부산대학교 도서관

In all environments, bacteria are submitted to stress conditions which compromise cell growth and survival. It is now established that bacteria have inducible stress resistance mechanisms which favor bacterial survival under difficult conditions. These resistance mechanisms may be useful for improving strain survival in technological processes. Using L lactis, we selected mutants more resistant to acid stress than the wild-type strain, MG1363. Results of genetic and phenotypic characterization of these mutants established that strain survival is improved compared to MG1363 in a single or up to three different stress conditions, and sometimes by a factor of 2 000. This work shows that in L lactis, stress responses can overlap and that a mutated strain can be more appropriate than the wild-type to survive abrupt environmental changes. Such strains may have improved properties in industrial processes. ? Inra / Elsevier, Paris.Dans tout environnement, les bact?ries sont soumises ? des stress qui compromettent la multiplication et la survie de l'esp?ce. Il est d?sormais ?tabli que les bact?ries poss?dent des m?canismes inductibles de r?sistance aux stress qui contribuent ? leur survie en conditions d?favorables. Pour am?liorer la survie des souches en condition technologique, nous avons s?lectionn? des mutants de Lactococcus lactis plus r?sistants au stress acide que la souche sauvage, MG1363. La caract?risation g?n?tique et ph?notypique de ces mutants r?v?le que certaines mutations conf?rent une survie jusqu'? 2 000 fois sup?rieure ? celle de MG1363 dans une, deux ou trois conditions de stress. Cette approche d?montre qu'il existe chez L. lactis des chevauchements entre les m?canismes de r?sistance aux stress et que des mutations ad?quates peuvent conduire ? des souches plus performantes face ? de brusques changements environnementaux. De telles souches pourraient am?liorer le rendement et la reproductibilit? des processus industriels. ? Inra / Elsevier, Paris.