BIOSYNTHESIS OF BACTERIOCINS IN LACTIC-ACID BACTERIA

A large number of new bacteriocins in lactic acid bacteria (LAB) has b een characterized in recent years. Most of the new bacteriocins belong to the class II bacteriocins which are small (30-100 amino acids) hea t-stable and commonly not post-translationally modified. While most ba cteriocin producers synthesize only one bacteriocin, it has been shown that several LAB produce multiple bacteriocins (2-3 bacteriocins). Ba sed on common features, some of the class II bacteriocins can be divid ed into separate groups such as the pediocin-like and strong anti-list eria bacteriocins, the two-peptide bacteriocins, and bacteriocins with a sec-dependent signal sequence. With the exception of the very few b acteriocins containing a sec-dependent signal sequence, class II bacte riocins are synthesized in a preform containing an N-terminal double-g lycine leader. The double-glycine leader-containing bacteriocins are p rocessed concomitant with externalization by a dedicated ABC-transport er which has been shown to possess an N-terminal proteolytic domain. T he production of some class II bacteriocins (plantaricins of Lactobaci llus plantarum C11 and sakacin P of Lactobacillus sake) have been show n to be transcriptionally regulated through a signal transduction syst em which consists of three components: an induction factor (IF), histi dine protein kinase (HK) and a response regulator (RR). An identical r egulatory system is probably regulating the transcription of the sakac in A and carnobacteriocin 132 operons. The regulation of bacteriocin p roduction 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, I F is not constituting the bacteriocin activity of the bacterium, IF is only activating the transcripion of the regulated class II bacterioci n gene(s).The present review discusses recent findings concerning bios ynthesis, genetics, and regulation of class II bacteriocins.