Characterization of the protein-synthesis dependent adaptive acid tolerance response in Lactobacillus acidophilus

Exposure of L. acidophilus CRL 639 cells to sublethal adaptive acid conditions (pH 5.0 for 60 min) was found to confer protection against subsequent exposure to lethal pH (pH 3.0). Adaptation, which only occurred in complex media, was dependent on de novo protein synthesis and was inhibited by amino acid analogues. There was no modification in the protein synthesis rate during adaptation, but the protein degradation rate decreased. Synthesis of acid stress proteins may increase the stability of pre-existing proteins. By 2D-PAGE, induction of nine acid stress proteins and repression of several housekeeping proteins was observed. Putative heat shock proteins DnaK, DnaJ, GrpE, GroES and GroEL (70, 43, 24, 10 and 55 kDa, respectively) were among the proteins whose synthesis was induced in response to acid adaptation.