Bacteriocin

Bacteriocins are ribosomally-synthesized antibacterial peptides. These compounds are produced by a broad variety of different bacteria belonging mainly to the genus Bifidobacterium, to which health promoting properties have frequently been attributed. However, despite the fact that the identification of Bifidobacterium-associated bacteriocins was first reported in 1980 and that they exhibit antimicrobial activity against pathogenic microorganisms such as Listeria monocytogenes, Clostridium perfringens, and Escherichia coli, relatively little information is still available about the antimicrobial compounds produced by strains of this genus. More detailed understanding of the action mechanisms of these antimicrobials could allow us to determine the extent to which their production contributes to the probiotic properties of specific bifidobacteria strains and, potentially, be of crucial significance for ultimate preservation of functional foods or pharmaceutical applications. Here we review what is already known about their structure, classification, mode of action, functionality, immunity, production and purification.

Bacteriocins are ribosomally synthesised small antimicrobial peptides produced from a wide range of bacteria, and also rich sources for potential alternatives to traditional antibiotics. Many bacteriocins have highly specific antibacterial activity against target pathogens, even including drug-resistant bacteria such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus. As the final and essential step during biosynthesis, the leader sequence removal and exportation of matured bacteriocin are lacking of research and therefore the last to be understood. In respect of production, bacteriocin precursor peptides are processed and exported by a group of membrane proteins from the ATP-binding cassette transporter family. The main aims of this article are to summarise knowledge till now on the leader signal and correlated transporters for bacteriocin secretion in gram-positive bacteria in a review for the first time, to introduce different strategies for higher production, and to offer new insights into many essential but still unanswered questions above for the purpose of more efficient bacteriocin utilisation.

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.