Biodiversity of lactic acid bacteria and the effects on their cell surfaceproteinases.

Lactic acid bacteria are used in a wide range of food fermentations and pla y an important role in food industry. The development of molecular biology techniques has revealed a broad genetic diversity and has resulted in a new classification. Lactic acid bacteria associated with food belong to eleven genera: Carnobacterium, Enterococcus, Lactobacillus, Lactococcus, Leuconos toc, Oenococcus, Pediococcus, Streptococcus, Tetragenococcus, Vagococcus et Weissella. This biodiversity is reflected in the properties of a protein a ssuming an identical fonction among these bacteria: the cell surface protei nase. This endoprotease is essential to a rapid bacterial growth in milk an d is responsible for the first step of casein hydrolysis. A variation of th e hydrolysis specificity towards caseins is observed among proteinases from lactococci and lactobacilli. The genetic diversify within Lactobacillus ge nus has generated proteinases with different mechanisms controlling their b iosynthesis, their enzyme maturation and cell wall attachment.