Nisin is an antimicrobial peptide produced by Gram-positive bacteria that contain unusual dehydrated amino acids and lanthionine rings. Aim: These atypical modifications are added posttranslationally. Nisin, produced by Lactococcus lactis, is the best studied lantibiotic which is widely used for preserving food (E234). Nisin has potent antimicrobial activity against some strains of Gram-positive bacteria. It is synthesized ribosomally and maturated by modification enzymes. NisB dehydrates serines and threonines to dehydroalanine and dehydrobutyrine, respectively. Dehydrated residues are coupled with cysteines by NisC to generate lanthionine rings. Modified nisin is transported by the dedicated ABC transporter NisT and the nisin leader peptide is extracellulary cleaved off by NisP.