Bacteriocins: developing innate immunity for food

Abstract

The use of antimicrobial peptides is arguably the most widespread system of antimicrobial defence, being present in various organisms from insects to plants to humans. However, multicellular organisms do not have a monopoly on this early-warning system — bacteriocins, antimicrobial peptides thought to be produced by 30–99% of Bacteria and Archaea — perform the same function, allowing their microbial producers to target other microorganisms while remaining immune themselves. The bacteriocins are a heterogeneous group of peptides and proteins and previously a classification scheme involving five separate classes was proposed. In this article, we suggest an alternative classification, which divides the bacteriocins into two distinct categories: the lanthionine-containing lantibiotics (class I) and the non-lanthionine-containing bacteriocins (class II), and which removes the large, heat-labile murein hydrolases (formerly known as class III bacteriocins) to a separate group called bacteriolysins. Recent developments have greatly advanced our understanding of the molecular biology of bacteriocin action and resistance. Highlights include the finding that the class I bacteriocin nisin functions by binding to lipid II — as lipid II is also the target for antibiotics such as vancomycin, this has led to the suggestion that nisin could be used as a template to design novel drugs. Many bacteriocins are produced by food-grade lactic acid bacteria (LAB) and, given that they are also usually heat stable and can inhibit the growth of many of the microorganisms that cause problems in minimally processed foods, they have a host of food microbiology applications. The bacteriocins nisin and pediocin PA1 are already widely used in food preservation. In addition to preventing spoilage, bacteriocins can also be used to improve the quality of foodstuffs, for example, in cheese production, to control the growth of starter cultures and enhance ripening.