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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.In this Review, Sugrue, Ross and Hill explore recent developments in bacteriocin research, including new discoveries and bioengineering approaches for improved activity, and discuss their application in microbiome modulation and clinical potential.

Lactic acid bacteria (LAB) constitute a heterogeneous group of microorganisms that produce lactic acid as the major product during the fermentation process. LAB are Gram-positive bacteria with great biotechnological potential in the food industry. They can produce bacteriocins, which are proteinaceous antimicrobial molecules with a diverse genetic origin, posttranslationally modified or not, that can help the producer organism to outcompete other bacterial species. In this review, we focus on the various types of bacteriocins that can be found in LAB and the organization and regulation of the gene clusters responsible for their production and biosynthesis, and consider the food applications of the prototype bacteriocins from LAB. Furthermore, we propose a revised classification of bacteriocins that can accommodate the increasing number of classes reported over the last years.

The microbiomes on human body surfaces affect health in multiple ways. They include not only commensal or mutualistic bacteria but also potentially pathogenic bacteria, which can enter sterile tissues to cause invasive infection. Many commensal bacteria produce small antibacterial molecules termed bacteriocins that have the capacity to eliminate specific colonizing pathogens; as such, bacteriocins have attracted increased attention as potential microbiome-editing tools. Metagenome-based and activity-based screening approaches have strongly expanded our knowledge of the abundance and diversity of bacteriocin biosynthetic gene clusters and the properties of a continuously growing list of bacteriocin classes. The dynamic acquisition, diversification or loss of bacteriocin genes can shape the fitness of a bacterial strain that is in competition with bacteriocin-susceptible bacteria. However, a bacteriocin can only provide a competitive advantage if its fitness benefit exceeds the metabolic cost of production, if it spares crucial mutualistic partner strains and if major competitors cannot develop resistance. In contrast to most currently available antibiotics, many bacteriocins have only narrow activity ranges and could be attractive agents for precision therapy and prevention of infections. A common scientific strategy involving multiple disciplines is needed to uncover the immense potential of microbiome-shaping bacteriocins.Small antibacterial molecules termed bacteriocins can influence microbiome composition by providing an advantage to bacteriocin producers over bacteriocin-sensitive strains. In this Review, Peschel and colleagues provide an overview of the types of bacteriocins, their costs and benefits, and how they may provide new avenues for antibacterial drug development.

Mediterraneibacter gnavus is a core member of the gut microbiome and implicated in several diseases. Direct competition between M. gnavus and other members of the microbiome may contribute to the shift from a diverse, structured community to dysbiosis observed in disease. Identifying molecular mechanisms of microbial competition will aid future studies of these disease-relevant bacteria and clarify how community structure is maintained. We report the discovery of mediterrocin, a bacteriocin present in many species in the orders Lachnospirales and Eubacteriales, but clade-specific within M. gnavus . Mediterrocin, produced by health-associated strains of M. gnavus , inhibits the growth of disease-associated M. gnavus strains and a broad spectrum of gut commensal bacteria and pathogens.

Intestinal commensal bacteria can inhibit dense colonization of the gut by vancomycin-resistant Enterococcus faecium (VRE), a leading cause of hospital-acquired infections 1 , 2 . A four-strained consortium of commensal bacteria that contains Blautia producta BP SCSK can reverse antibiotic-induced susceptibility to VRE infection 3 . Here we show that BP SCSK reduces growth of VRE by secreting a lantibiotic that is similar to the nisin-A produced by Lactococcus lactis . Although the growth of VRE is inhibited by BP SCSK and L. lactis in vitro, only BP SCSK colonizes the colon and reduces VRE density in vivo. In comparison to nisin-A, the BP SCSK lantibiotic has reduced activity against intestinal commensal bacteria. In patients at high risk of VRE infection, high abundance of the lantibiotic gene is associated with reduced density of E. faecium . In germ-free mice transplanted with patient-derived faeces, resistance to VRE colonization correlates with abundance of the lantibiotic gene. Lantibiotic-producing commensal strains of the gastrointestinal tract reduce colonization by VRE and represent potential probiotic agents to re-establish resistance to VRE. The gut commensal Blautia producta secretes a lantibiotic that reduces colonization of the gut by the major pathogen vancomycin-resistant Enterococcus faecium , and transplantation of microbiota with high abundance of the lantibiotic gene enhances resistance to colonization in mice.

Members of the genus Bacillus are known to produce a wide arsenal of antimicrobial substances, including peptide and lipopeptide antibiotics, and bacteriocins. Many of the Bacillus bacteriocins belong to the lantibiotics, a category of post-translationally modified peptides widely disseminated among different bacterial clades. Lantibiotics are among the best-characterized antimicrobial peptides at the levels of peptide structure, genetic determinants and biosynthesis mechanisms. Members of the genus Bacillus also produce many other nonmodified bacteriocins, some of which resemble the pediocin-like bacteriocins of the lactic acid bacteria (LAB), while others show completely novel peptide sequences. Bacillus bacteriocins are increasingly becoming more important due to their sometimes broader spectra of inhibition (as compared with most LAB bacteriocins), which may include Gram-negative bacteria, yeasts or fungi, in addition to Gram-positive species, some of which are known to be pathogenic to humans and/or animals. The present review provides a general overview of Bacillus bacteriocins, including primary structure, biochemical and genetic characterization, classification and potential applications in food preservation as natural preservatives and in human and animal health as alternatives to conventional antibiotics. Furthermore, it addresses their environmental applications, such as bioprotection against the pre- and post-harvest decay of vegetables, or as plant growth promoters.

Bacteriocins are heat-stable ribosomally synthesized antimicrobial peptides produced by various bacteria, including food-grade lactic acid bacteria (LAB). These antimicrobial peptides have huge potential as both food preservatives, and as next-generation antibiotics targeting the multiple-drug resistant pathogens. The increasing number of reports of new bacteriocins with unique properties indicates that there is still a lot to learn about this family of peptide antibiotics. In this review, we highlight our system of fast tracking the discovery of novel bacteriocins, belonging to different classes, and isolated from various sources. This system employs molecular mass analysis of supernatant from the candidate strain, coupled with a statistical analysis of their antimicrobial spectra that can even discriminate novel variants of known bacteriocins. This review also discusses current updates regarding the structural characterization, mode of antimicrobial action, and biosynthetic mechanisms of various novel bacteriocins. Future perspectives and potential applications of these novel bacteriocins are also discussed.

E50-52, a class IIa-peptidic bacteriocin produced by a strain of Enterococcus faecium, has broad-spectrum antimicrobial activity against various foodborne pathogens. However, effective utilization of the E50-52 has been limited by low production yields and challenges associated with separation and purification of this 39-amino acid antimicrobial peptide. In this study, we have successfully produced a biologically active recombinant form of E50-52 by fusing it with the 16-kDa catalytic domain of lysostaphin-class III bacteriocin (LssCAT), which resulted in high-yield production. Initially, the LssCAT-E50-52 chimeric protein was insoluble upon over-expression in Escherichia coli, but it became soluble using phosphate buffer (pH 7.4) supplemented with 8 M urea. Purification using immobilized-Ni2+ affinity chromatography under urea denaturing conditions resulted in consistent production a homogenous products (LssCAT-E50-52) with >95% purity. The purified protein was refolded using an optimized stepwise dialysis process. The resulting refolded LssCAT-E50-52 protein exhibited dose-dependent inhibitory activity against Helicobacter pylori, a Gram-negative, flagellated, helical bacterium that is associated with gastric cancer. Overall, the optimized protocol described in this study effectively produced large quantities of high-purity recombinant LssCAT-E50-52 protein, yielding approximately 100 mg per liter of culture. To the best of our knowledge, this is the first report on the impact of LssCAT-E50-52 on H. pylori. This finding could pave the way for further research into bactericidal mechanism and potential applications of this bacteriocin in biomedical industry.

Lactic acid bacteria (LAB) are Gram-positive and catalase-negative microorganisms used to produce fermented foods. They appear morphologically as cocci or rods and they do not form spores. LAB used in food fermentation are from the Lactobacillus and Bifidobacterium genera and are useful in controlling spoilage and pathogenic microbes, due to the bacteriocins and acids that they produce. Consequently, LAB and their bacteriocins have emerged as viable alternatives to chemical food preservatives, curtesy of their qualified presumption of safety (QPS) status. There is growing interest regarding updated literature on the applications of LAB and their products in food safety, inhibition of the proliferation of food spoilage microbes and foodborne pathogens, and the mitigation of viral infections associated with food, as well as in the development of creative food packaging materials. Therefore, this review explores empirical studies, documenting applications and the extent to which LAB isolates and their bacteriocins have been used in the food industry against food spoilage microorganisms and foodborne pathogens including viruses; as well as to highlight the prospects of their numerous novel applications as components of hurdle technology to provide safe and quality food products.

Background The emergence of serious issues of multidrug resistance in the past few years have enforced the use of bacteriocins for combating infections. Threat posed to public health by various multidrug resistant (MDR) organisms can be resolved by discovering new antimicrobial proteins with broad spectrum of inhibition. Results In the current study, Bacteriocin (BAC-IB17) produced by Bacillus subtilis KIBGE-IB17 is found to be effective against different strains of methicillin resistant Staphylococcus aureus (MRSA). The approximate molecular mass of BAC-IB17 is 10.7 kDa. This unique bacteriocin is found to be highly thermostable and pH stable in nature. It also showed its stability against various heavy metals, organic solvents, surfactants and proteolytic enzymes. Amino acid profile of BAC-IB17 clearly showed that this protein mainly consists of non-polar and basic amino acids whereas; some acidic amino acids were also detected. Sequence of first 15 amino acid residues obtained from N-terminal sequencing of BAC-IB17 were NKPEALVDYTGVXNS. Conclusions The anti-MRSA property of purified bacteriocin may be used to prevent the spread of MRSA infections. Remarkable features of BAC-IB17 suggests its applications in various pharmaceutical and food industries as it can function under a variety of harsh environmental conditions.