The acid tolerance response of Bacillus cereus ATCC14579 is dependent on culture pH, growth rate and intracellular pH
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The food pathogen Bacillus cereus is likely to encounter acidic environments (i) in food when organic acids are added for preservation purposes, and (ii) during the stomachal transit of aliments. In order to characterise the acid stress response of B. cereus ATCC14579, cells were grown in chemostat at different pH values (pHo from 9.0 to 5.5) and different growth rates (μ from 0.1 to 0.8 h−1), and were submitted to acid shock at pH 4.0. Cells grown at low pHo were adapted to acid media and induced a significant acid tolerance response (ATR). The ATR induced was modulated by both pHo and μ, and the μ effect was more marked at pHo 5.5. Intracellular pH (pHi) was affected by both pHo and μ. At a pHo above 6, the pHi decreased with the decrease of pHo and the increase of μ. At pHo 5.5, pHi was higher compared to pHo 6.0, suggesting that mechanisms of pHi homeostasis were induced. The acid survival of B. cereus required protein neo-synthesis and the capacity of cells to maintain their pHi and ΔpH (pHi - pHo). Haemolysin BL and non-haemolytic enterotoxin production were both influenced by pHo and μ.
KeywordsBacillus cereus Chemostat Acid tolerance response Stress Intracellular pH
Acid tolerance response
Carboxyfluorescein diacetate succinimidyl ester
Carboxyfluorescein succinimidyl ester
General linear model
Honest significant difference
We are grateful to Claire Dargaignaratz for her technical assistance. This work was supported by the Ministère de l’Education Nationale, de l’Enseignement Supérieur et de la Recherche (French Ministry for Education and Research).
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