INDUCED ACID TOLERANCE IN LISTERIA-MONOCYTOGENES

Growth of Listeria monocytogenes at pH 5.0 did not increase growth of the organism at pH 7.0 after exposure to low pH (3.0, 3.5), compared with cells initially grown at pH 7.0. However, growth at pH 5.0 significantly increased the survival of cells at low pH as determined by plate counts compared with cells grown at neutral pH. Thus, pH adaptation not only occurs in enteric bacteria but also in this Gram-positive organism. Alterations in the cytoplasmic membrane could be responsible.