research is needed to understand its broader implications in other microbial ecosystems.

Isolation of New Strains of Lactic Acid Bacteria from the Vaginal Microbiome of Postmenopausal Women and their Probiotic Characteristics

Lactic acid bacteria (LAB), traditionally consumed as fermented foods, are now being applied to the medical field beyond health-functional food as probiotics. Therefore, it is necessary to continuously discover and evaluate new strains with suitable probiotic characteristics, mainly focusing on safety. In this study, we isolated eight new strains from postmenopausal vaginal fluid using culturomics approaches, an emerging area of interest. Data showed that most strains possessed significant cell surface hydrophobicity (≥ 76%), auto-aggregation capacity (17 to 61%), strong adhesion activity (8 to 34%), and excellent resistance to gastric acid, bile salt, and digestive enzyme, enhancing their survival in the gastrointestinal tract. Moreover, the strains exhibited functional characteristics, including substantial antibacterial activity with a minimal inhibitory concentration (MIC) ranging from 12.5 to 50%. They also harbored bacteriocins genes, produced short-chain fatty acids (acetate and propionate), exhibited significant phagocytic activity, possessed high antioxidative properties, rapidly depleted sodium nitrite, and exhibited proteolysis and β-glucosidase activity. In addition, heat-killed LAB strains significantly reduced the gene expressions of proinflammatory cytokines such as IL-β, IL-6, and iNOS in macrophages. Safety assessment revealed no cytotoxicity in macrophage cell lines. All strains tested negative for biogenic amine or H2O2 production, displayed no gelatinase or hemolytic activity, lacked virulence genes or detrimental enzymes, and displayed antibiotic susceptibility. In summary, these newly isolated strains demonstrate excellent probiotic functionality with a strong focus on safety, making them promising candidates for future drug development in the relevant fields.

The Genetic Determinants of Listeria monocytogenes Resistance to Bacteriocins Produced by Lactic Acid Bacteria

BACKGROUND

Listeria monocytogenes is a Gram-positive bacterium responsible for listeriosis, a serious foodborne disease that can lead to serious health complications. Pregnant women, newborns, the elderly, and patients with weakened immune systems are particularly susceptible to infection. Due to the ability of L. monocytogenes to survive in extreme environmental conditions, such as low temperatures, high salinity, and acidity, this bacterium poses a serious threat to food production plants and is particularly difficult to eliminate from these plants. One of the promising solutions to reduce the presence of this bacterium in food products is bacteriocins as natural control agents. These are substances with antibacterial activity produced by other bacteria, mainly lactic acid bacteria (LAB), which can effectively inhibit the development of pathogens such as L. monocytogenes. The use of bacteriocins in the food industry is beneficial due to their natural origin, specificity of action, and consumer safety. However, the problem of resistance to these substances exists.

RESULTS

This review focuses on the mechanisms of bacteriocin resistance, such as modifications of bacteriocin docking receptors, changes in the structure of the cell wall and membrane, and the occurrence of cross-resistance to different bacteriocins. Genetic factors determining these mechanisms and strategies to cope with the problem of resistance are also presented.

CONCLUSIONS

Research on this issue is crucial for developing effective preventive methods that will enable the safe and long-term use of bacteriocins in food production.

Health benefits, antimicrobial activities, and potential applications of probiotics: A review

Gut microbiota and its metabolic activities can influence the physiology and pathology of the human body. It is well established that alterations in the balance of living microbiota can contribute to various health problems, such as inflammatory bowel disease and autoimmune disorders. Probiotics administered in sufficient quantities as functional food ingredients provide health benefits to hosts. They help to maintain the stability and composition of the gut microbiota and provide resistance to infection by pathogens. The most important probiotic bacteria are Lactobacillus spp. and Bifidobacteria spp., which protect the intestine through various mechanisms such as the production of organic acids and bacteriocins. Scientific and clinical research has demonstrated that probiotics play a role in modulating immune response and preventing cancer and chronic inflammatory diseases, especially in the gastrointestinal tract. This article summarizes the potential health benefits, antimicrobial activities, and purposes for which probiotics can be used as functional foods to improve human health.

Nutrition of Escherichia coli within the intestinal microbiome

In this chapter, we update our 2004 review of "The Life of Commensal Escherichia coli in the Mammalian Intestine" (https://doi.org/10.1128/ecosalplus.8.3.1.2), with a change of title that reflects the current focus on "Nutrition of E. coli within the Intestinal Microbiome." The earlier part of the previous two decades saw incremental improvements in understanding the carbon and energy sources that E. coli and Salmonella use to support intestinal colonization. Along with these investigations of electron donors came a better understanding of the electron acceptors that support the respiration of these facultative anaerobes in the gastrointestinal tract. Hundreds of recent papers add to what was known about the nutrition of commensal and pathogenic enteric bacteria. The fact that each biotype or pathotype grows on a different subset of the available nutrients suggested a mechanism for succession of commensal colonizers and invasion by enteric pathogens. Competition for nutrients in the intestine has also come to be recognized as one basis for colonization resistance, in which colonized strain(s) prevent colonization by a challenger. In the past decade, detailed investigations of fiber- and mucin-degrading anaerobes added greatly to our understanding of how complex polysaccharides support the hundreds of intestinal microbiome species. It is now clear that facultative anaerobes, which usually cannot degrade complex polysaccharides, live in symbiosis with the anaerobic degraders. This concept led to the "restaurant hypothesis," which emphasizes that facultative bacteria, such as E. coli, colonize the intestine as members of mixed biofilms and obtain the sugars they need for growth locally through cross-feeding from polysaccharide-degrading anaerobes. Each restaurant represents an intestinal niche. Competition for those niches determines whether or not invaders are able to overcome colonization resistance and become established. Topics centered on the nutritional basis of intestinal colonization and gastrointestinal health are explored here in detail.

Screening and Genomic Profiling of Antimicrobial Bacteria Sourced from Poultry Slaughterhouse Effluents: Bacteriocin Production and Safety Evaluation

Background/Objectives: Antimicrobial-resistant (AMR) pathogens represent a serious threat to public health, particularly in food production systems where antibiotic use remains widespread. As a result, alternative antimicrobial treatments to antibiotics are essential for effectively managing bacterial infections. This study aimed to identify and characterize novel antimicrobial peptides produced by bacteria, known as bacteriocins, as well as to recognize safe bacteriocin-producing strains, sourced from poultry slaughterhouse effluents. Methods: A total of 864 bacterial isolates were collected across eight stages of a poultry slaughter line and screened for antimicrobial activity against Gram-positive and Gram-negative indicator strains. Whole-genome sequencing (WGS) was performed on 12 selected strains, including Enterococcus faecium (6 isolates), Lactococcus lactis (1 isolate), Lactococcus garvieae (1 isolate) and Escherichia coli (4 isolates). The presence of bacteriocin gene clusters (BGC), antibiotic resistance genes (ARG), and virulence factors (VF) was analyzed. The antimicrobial activity of a novel bacteriocin was further evaluated using in vitro cell-free protein synthesis (IV-CFPS). Results: WGS revealed multiple BGCs, including a novel class IId bacteriocin, lactococcin P1A (LcnP1A), in L. lactis SWD9. LcnP1A showed antimicrobial activity against various indicator strains, including Listeria monocytogenes. While most bacteriocin-encoding strains harbored ARGs and VFs, E. faecium SWG6 was notable for its absence of ARGs and minimal VFs, highlighting its potential as a probiotic. Conclusions: These findings underscore the importance of discovering novel bacteriocins and safer bacteriocin producing strains to address antimicrobial resistance in the food chain. Further research would validate the efficacy of both the novel lactococcin P1A bacteriocin and the E. faecium SWG6 isolate for application in processed food and animal production systems.

A Comprehensive Review on Bioactive Molecules and Advanced Microorganism Management Technologies

The advent of new strains of resistant microbes and the concomitant growth in multidrug resistance have made antimicrobial resistance an urgent public health concern. New antimicrobials are desperately needed to boost the success rates of treating infectious diseases and save lives. There are many intriguing biomolecules with antibacterial action, which are mostly unexplored in microorganisms. This review article describes the importance of natural compounds against microorganisms using advanced techniques to protect individuals from diseases. We have conducted an extensive literature review using databases such as SCOPUS, SCI, PUBMED, ScienceDirect, and Medline to gather relevant information. Our review covers various microorganism sources for antimicrobials, antifungal drugs, micro-culturing techniques, and microbial-based microsystems' applications. Every kind of higher trophic life depends on microorganisms for sustenance. The unseen majority is essential to understanding how humans and other living forms can survive anthropogenic climate change. The article discusses antimicrobial substances and the latest techniques and strategies for developing effective treatments. Novel model systems and cutting-edge biomolecular and computational methodologies could help researchers enhance antimicrobial resistance by completely capitalizing on lead antimicrobials.

Isolation, Genomics-Based and Biochemical Characterization of Bacteriocinogenic Bacteria and Their Bacteriocins, Sourced from the Gastrointestinal Tract of Meat-Producing Pigs

Antimicrobial resistance (AMR) poses a significant challenge to animal production due to the widespread use of antibiotics. Therefore, there is an urgent need for alternative antimicrobial strategies to effectively manage bacterial infections, protect animal health, and reduce reliance on antibiotics. This study evaluated the use of emerging approaches and procedures for the isolation, identification, and characterization of bacteriocin-producing bacteria and their bacteriocins, sourced from the gastrointestinal tract (GIT) of meat-producing pigs. Out of 2056 isolates screened against Gram-positive and Gram-negative indicator strains, 20 of the most active antimicrobial isolates were subjected to whole genome sequencing (WGS) for the prediction of coding DNA sequences (CDS) and the identification of bacteriocin gene clusters (BGC) and their functions. The use of an in vitro cell-free protein synthesis (IV-CFPS) protocol and the design of an IV-CFPS coupled to a split-intein mediated ligation (IV-CFPS/SIML) procedure made possible the evaluation of the production and antimicrobial activity of described and putatively novel bacteriocins. A colony MALDI-TOF MS procedure assisted in the identification of class I, II, and III lanthipeptides. MALDI-TOF MS and a targeted proteomics, combined with a massive peptide analysis (LC-MS/MS) approach, has proven valuable for the identification and biochemical characterization of previously described and novel bacteriocins encoded by the isolated bacteriocin-producing strains.

Invited review: Genomic modifications of lactic acid bacteria and their applications in dairy fermentation

Lactic acid bacteria (LAB) have a long history of safe use in milk fermentation and are generally recognized as health-promoting microorganisms when present in fermented foods. Lactic acid bacteria are also important components of the human intestinal microbiota and are widely used as probiotics. Considering their safe and health-beneficial properties, LAB are considered appropriate vehicles that can be genetically modified for food, industrial and pharmaceutical applications. Here, this review describes (1) the potential opportunities for application of genetically modified LAB strains in dairy fermentation and (2) the various genomic modification tools for LAB strains, such as random mutagenesis, adaptive laboratory evolution, conjugation, homologous recombination, recombineering, and CRISPR (clustered regularly interspaced short palindromic repeat)-Cas (CRISPR-associated protein)-based genome engineering. Finally, this review also discusses the potential future developments of these genomic modification technologies and their applications in dairy fermentations.

Quantification of nisin concentration from fluorescence-based antimicrobial activity assay using Bayesian calibration

Bacteriocins are ribosomally synthesized peptides with the innate ability to kill or inhibit growth of other bacteria. In recent years, bacteriocins have received increased interest, as their antimicrobial activity enhances food safety and shelf life by combatting pathogens such as Listeria monocytogenes. They also have application potential as an active pharmaceutical compound to combat multidrug-resistant pathogens. As new bacteriocins continue to be discovered, accelerated workflows for screening, identification, and process development have been developed. However, antimicrobial activity measurement is often still limited with regards to quantification and throughput. Here, we present the use of a non-linear calibration model to infer nisin concentrations in cultivation supernatants of Lactococcus lactis ssp. lactis B1629 using readouts of pHluorin2 fluorescence-based antimicrobial activity assays.

Potential probiotic Lactiplantibacillus plantarum DS1800 extends lifespan and enhances stress resistance in Caenorhabditis elegans model

Probiotics are live microorganisms that provide health benefits when administered in appropriate amounts by improving or restoring the balance of intestinal microbiota. Various functional probiotic products have been developed due to the growing interest in the health-promoting and anti-aging effects of enhancing the gut microbiome. Lactiplantibacillus plantarum species are known for their potential to extend lifespan. However, this activity is strain or isolation source specific, necessitating the identification of individual strain functionalities. This study used the C. elegans model to screen probiotics for life-extension effects and analyze their functions. The 43 lactic-acid bacteria strains isolated from fermented foods, breast milk, and human feces were subjected to longevity assays, and L. plantarum DS1800 was selected to demonstrate the most effective lifespan extension. The average lifespan of Caenorhabditis elegans fed DS1800 increased by 17.36% compared with those fed Escherichia coli OP50. Further analysis of the expression of key genes related to longevity revealed the high expression of the skinhead-1 (skn-1), antibacterial, and heat stress resistance genes via the p38 MAPK pathway. These expression patterns suggest that DS1800 extends the lifespan of C. elegans by enhancing its stress resistance and protecting it against pathogens. Additionally, DS1800 exhibited excellent intestinal adhesion, with 7.56% adhesion to HT-29 cells. Therefore, L. plantarum DS1800 is effective in extending the lifespan of C. elegans and can be used as a functional probiotic.

Impact of a teat disinfectant based on Lactococcus cremoris on the cow milk proteome

BACKGROUND

Dairy cow milking practices require cleaning and disinfection of the teat skin before and after milking to ensure the safety and quality of milk and prevent intramammary infections. Antimicrobial proteins of natural origin can be valuable alternatives to traditional disinfectants. In a recent field trial, we demonstrated that a teat dip based on a nisin A-producing Lactococcus cremoris (L) had comparable efficacy to conventional iodophor dip (C) in preventing dairy cow mastitis. Here, we present the differential shotgun proteomics investigation of the milk collected during the trial.

METHODS

Four groups of quarter milk samples with low (LSCC) and high somatic cell count (HSCC) collected at the beginning (T0) and end (TF) of the trial were analyzed for a total of 28 LSCC (14 LSCC T0 and 14 LSCC TF) and 12 HSCC (6 HSCC T0 and 6 HSCC TF) samples. Milk proteins were digested into peptides, separated by nanoHPLC, and analyzed by tandem mass spectrometry (LC-MS/MS) on an Orbitrap Fusion Tribrid mass spectrometer. The proteins were identified with MaxQuant and interaction networks of the differential proteins were investigated with STRING. The proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifier PXD045030.

RESULTS

In healthy milk (LSCC), we detected 90 and 80 differential proteins at T0 and TF, respectively. At TF, the Lactococcus group showed higher levels of antimicrobial proteins. In mastitis milk (HSCC), we detected 88 and 106 differential proteins at T0 and TF, respectively. In the Lactococcus group, 14 proteins with antimicrobial and immune defense functions were enriched at TF vs. 4 proteins at T0. Cathelicidins were among the most relevant enriched proteins. Western immunoblotting validation confirmed the differential abundance.

CONCLUSIONS

At T0, the proteomic differences observed in healthy milk of the two groups were most likely dependent on physiological variation. On the other hand, antimicrobial and immune defense functions were higher in the milk of cows with mammary gland inflammation of the Lactococcus-treated group. Among other factors, the immunostimulatory action of nisin A might be considered as a contributor.

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.

Understanding of probiotic origin antimicrobial peptides: a sustainable approach ensuring food safety

The practice of preserving and adding value to food dates back to over 10,000 BCE, when unintentional microbial-driven chemical reactions imparted flavor and extended the shelf life of fermented foods. The process evolved, and with the urbanization of society, significant shifts in dietary habits emerged, accompanied by sporadic food poisoning incidents. The repercussions of the COVID-19 pandemic have intensified the search for antibiotic alternatives owing to the rise in antibiotic-resistant pathogens, emphasizing the exploration of probiotic-origin antimicrobial peptides to alleviate human microbiome collateral damage. Often termed 'molecular knives', these peptides outstand as potent antimicrobials due to their compatibility with innate microflora, amenability to bioengineering, target specificity, versatility and rapidity in molecular level mode of action. This review centres on bacteriocins sourced from lactic acid bacteria found in ethnic fermented foods, accentuating their desirable attributes, technological applications as nanobiotics and potential future applications in the modern context of ensuring food safety.

Raffinocyclicin is a novel plasmid-encoded circular bacteriocin produced by Lactococcus raffinolactis with broad-spectrum activity against many gram-positive food pathogens

This study describes the discovery and characterization of raffinocyclicin, a novel plasmid-encoded circular bacteriocin, produced by the raw milk isolate Lactococcus raffinolactis APC 3967. This bacteriocin has a molecular mass of 6,092 Da and contains 61 amino acids with a three-amino acid leader peptide. It shows the highest identity to the circular bacteriocins bacicyclicin XIN-1 (42.62%), aureocyclicin 4185 (42.62%), and garvicin ML (41.53%). A broad inhibitory spectrum includes strains from Staphylococcus, Enterococcus, Streptococcus, Micrococcus, Lactobacillus, Leuconostoc, and Listeria, in addition to a pronounced inhibitory effect against Lactococcus and Clostridium. It displays low sensitivity to trypsin, most likely as a result of its circular nature. The raffinocyclicin gene cluster is composed of 10 genes: 6 core genes, genes encoding an accessory three-component ABC transporter (rafCDE), and a putative transcriptional regulator related to the MutR family. A lack of inhibitory activity in the cell-free supernatant combined with the pronounced activity of cell extracts suggests that the majority of raffinocyclicin is associated with the cell rather than being released to the extracellular environment. This is the first report of a bacteriocin produced by the L. raffinolactis species.IMPORTANCEThe present study aimed to characterize raffinocyclicin, a novel circular bacteriocin produced by the lactic acid bacteria Lactococcus raffinolactis APC 3967. Bacteriocins are generally cationic and hydrophobic peptides with antimicrobial activity, which present diverse biotechnological properties of interest for the food industry. Raffinocyclicin inhibits a wide range of bacteria, including foodborne pathogens, and is stable against different treatments which suggest its potential as a natural biopreservative. Whole-genome sequencing and the genetic analysis of the raffinocyclicin gene cluster showed that it is encoded by plasmid that could be used in the future to transfer the ability to produce the bacteriocin to other lactic acid bacteria for industrial applications. These results together highlight the potential of this novel antimicrobial as a biopreservative to be used by the food industry.

Bacteriocin diversity, function, discovery and application as antimicrobials

Bacteriocins are potent antimicrobial peptides that are produced by bacteria. Since their discovery almost a century ago, diverse peptides have been discovered and described, and some are currently used as commercial food preservatives. Many bacteriocins exhibit extensively post-translationally modified structures encoded on complex gene clusters, whereas others have simple linear structures. The molecular structures, mechanisms of action and resistance have been determined for a number of bacteriocins, but most remain incompletely characterized. These gene-encoded peptides are amenable to bioengineering strategies and heterologous expression, enabling metagenomic mining and modification of novel antimicrobials. The ongoing global antimicrobial resistance crisis demands that novel therapeutics be developed to combat infectious pathogens. New compounds that are target-specific and compatible with the resident microbiota would be valuable alternatives to current antimicrobials. As bacteriocins can be broad or narrow spectrum in nature, they are promising tools for this purpose. However, few bacteriocins have gone beyond preclinical trials and none is currently used therapeutically in humans. In this Review, we explore the broad diversity in bacteriocin structure and function, describe identification and optimization methods and discuss the reasons behind the lack of translation beyond the laboratory of these potentially valuable antimicrobials.

Clean-label alternatives for food preservation: An emerging trend

Consumer demand for natural or 'clean-label' food ingredients has risen over the past 50 years and continues growing. Consumers have become more aware of their health and, therefore, insist on transparency in the list of ingredients. Preservatives are the most crucial food additives, ensuring food safety and security. Despite tremendous technological advancements, food preservation remains a significant challenge worldwide, primarily because most are synthetic and non-biodegradable. As a result, the food industry is placing more value on microbiota and other natural sources for bio-preservation, leading to the substitution of conventional processing and chemical preservatives with natural alternatives to ensure 'clean-label.' General Standard for Food Additives (GSFA) includes some of these 'clean-label' options in its list of additives. However, they are very rarely capable of replacing a synthetic preservative on a 'one-for-one' basis, putting pressure on researchers to decipher newer, cleaner, and more economical alternatives. Academic and scientific research has led to the discovery of several plant, animal, and microbial metabolites that may function as effective bio-preservatives. However, most have not yet been put in the market or are under trial. Hence, the present review aims to summarise such relevant and potential metabolites with bio-preservative properties comprehensively. This article will help readers comprehend recent innovations in the 'clean-label' era, provide informed choices to consumers, and improve the business of regulatory approvals.

Exploring pathological link between antimicrobial and amyloid peptides

Amyloid peptides (AMYs) and antimicrobial peptides (AMPs) are considered as the two distinct families of peptides, characterized by their unique sequences, structures, biological functions, and specific pathological targets. However, accumulating evidence has revealed intriguing pathological connections between these peptide families in the context of microbial infection and neurodegenerative diseases. Some AMYs and AMPs share certain structural and functional characteristics, including the ability to self-assemble, the presence of β-sheet-rich structures, and membrane-disrupting mechanisms. These shared features enable AMYs to possess antimicrobial activity and AMPs to acquire amyloidogenic properties. Despite limited studies on AMYs-AMPs systems, the cross-seeding phenomenon between AMYs and AMPs has emerged as a crucial factor in the bidirectional communication between the pathogenesis of neurodegenerative diseases and host defense against microbial infections. In this review, we examine recent developments in the potential interplay between AMYs and AMPs, as well as their pathological implications for both infectious and neurodegenerative diseases. By discussing the current progress and challenges in this emerging field, this account aims to inspire further research and investments to enhance our understanding of the intricate molecular crosstalk between AMYs and AMPs. This knowledge holds great promise for the development of innovative therapies to combat both microbial infections and neurodegenerative disorders.

Screening canine sources for novel antimicrobials reveals the circular broad-spectrum bacteriocin, caledonicin, produced by Staphylococcus caledonicus

Introduction

Antimicrobial-resistant pathogens present an ongoing threat to human and animal health, with deaths linked to antimicrobial resistance (AMR) predicted to increase annually. While the misuse and overuse of antibiotics in humans undoubtedly contribute to this escalation, antibiotic use in the veterinary field, including companion animals, also plays a contributing role. Pet owners' desire to improve the quality of life of their pets is likely to support antibiotic use in this field. Consequently, there is a need for antibiotic alternatives to treat bacterial infections. This study set out to screen for antimicrobial peptides known as bacteriocins from bacterial isolates of aerobic/microaerophilic environments of canine sources and determine their potential as antibiotic alternatives against clinically relevant pathogens.

Methods

Following a laboratory-based protocol, 22 bacterial isolates were subjected to whole-genome sequencing (WGS), and a total of 14 putative novel bacteriocins were identified from both class I and II bacteriocin classes. One particular bacteriocin, herein named caledonicin, was identified via in silico analysis from a Staphylococcus caledonicus strain and partially purified for further in vitro evaluation.

Results

Caledonicin is a 64-amino acid (IAANLGVSSGTAYS MANALNNISNVATA LTIIGTFTGVGTIGSGIA ATILAILKKKGVAAAAAF) novel circular bacteriocin most closely related to enterocin_NKR-5-3B based on core peptide alignment (39.1%), with a molecular weight of 6077.1 Da. Caledonicin exhibits a broad-spectrum of activity against a range of pathogenic bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus pseudintermedius (MRSP), and Listeria monocytogenes; and the gut-related bacterium associated with Crohn's disease, Mediterraneibacter gnavus ATCC 29149 (previously Ruminococcus gnavus ATCC 29149).

Discussion

This represents the first bacteriocin screening study involving bacteria from canine sources and confirms this is a rich environment for bacteriocin-producing strains. This study also identifies and characterises the first novel bacteriocin from the staphylococcal species, Staphylococcus caledonicus.

Dual bacteriocin and extracellular vesicle-mediated inhibition of Campylobacter jejuni by the potential probiotic candidate Ligilactobacillus salivarius UO.C249

Campylobacter jejuni (C. jejuni) is one of the most common causes of foodborne infections worldwide and a major contributor to diarrheal diseases. This study aimed to explore the ability of commensal gut bacteria to control C. jejuni infection. Bacterial strains from the intestinal mucosa of broilers were screened in vitro against C. jejuni ATCC BAA1153. The cell-free supernatant (CFS) of Ligilactobacillus salivarius UO.C249 showed potent dose-dependent antimicrobial activity against the pathogen, likely due to the presence of bacteriocin-like moieties, as confirmed by protease treatment. Genome and exoproteome analyses revealed the presence of known bacteriocins, including Abp118. The genome of Lg. salivarius UO.C249 harbors a 1.8-Mb chromosome and a 203-kb megaplasmid. The strain was susceptible to several antibiotics and had a high survival rate in the simulated chicken gastrointestinal tract (GIT). Post-protease treatment revealed residual inhibitory activity, suggesting alternative antimicrobial mechanisms. Short-chain fatty acid (SCFA) quantification confirmed non-inhibitory levels of acetic (24.4 ± 1.2 mM), isovaleric (34 ± 1.0 µM), and butyric (32 ± 2.5 µM) acids. Interestingly, extracellular vesicles (EVs) isolated from the CFS of Lg. salivarius UO.C249 were found to inhibit C. jejuni ATCC BAA-1153. Proteome profiling of these EVs revealed the presence of unique proteins distinct from bacteriocins identified in CFS. The majority of the identified proteins in EVs are located in the membrane and play roles in transmembrane transport and peptidoglycan degradation, peptidase, proteolysis, and hydrolysis. These findings suggest that although bacteriocins are a primary antimicrobial mechanism, EV production also contributes to the inhibitory activity of Lg. salivarius UO.C249 against C. jejuni.

IMPORTANCE

Campylobacter jejuni (C. jejuni) is a major cause of gastroenteritis and a global public health concern. The increasing antibiotic resistance and lack of effective alternatives in livestock production pose serious challenges for controlling C. jejuni infections. Therefore, alternative strategies are needed to control this pathogen, especially in the poultry industry where it is prevalent and can be transmitted to humans through contaminated food products. In this study, Ligilactobacillus salivarius UO.C249 isolated from broiler intestinal mucosa inhibited C. jejuni and exhibited important probiotic features. Beyond bacteriocins, Lg. salivarius UO.C249 secretes antimicrobial extracellular vesicles (EVs) with a unique protein set distinct from bacteriocins that are involved in transmembrane transport and peptidoglycan degradation. Our findings suggest that beyond bacteriocins, EV production is also a distinct inhibitory signaling mechanism used by Lg. salivarius UO.C249 to control C. jejuni. These findings hold promise for the application of probiotic EVs for pathogen control.

Bacteriocins sourced from traditional fermented foods for ensuring food safety: the microbial guards

Concerns about food safety have consistently driven the exploration of potent antimicrobials with probiotic origins. Identification of probiotic-derived bacteriocins as robust alternatives to antibiotics has gained traction following the COVID-19 pandemic. Additionally, the global market is witnessing an increasing preference for minimally processed food products free from chemical additives. Another contributing factor to the search for potent antimicrobials is the escalating number of infections caused by antibiotic-resistant bacteria and the need to mitigate the significant damage inflicted on the commensal human microbiota by broad-spectrum antibiotics. As an alternative bio-preservation strategy, there is substantial enthusiasm for the use of bacteriocins or starter cultures producing bacteriocins in preserving a variety of food items. This review specifically focuses on bacteriocins originating from lactic acid bacteria associated with fermented foods and explores their technological applications as nanobiotics. The food-grade antibiotic alternatives, whether utilized independently or in combination with other antimicrobials and administered directly or encapsulated, are anticipated to possess qualities of safety, stability and non-toxicity suitable for application in the food sector. © 2024 Society of Chemical Industry.

Enterocin LD3 from Enterococcus hirae LD3 Inhibits the Growth of Salmonella enterica subsp. enterica serovar Typhimurium ATCC 13311 in Fruit Juice

In order to prevent the growth of pathogens in food, bacteriocins produced by various probiotic lactic acid bacteria have been recognized as potential substitutes of chemical preservatives. In this study, enterocin LD3 was purified from the cell-free supernatant of a food isolate, Enterococcus hirae LD3 using multistep chromatography. In the fruit juice, lethal concentration (LC50) of enterocin LD3 was found to be 260 µg/mL against Salmonella enterica subsp. enterica serovar Typhimurium ATCC 13311. The cells treated with enterocin LD3 were red colour indicating dead cells after propidium iodide staining, while untreated cells were found blue after staining with 4', 6-diamidino-2-phenylindole. The mechanism of cell killing was analyzed using infrared spectrum of cells treated with enterocin LD3 which was found altered in the range of 1,094.30 and 1,451.82 cm-1 corresponding to nucleic acids and phospholipids, respectively. The morphology of target cells were severely ruptured and lysed as observed under electron microscopy. Thus, the present study suggested that enterocin LD3 showed bactericidal activity against Salm. enterica subsp. enterica serovar Typhimurium ATCC 13311 and may be applied as a bio-preservative for the safety of fruit juices.

Therapeutic Strategies to Combat Increasing Rates of Multidrug Resistant Pathogens

The emergence of antimicrobic-resistant infectious pathogens and the consequent rising in the incidence and prevalence of demises caused by or associated to infections which are not sensitive to drug treatments is one of today's major global health challenges. Antimicrobial resistance (AMR) can bring to therapeutic failure, infection's persistence and risk of serious illness, in particular in vulnerable populations such as the elderly, patients with neoplastic diseases or the immunocompromised. It is assessed that AMR will induce until 10 million deaths per year by 2050, becoming the leading cause of disease-related deaths. The World Health Organisation (WHO) and the United Nations General Assembly urgently call for new measures to combat the phenomenon. Research and development of new antimicrobial agents has decreased due to market failure. However, promising results are coming from new alternative therapeutic strategies such as monoclonal antibodies, microbiome modulators, nanomaterial-based therapeutics, vaccines, and phages. This narrative review aimed to analyse the benefits and weaknesses of alternative therapeutic strategies to antibiotics which treat multidrug-resistant bacterial infections.

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

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

A review of immune modulators and immunotherapy in infectious diseases

The human immune system responds to harmful foreign invaders frequently encountered by the body and employs defense mechanisms to counteract such assaults. Various exogenous and endogenous factors play a prominent role in maintaining the balanced functioning of the immune system, which can result in immune suppression or immune stimulation. With the advent of different immune-modulatory agents, immune responses can be modulated or regulated to control infections and other health effects. Literature provides evidence on various immunomodulators from different sources and their role in modulating immune responses. Due to the limited efficacy of current drugs and the rise in drug resistance, there is a growing need for new therapies for infectious diseases. In this review, we aim to provide a comprehensive overview of different immune-modulating agents and immune therapies specifically focused on viral infectious diseases.

Addition of nisin to high-viscosity glass-ionomer cement: a comparative in vitro study on antibacterial and physical properties

PURPOSE

Nisin is a lantibiotic effective against Gram-positive microorganisms such as Streptococcus mutans. The study aimed to determine the effect of the addition of nisin to high-viscosity glass-ionomer cement (HVGIC) on its antibacterial activity, setting time, surface microhardness, and compressive strength.

METHODS

1 and 3% w/w nisin were added to HVGIC before mixing. Unmodified HVGIC was the control. Agar disc diffusion, direct contact test, and scanning electron microscopy (SEM) analysis were used to evaluate antibacterial activity against S. mutans. Setting time, surface microhardness, and compressive strength were measured using Gilmore needle apparatus, digital microhardness tester, and universal testing machine, respectively. Statistical analysis included Student's t test, one-way ANOVA with Tamhane's post hoc test, and repeated-measures ANOVA.

RESULTS

As evidenced by the agar disc diffusion (p < 0.001), direct contact tests (p = 0.025), and SEM analysis of the S. mutans cell count and cell surface area (p = 0.049 and 0.003), 3% nisin had the strongest antibacterial activity. There was a dose-dependent increase in setting time (p = 0.005) and surface microhardness (p = 0.006), with no significant difference in compressive strength compared to control.

CONCLUSION

The addition of 3% nisin to HVGIC enhances the antibacterial action against S. mutans and surface microhardness without adversely affecting setting time and compressive strength.

High-throughput detection of potential bacteriocin producers in a large strain library using live fluorescent biosensors

The global increase in antibiotic resistances demands for additional efforts to identify novel antimicrobials such as bacteriocins. These antimicrobial peptides of bacterial origin are already used widely in food preservation and promising alternatives for antibiotics in animal feed and some clinical setting. Identification of novel antimicrobials is facilitated by appropriate high throughput screening (HTS) methods. Previously, we have described a rapid, simple and cost-efficient assay based on live biosensor bacteria for detection of antimicrobial compounds that act on membrane integrity using the ratiometric pH-dependent fluorescent protein pHluorin2 (pHin2). Here, we use these biosensors to develop an integrated pipeline for high-throughput identification of bacteriocin producers and their biosynthetic gene clusters. We extend the existing portfolio of biosensors by generating pHin2 expressing strains of Escherichia coli, Bacillus cereus, Staphylococcus epidermidis, and methicillin-resistant Staphylococcus aureus. These strains were characterized, and control experiments were performed to assess heterogeneity of these biosensors in response to known bacteriocins and develop a robust HTS system. To allow detection of compounds that inhibit target bacteria by inhibiting growth without disturbing membrane integrity, the HTS system was extended with a growth-dependent readout. Using this HTS system, we screened supernatants of a total of 395 strains of a collection of lactic acid bacteria. After two rounds of screening 19 strains of the collection were identified that produced antimicrobial activity against Listeria innocua and Listeria monocytogenes. Genomes of confirmed hits were sequenced and annotated. In silico analysis revealed that the identified strains encode between one and six biosynthetic gene clusters (BGCs) for bacteriocins. Our results suggest that pHin2 biosensors provides a flexible, cheap, fast, robust and easy to handle HTS system for identification of potential bacteriocins and their BGCs in large strain collections.

Clostridioides difficile and Gut Microbiota: From Colonization to Infection and Treatment

Clostridioides difficile is the main causative agent of antibiotic-associated diarrhea (AAD) in hospitals in the developed world. Both infected patients and asymptomatic colonized individuals represent important transmission sources of C. difficile. C. difficile infection (CDI) shows a large range of symptoms, from mild diarrhea to severe manifestations such as pseudomembranous colitis. Epidemiological changes in CDIs have been observed in the last two decades, with the emergence of highly virulent types and more numerous and severe CDI cases in the community. C. difficile interacts with the gut microbiota throughout its entire life cycle, and the C. difficile's role as colonizer or invader largely depends on alterations in the gut microbiota, which C. difficile itself can promote and maintain. The restoration of the gut microbiota to a healthy state is considered potentially effective for the prevention and treatment of CDI. Besides a fecal microbiota transplantation (FMT), many other approaches to re-establishing intestinal eubiosis are currently under investigation. This review aims to explore current data on C. difficile and gut microbiota changes in colonized individuals and infected patients with a consideration of the recent emergence of highly virulent C. difficile types, with an overview of the microbial interventions used to restore the human gut microbiota.

Development of transcriptional factor-based whole-cell biosensors to monitor and degrade antibiotics using mutant cells obtained via adaptive laboratory evolution

With the widespread use of antibiotics and increasing environmental concerns regarding antibiotic abuse, the detection and degradation of antibiotic residues in various samples has become a pressing issue. Transcriptional factor (TF)-based whole-cell biosensors are low-cost, easy-to-use, and flexible tools for detecting chemicals and controlling bioprocesses. However, because of cytotoxicity caused by antibiotics, the application of such biosensors is limited in the presence of antibiotics. In this study, we used antibiotic-tolerant mutants obtained via adaptive laboratory evolution (ALE) to develop TF-based whole-cell biosensors for antibiotic monitoring and degradation. The biosensors had high performance and stability in detecting relatively high concentrations of tetracycline (Tc) and nisin. The ALE mutant-based Tc biosensor exhibited a 10-fold larger linear detection range than the wild-type strain-based biosensor. Then, the Tc biosensor was employed to detect residual amounts of Tc in mouse stool, serum, and urine samples and facilitate Tc biodegradation in mouse stool, demonstrating its high utility. Considering that ALE has been demonstrated to enhance cell tolerance to various toxic chemicals, our strategy might facilitate the development of whole-cell biosensors for most antibiotics and other toxic ligands.

Unveiling the mechanism of essential oil action against skin pathogens: from ancient wisdom to modern science

Essential oils are among the most well-known phyto-compounds, and since ancient times, they have been utilized in medicine. Over 100 essential oils have been identified and utilized as therapies for various skin infections and related ailments. While numerous commercial medicines are available in different dosage forms to treat skin diseases, the persisting issues include their side effects, toxicity, and low efficacy. As a result, researchers are seeking novel classes of compounds as substitutes for synthetic drugs, aiming for minimal side effects, no toxicity, and high efficacy. Essential oils have shown promising antimicrobial activity against skin-associated pathogens. This review presents essential knowledge and scientific information regarding essential oil's antimicrobial capabilities against microorganisms that cause skin infections. Essential oils mechanisms against different pathogens have also been explored. Many essential oils exhibit promising activity against various microbes, which has been qualitatively assessed using the agar disc diffusion experiment, followed by determining the minimum inhibitory concentration for quantitative evaluation. It has been observed that Staphylococcus aureus and Candida albicans have been extensively researched in the context of skin-related infections and their antimicrobial activity, including established modes of action. In contrast, other skin pathogens such as Staphylococcus epidermidis, Streptococcus pyogens, Propionibacterium acnes, and Malassezia furfur have received less attention or neglected. This review report provides an updated understanding of the mechanisms of action of various essential oils with antimicrobial properties. This review explores the anti-infectious activity and mode of action of essential against distinct skin pathogens. Such knowledge can be valuable in treating skin infections and related ailments.

Bacteriocins in Cancer Treatment: Mechanisms and Clinical Potentials

Cancer poses a severe threat to human health. Although conventional chemotherapy remains a cornerstone of cancer treatment, its significant side effects and the growing issue of drug resistance necessitate the urgent search for more efficient and less toxic anticancer drugs. In recent years, bacteriocins, antimicrobial peptides of microbial origin, have garnered significant attention due to their targeted antitumor activity. This unique activity is mainly attributed to their cationic and amphiphilic nature, which enables bacteriocins to specifically kill tumor cells without harming normal cells. When involving non-membrane-disrupting mechanisms, such as apoptosis induction, cell cycle blockade, and metastasis inhibition, the core mechanism of action is achieved by disrupting cell membranes, which endows bacteriocins with low drug resistance and high selectivity. However, the susceptibility of bacteriocins to hydrolysis and hemolysis in vivo limits their clinical application. To overcome these challenges, structural optimization of bacteriocins or their combination with nanotechnology is proposed for future development. This review aims to study the mechanism of action and current research status of bacteriocins as anticancer treatments, thus providing new insights for their clinical development and application.

Bacteriocinogenic anti-listerial properties and safety assessment of Enterococcus faecium and Lactococcus garvieae strains isolated from Brazilian artisanal cheesemaking environment

AIMS

This study aimed to prospect and isolate lactic acid bacteria (LAB) from an artisanal cheese production environment, to assess their safety, and to explore their bacteriocinogenic potential against Listeria monocytogenes.

METHODS AND RESULTS

Samples were collected from surfaces of an artisanal-cheese production facility and after rep-PCR and 16S rRNA sequencing analysis, selected strains were identified as to be belonging to Lactococcus garvieae (1 strain) and Enterococcus faecium (14 isolates, grouped into three clusters) associated with different environments (worktables, cheese mold, ripening wooden shelves). All of them presented bacteriocinogenic potential against L. monocytogenes ATCC 7644 and were confirmed as safe (γ-hemolytic, not presenting antibiotic resistance, no mucus degradation properties, and no proteolytic or gelatinase enzyme activity). Additionally, cell growth, acidification and bacteriocins production kinetics, bacteriocin stability in relation to different temperatures, pH, and chemicals were evaluated. According to performed PCR analysis all studied strains generated positive evidence for the presence of entA and entP genes (for production of enterocins A and enterocins P, respectively). However, pediocin PA-1 associated gene was recorded only in DNA obtained from E. faecium ST02JL and Lc. garvieae ST04JL.

CONCLUSIONS

It is worth considering the application of these safe LAB or their bacteriocins in situ as an alternative means of controlling L. monocytogenes in cheese production environments, either alone or in combination with other antimicrobials.

Nisin variants: What makes them different and unique?

Nisin A is a lantibiotic bacteriocin typically produced by strains of Lactococcus lactis. This bacteriocin has been approved as a natural food preservative since the late 1980 s and shows antimicrobial activity against a range of food-borne spoilage and pathogenic microorganisms. The therapeutic potential of nisin A has also been explored increasingly both in human and veterinary medicine. Nisin has been shown to be effective in treating bovine mastitis, dental caries, cancer, and skin infections. Recently, it was demonstrated that nisin has an affinity for the same receptor used by SARS-CoV-2 to enter human cells and was proposed as a blocker of the viral infection. Several nisin variants produced by distinct bacterial strains or modified by bioengineering have been described since the discovery of nisin A. These variants present modifications in the peptide structure, biosynthesis, mode of action, and spectrum of activity. Given the importance of nisin for industrial and therapeutic applications, the objective of this study was to describe the characteristics of the nisin variants, highlighting the main differences between these molecules and their potential applications. This review will be useful to researchers interested in studying the specifics of nisin A and its variants.

Microcin C7 as a Potential Antibacterial-Immunomodulatory Agent in the Postantibiotic Era: Overview of Its Bioactivity Aspects and Applications

In the postantibiotic era, the pathogenicity and resistance of pathogens have increased, leading to an increase in intestinal inflammatory disease. Bacterial infections remain the leading cause of animal mortality. With increasing resistance to antibiotics, there has been a significant decrease in resistance to both inflammation and disease in animals, thus decreasing production efficiency and increasing production costs. These side effects have serious consequences and have detracted from the development of China's pig industry. Microcin C7 (McC7) demonstrates potent antibacterial activity against a broad spectrum of pathogens, stable physicochemical properties, and low toxicity, reducing the likelihood of resistance development. Thus, McC7 has received increasing attention as a potential clinical antibacterial and immunomodulatory agent. McC7 has the potential to serve as a new generation of antibiotic substitutes; however, its commercial applications in the livestock and poultry industry have been limited. In this review, we summarize and discuss the biosynthesis, biochemical properties, structural characteristics, mechanism of action, and immune strategies of McC7. We also describe the ability of McC7 to improve intestinal health. Our aim in this study was to provide a theoretical basis for the application of McC7 as a new feed additive or new veterinary drug in the livestock and poultry breeding industry, thus providing a new strategy for alleviating resistance through feed and mitigating drug resistance. Furthermore, this review provides insight into the new functions and anti-infection mechanisms of bacteriocin peptides and proposes crucial ideas for the research, product development, and application of bacteriocin peptides in different fields, such as the food and medical industries.

Antimicrobial Resistance in Livestock: A Serious Threat to Public Health

Antimicrobial resistance represents an alarming public health problem; its importance is related to the significant clinical implications (increased morbidity, mortality, disease duration, development of comorbidities, and epidemics), as well as its economic effects on the healthcare sector. In fact, therapeutic options are severely limited by the advent and spread of germs resistant to many antibiotics. The situation worldwide is worrying, especially in light of the prevalence of Gram-negative bacteria-Klebsiella pneumoniae and Acinetobacter baumannii-which are frequently isolated in hospital environments and, more specifically, in intensive care units. The problem is compounded by the ineffective treatment of infections by patients who often self-prescribe therapy. Resistant bacteria also show resistance to the latest generation antibiotics, such as carbapenems. In fact, superbacteria, grouped under the acronym extended-spectrum betalactamase (ESBL), are becoming common. Antibiotic resistance is also found in the livestock sector, with serious repercussions on animal production. In general, this phenomenon affects all members of the biosphere and can only be addressed by adopting a holistic "One Health" approach. In this literature overview, a stock is taken of what has been learned about antibiotic resistance, and suggestions are proposed to stem its advance.

Biosynthesis, classification, properties, and applications of Weissella bacteriocins

This review aims to comprehensively chronicle the biosynthesis, classification, properties, and applications of bacteriocins produced by Weissella genus strains, particularly emphasizing their potential benefits in food preservation, human health, and animal productivity. Lactic Acid Bacteria (LAB) are a class of microorganisms well-known for their beneficial role in food fermentation, probiotics, and human health. A notable property of LAB is that they can synthesize antimicrobial peptides known as bacteriocins that exhibit antimicrobial action against both closely related and other bacteria as well. Bacteriocins produced by Weissella spp. are known to exhibit antimicrobial activity against several pathogenic bacteria including food spoilage species, making them highly invaluable for potential application in food preservation and food safety. Importantly, they provide significant health benefits to humans, including combating infections, reducing inflammation, and modulating the gut microbiota. In addition to their applications in food fermentation and probiotics, Weissella bacteriocins show promising prospects in poultry production, processing, and improving animal productivity. Future research should explore the utilization of Weissella bacteriocins in innovative food safety measures and medical applications, emphasizing their potential to combat antibiotic-resistant pathogens, enhance gut microbiota composition and function, and synergize with existing antimicrobial therapies.