Acid tolerance response is low-pH and late-stationary growth phase inducible in Bacillus cereus TZ415

The acid tolerance of foodborne pathogen Bacillus cereus TZ415 was examined. B. cereus was more tolerant to an acid challenge at pH 4.0 when cells were grown at low pH in regulated batch cultures of rich J Broth (JB) medium. The pH-inducible acid tolerance response (ATR) was maximal at pH 5.0, a sublethal growth condition inducing a remarkable cell elongation. During growth at regulated pH 7.0 and 6.0, B. cereus TZ415 became more acid sensitive from lag to stationary growth phase and the acid tolerance of cells reached its maximum level in late-stationary growth phase. The ATR induced at pH 5.5 and 5.0 was not affected by growth phase. Cellular protein profiles were analysed as a function of growth phase and medium pH. The Hemolysin BL (HBL) enterotoxin was only detected when cells were grown at pH 7.0.