[Implication of quorum sensing phenomenon in the expression of genes that code for bacteriocines in lactic bacteria].

Bacterial Quorum sensing and response or simply quorum sensing (QS) is an ubiquitous regulatory mechanism that allows a continuous monitoring of the cell density in bacterial communities and adequate responses/behaviour to the cellular density. Each cell in these communities produces and responds to a signalling molecule that belongs to some different compounds family: acyl-homoserine-lactones (Gram negative bacteria), oligopeptides (Gram positive bacteria), A12 family (present in both Gram positive and Gram negative bacteria). For an efficient colonization and adaptation to different environmental conditions, lactic acid bacteria require complex sensor systems for the specific detection of the external signals. This function is mediated by the two component regulatory system composed of a histidine protein kinase (HK) with cell-membrane localisation that senses external signals, and a cytoplasmic response regulator (RR), that directly modulates the genome expression. Lactic acid bacteria synthesize bacteriocins depending on the cell density and thus implicating a QS regulatory mechanism. Bacteriocin production is an inducible mechanism that require an extracellular accumulation of some peptides, called peptide inductors, that function as an chemical messenger that activate the bacteriocin synthesis following the QS regulatory pathway.