Biosynthesis of bacteriocins in lactic acid bacteria.

A large number of new bacteriocins in lactic acid bacteria (LAB) has been characterized in recent years. Most of the new bacteriocins belong to the class II bacteriocins which are small (30-100 amino acids) heat- stable and commonly not post-translationally modified. While most bacteriocin producers synthesize only one bacteriocin, it has been shown that several LAB produce multiple bacteriocins (2-3 bacteriocins). Based on common features, some of the class II bacteriocins can be divided into separate groups such as the pediocin-like and strong anti-listeria bacteriocins, the two-peptide bacteriocins, and bacteriocins with a sec-dependent signal sequence. With the exception of the very few bacteriocins containing a sec-dependent signal sequence, class II bacteriocins are synthesized in a preform containing an N-terminal double-glycine leader. The double-glycine leader-containing bacteriocins are processed concomitant with externalization by a dedicated ABC-transporter which has been shown to possess an N-terminal proteolytic domain. The production of some class II bacteriocins (plantaricins of Lactobacillus plantarum C11 and sakacin P of Lactobacillus sake) have been shown to be transcriptionally regulated through a signal transduction system which consists of three components: an induction factor (IF), histidine protein kinase (HK) and a response regulator (RR). An identical regulatory system is probably regulating the transcription of the sakacin A and carnobacteriocin B2 operons. The regulation of bacteriocin production is unique, since the IF is a bacteriocin-like peptide with a double-glycine leader processed and externalized most probably by the dedicated ABC-transporter associated with the bacteriocin. However, IF is not constituting the bacteriocin activity of the bacterium, IF is only activating the transcription of the regulated class II bacteriocin gene(s). The present review discusses recent findings concerning biosynthesis, genetics, and regulation of class II bacteriocins.