ACID-RESISTANT MUTANTS OF LACTOCOCCUS-LAC TIS

In all environments, bacteria are submitted to stress conditions which compromise cell growth and survival. It is now established that bacte ria have inducible stress resistance mechanisms which favor bacterial survival under difficult conditions. These resistance mechanisms may b e useful for improving strain survival in technological processes. Usi ng L. lactis, we selected mutants more resistant to acid stress than t he wildtype strain, MG1363. Results of genetic and phenotypic characte rization of these mutants established that strain survival is improved compared to MG1363 in a single or up to three different stress condit ions, and sometimes by a factor of 2 000. This work shows that in L. l actis, stress responses can overlap and that a mutated strain can be m ore appropriate than the wild-type to survive abrupt environmental cha nges. Such strains may have improved properties in industrial processe s. (C) Inra/Elsevier, Paris.