EVIDENCE THAT DISSIPATION OF PROTON MOTIVE FORCE IS A COMMON MECHANISM OF ACTION FOR BACTERIOCINS AND OTHER ANTIMICROBIAL PROTEINS

While bacteriocins from lactic acid bacteria (LAB) have generated trem endous interest among food microbiologists, they are not unique. The b iosphere is awash with antimicrobial proteins such as colicins, defens ins, cecropins, and magainins. These proteins share many characteristi cs. They are low molecular weight, cationic, amphiphilic, tend to aggr egate and are benign to the producing organism. In cases where the mod e of action has been investigated, the cell membrane appears to be the site of action. There is increasing evidence that bacteriocins from m any bacterial genera also share these characteristics. After a brief i ntroduction on the significance of LAB bacteriocins, this review provi des some background on proton motive force. Current studies of mechani sms for various bacteriocins are reviewed. Evidence is then introduced that bacteriocins produced by lactic acid bacteria act by the common mechanism of depleting proton motive force. The role and importance of energized membranes in this process is examined. These observations a re linked to literature which demonstrates that many other classes of antimicrobial proteins act by the same mechanism. Questions regarding the role of receptor proteins and the physical mechanism by which PMF is depleted remain unresolved.