La réponse au stress osmotique des bactéries lactiques Lactococcus lactis et Lactobacillus plantarum (mini-revue)

Abstract

-Osmotic stress response of lactic acid bacteria Lactococcus lactis and Lactobacillus plantarum. In order to survive in a wide variety of environments, bacteria have evolved systems that protect themselves against environmental stress. Lactic acid bacteria grow in media where osmolarity is high and varies frequently and they must adjust their intracellular osmolarity in order to maintain the turgor pressure necessary for cell elongation. An osmotic upshock stops their growth and activates specific mechanisms which prevent cells death. The regulatory mechanisms of the response of Lactococcus lactis and Lactobacillus plantarum to an osmotic stress have drawn increasing attention in recent years, because of their use in industrial fermentations and their fundamental interest as Gram positive bacteria. The main response to osmotic stress is the accumulation in the cytoplasm of osmoprotectant organic compounds, the so-called "compatible solutes", which can accumulate to very high levels without deleterious effects on the cellular metabolism. In this review, we present the state of the art on the physiological and molecular responses of L. lactis and L. plantarum to an osmotic stress. osmotic regulation / lactic acid bacteria / stress / ABC transporter Résumé -Les bactéries sont capables de vivre dans des milieux extrêmement variés car elles possèdent des systèmes de protection efficaces contre les différents stress qu'elles peuvent rencontrer. Les bactéries lactiques vivent dans des habitats où l'osmolarité est souvent élevée et varie énormé-ment, alors que la pression osmotique intracellulaire doit rester relativement constante. Lorsqu'une bactérie subit un stress osmotique, dû à une forte augmentation de la concentration en sel dans l'environnement, sa croissance est arrêtée, et des mécanismes de détresse se mettent en place pour éviter la mort cellulaire. Les études sur la réponse au stress osmotique des bactéries lactiques Lactococcus lactis et Lactobacillus plantarum et les mécanismes moléculaires sous-jacents se sont développées depuis ces dernières années, du fait de l'intérêt économique (utilisation dans l'industrie agroalimentaire) et fondamental (bactéries à Gram positif) que représentent ces organismes. La principale réponse à un choc osmotique consiste en l'accumulation dans le cytoplasme de molécules protectrices, Lait 81 (2001) [49][50][51][52][53][54][55] 49

Adaptation to high salt in Lactobacillus: role of peptides and proteolytic enzymes

“…In that case, QacT transcription was semi‐constitutively maintained but upon osmotic up shift enzymatic activity increased (Glaasker et al. 1998; Romeo et al. 2001).…”

“…Compatible solutes do not interfere with macromolecules and allow the maintenance of high levels of cellular function (Csonka and Hanson 1991). The main compatible solute actually described in LAB is glycine–betaine (Romeo et al. 2001).…”

Genome Sequence of Lactobacillus plantarum Strain UCMA 3037

“…The products of some genes are found to confer an advantage for adaptation to a cheese matrix; for example, malate lactate dehydrogenase (4) and histidine kinase for resistance to an acidic environment (5), two types of glycine/betaine transporter for osmoregulation (6), lipase/esterases for the production of cheese flavor compounds (7), and the serine protease HtrA domain (putative caseinase) (8). …”

Effect of water activity and protective solutes on growth and subsequent survival to air-drying of Lactobacillus and Bifidobacterium cultures

“…Since many lactic cultures cannot synthesize these compounds, they are generally absorbed from the exocellular environment (Romeo et al 2001). In this respect, betaine accumulation has been the most widely studied (Guillot et al 2000;Linders et al 1997b).…”

“…There are numerous reports on the effect of protective solutes during an osmotic stress on L. plantarum (Romeo et al 2001) and lactococci (Sanders et al 1999), but little data are available for probiotic bacteria such as Lactobacillus rhamnosus, Lactobacillus acidophilus, L. casei or Bifidobacterium.…”