Free access article

Lait 78 (1998) 157-163
DOI: 10.1051/lait:1998119

Mutants de Lactococcus lactis résistants à l'acidité

Fabien Rallu, Alexandra Gruss and Emmanuelle Maguin

Laboratoire de génétique microbienne, lnra, 78352 Jouy-en Josas cedex, France

Abstract - Acid-resistant mutants of Lactococcus lactis
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.

Résumé - Dans tout environnement, les bactéries sont soumises à des stress qui compromettent la multiplication et la survie de l'espèce. Il est désormais établi que les bactéries possèdent des mécanismes inductibles de résistance aux stress qui contribuent à leur survie en conditions défavorables. Pour améliorer la survie des souches en condition technologique, nous avons sélectionné des mutants de Lactococcus lactis plus résistants au stress acide que la souche sauvage, MG1363. La caractérisation génétique et phénotypique de ces mutants révèle que certaines mutations confèrent une survie jusqu'à 2 000 fois supérieure à celle de MG1363 dans une, deux ou trois conditions de stress. Cette approche démontre qu'il existe chez L. lactis des chevauchements entre les mécanismes de résistance aux stress et que des mutations adéquates peuvent conduire à des souches plus performantes face à de brusques changements environnementaux. De telles souches pourraient améliorer le rendement et la reproductibilité des processus industriels. © Inra / Elsevier, Paris.

Key words: acid stress / Lactococcus lactis / acid-resistance / multi-stress resistance / transposition

Mots clés : stress acide / Lactococcus lactis / résistance à l'acidité / résistance multiple / transposition

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