acetophilic strains that grow only at a pH value of about 3.5, acetophobic strains that only grow at pH levels higher than 6.5, and acetotolerant strains that can grow at both these values. There may be a gradual development from acetophobic to acetotolerant strains and, with prolonged exposure to low pH and high acetic acid concentrations, to acetophilic strains. This suggests the development of a gradual acid resistance in these bacteria