Antimicrobial peptides produced by microorganisms

Antimicrobial peptides comprise a diverse group of ribosomally synthesized molecules that include plant thionins and defensins, insect defensins and cecropins, amphibian magainins and temporins, defensins and cathelicidins from higher vertebrates, as well as fungal defensins, cyanobactins, and bacteriocins. The latter are produced by species of bacteria and certain strains of the Archaea domain, being active in small concentrations, and exhibiting bactericidal or bacteriostatic activity against both human and veterinary pathogens. Nisin is the most well-known bacteriocin and the only one approved for use as food preservative; its mechanism of action is based on the interaction with lipid II, a key molecule in the bacterial cell wall synthesis. Although bacteriocins are traditionally used in the food industry, they show several desired features to biotechnological applications, and they could be used in combined therapy or as substitutes of conventional antibiotics in the control of bacterial infections. Although less documented when compared to antibiotics, the issue of resistance among previously sensitive bacterial strains has to be considered for antimicrobial peptides produced by microorganisms. In this chapter, we discuss some relevant concerns regarding the antimicrobial peptides produced by microorganisms, giving special emphasis to the bacteriocins.