Antimicrobial peptides produced by bacteria: The bacteriocins

Bacteriocins are the subset of antimicrobial peptides (AMPs) produced by bacteria. They are small amphipathic peptides that interact with bacterial membranes leading to cell death. Most of the best known are produced by lactic acid bacteria used as food fermentation starters, because of their potential use as food preservatives. Bacteriocins are divided into two groups: lantibiotics that present posttranslational condensation rings and unmodified peptides. The first are subdivided into elongated versus globular lantibiotics, while four subgroups are recognized among unmodified bacteriocins. The genetic organization is in clusters that may reside into plasmids or transposons, formed by the structural gene, the export and immunity determinants, the quorum sensing governing production and any modification genes. Bacteriocins are active at extremely low concentrations (nM range) due to a dual mode of action: (a) binding to the membrane phospholipids and (b) specific recognition of surface components, both of which collaborate in pore formation. Development of resistance to bacteriocins is very infrequent due to the presence of two targets and is usually due to unspecific modifications of the cell envelope. Bacteriocins are used as food preservatives, either after total or partial purification or as extracts of producing bacteria. In situ production is also used, with the advantage of producing early lysis of the starter bacteria and ripening acceleration of the fermented product. They may also form part of hurdle technologies and be incorporated into packaging systems to allow extended liberation. Medical and veterinary applications are in their infancy but good results have been obtained against infection by Gram-positive bacteria and Helicobacter pylori.Peer reviewe