Abstract
Bacillus spp. produce various types of bacteriocins with different molecular weights from 800 Dalton to 950 kilo Dalton. Several Bacillus bacteriocins belong to the lantibiotics that are the best-described antimicrobial peptides with regard to biosynthesis mechanisms, genetic determinants, and peptide structure. Some Bacillus species produce unmodified bacteriocins including pediocin-like bacteriocins and the two-peptide bacteriocins, while others show completely novel peptide sequences. Some of the well-described bacteriocins produced by Bacillus spp. are subtilin, cerein, bacillocin 490, haloduracin, thuricin, subtilosin, and megacin, all of which are mostly active against Gram-positive bacteria such as Streptococcus, Staphylococcus, Leuconostoc, Listeria, and Gardnerella. This chapter addressed an overview of the diverse classes of bacteriocins produced by bacilli, an update on the efficiency of fish gut-associated Bacillus spp. toward bacterial fish pathogens, and their prospective future applications in aquaculture sector.