from Takeshi Zendo and Kenji Sonomoto writing in Lactic Acid Bacteria and Bifidobacteria: Current Progress in Advanced Research:
Many strains of lactic acid bacteria produce antimicrobial peptides, bacteriocins, which are expected to be used as safe antimicrobial agents as well as food preservatives. Since nisin A was recognized in 1928, diverse bacteriocins have been identified from various species of lactic acid bacteria. Based on their structures and characteristics, bacteriocins were classified mainly into two classes, class I (lantibiotics) and class II, and new classification schemes are being proposed according to their expanding diversity. Class I bacteriocins represented by nisin A contain posttranslationally modified amino acids such as lanthionine. Class II bacteriocins are further divided into some subclasses such as class IIa (pediocin-like bacteriocins) and class IIb (two-peptide bacteriocins).
Further reading: Lactic Acid Bacteria and Bifidobacteria: Current Progress in Advanced Research