ACID TOLERANCE IN LEUCONOSTOC-OENOS - ISOLATION AND CHARACTERIZATION OF AN ACID-RESISTANT MUTANT

The acid tolerance of Leuconostoc oenos was examined in cells survivin g at pH 2.6, which is lower than the acid limit of growth (about pH 3. 0). Acid-adapted cells survived better than non-adapted cells. Toleran ce to acid stress was found to be dependent upon the adaptive pH. Acid resistance was increased by an order of magnitude for cultures adapte d to a pH of about 2.9. Inhibiting protein synthesis with chlorampheni col prior to acid shock revealed that acid adaptation may involve two separate systems, one of which appears to be independent of protein sy nthesis. The acid-resistant mutant LoV8413, isolated during a longterm survival screen at pH 2.6, was found to be able to grow in acidic med ia and was characterized by a high H+-ATPase activity at low pH. The d ata from electrophoretic analysis of total proteins labeled with [S-35 ]methionine indicate that large amounts of a protein of 42 kDa molecul ar mass were produced within this acid-resistant mutant.