Acid sensitivity of neomycin-resistant mutants of Oenococcus oeni: a relationship between reduction of ATPase activity and lack of malolactic activity

Mutants of Oenococcus oeni were isolated as spontaneous neomycin-resistant mutants. three of these mutants harbored a significantly reduced ATPase act ivity that represented 50% of that of the wild-type strain. Their growth ra tes were also impaired at pH 5.3 (46-86% of the wild-type level). However, the profiles of sugar consumption appeared identical to those of the parent al strain. At pH 3.2, all the mutant strains failed to grow and a drastic d ecrease in viability was observed after an acid shock. Surprisingly, all th e isolated mutants were devoid of malolactic activity. These results sugges t that the ATPase and malolactic activities of O. oeni are linked to each o ther and play a crucial role in the mechanism of resistance to an acid stre ss. (C) 1999 Federation of European Microbiological Societies.