Lactobacillus delbrueckii ssp. bulgaricus thermotolerance

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Gouesbet , Gwenola ; Jan , Gwenaël ; Boyaval , Patrick (2001)
  • Publisher: INRA Editions
  • Related identifiers: doi: 10.1051/lait:2001133
  • Subject: protection croisée | osmotic stress | stress osmotique | heat-shock response | thermoadaptation<br>---<br>réponse au stress thermique | thermotolérance | glycine bétaïne | [ SDV.AEN ] Life Sciences [q-bio]/Food and Nutrition | betaine | cross-protection | [ SDV.IDA ] Life Sciences [q-bio]/Food engineering

International audience; Lactobacillus delbrueckii ssp. bulgaricus is a lactic acid bacterium widely used in the dairy food industry. Since the industrial processes are a succession of constraints, it is essential to understand the behaviour of L. bulgaricus when facing usual stresses. The influence of heat stress was investigated on the viability of L. bulgaricus cells grown in a chemically defined medium. The susceptibility of cells to heat-shock was obvious only above 55 $^{\circ}$C. We investigated the acquisition of thermotolerance as a result of exposure to a moderate heat-shock, and the acquisition of a cross-stress-tolerance by exposure to a mild osmotic stress. When cells were submitted, before lethal temperature challenge (65 $^{\circ}$C), to a heat pre-treatment at 50 $^{\circ}$C or to a hyper-osmotic pre-treatment, the viability of cells increased. For the industrial strain RD 546, the addition of glycine betaine (GB) in 0.4 mol.L$^{-1}$ NaCl during the pre-treatment decreased the acquired thermotolerance, while GB alone enhanced cell viability. The thermotolerance of the type strain was not influenced by GB. We demonstrated that the stress tolerance induced by a moderate heat-shock was dependent on protein synthesis, while the effect of GB on RD 546 thermotolerance was independent of such biosynthesis. Thermotolerance acquired in presence of GB depends on a strain-dependant mechanism that differs from the mechanism involved after a moderate heat-shock.; Stress thermique et thermotolérance chez Lactobacillus delbrueckii ssp. bulgaricus . Lactobacillus delbrueckii ssp. bulgaricus est une bactérie lactique largement utilisée en industrie alimentaire. Les procédés industriels étant une succession de contraintes, il est essentiel de connaître le comportement de L. bulgaricus face aux stress rencontrés. L'influence du stress thermique sur la viabilité de 2 souches de L. bulgaricus, cultivées en milieu chimiquement défini, a été étudiée. La viabilité des cellules n'est affectée qu'au-delà de 55 $^{\circ}$C. Les cellules acquièrent une thermotolérance vis-à-vis d'un choc thermique à 65 $^{\circ}$C durant 10 min, c'est-à-dire une viabilité accrue, après exposition à un prétraitement thermique modéré à 50 $^{\circ}$C ou un prétraitement hyperosmotique. Pour la souche industrielle RD 546, l'addition de glycine bétaïne (GB) dans le milieu de prétraitement contenant 0,4 mol.L$^{-1}$ NaCl diminue la thermotolérance acquise, tandis que la glycine bétaïne seule en tant que prétraitement avant le choc létal augmente la viabilité cellulaire. La thermotolérance induite par un prétraitement thermique modéré est dépendante de la synthèse protéique, tandis que l'effet de la GB sur la thermotolérance est indépendant de biosynthèse. La thermotolérance acquise en présence de GB nécessite un mécanisme souche-dépendant distinct par rapport à celui impliqué lors d'un prétraitement thermique.
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