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Appl Environ Microbiol. 2007 Jun;73(12):3924-35. Epub 2007 Apr 20.

The early response to acid shock in Lactobacillus reuteri involves the ClpL chaperone and a putative cell wall-altering esterase.

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  • 1Department of Microbiology, Swedish University of Agricultural Sciences, Box 7025, SE-750 07 Uppsala, Sweden, and Department of Pathology, Texas Children's Hospital, Houston, TX 77030, USA.


To be able to function as a probiotic, bacteria have to survive the passage through the gastrointestinal tract. We have examined survival and gene expression of Lactobacillus reuteri ATCC 55730 after a sudden shift in environmental acidity to a pH close to the conditions in the human stomach. More than 80% of the L. reuteri cells survived at pH 2.7 for 1 h. A genomewide expression analysis experiment using microarrays displayed 72 differentially expressed genes at this pH. The early response to severe acid shock in L. reuteri differed from long-term acid adaptation to milder acid stress studied in other lactic acid bacteria. The genes induced included the following: clpL, genes putatively involved in alterations of the cell membrane and the cell wall; genes encoding transcriptional regulators; phage genes; and genes of unknown function. Two genes, clpL, encoding an ATPase with chaperone activity, and lr1516, encoding a putative esterase, were selected for mutation analyses. The mutants were significantly more sensitive to acid than the wild type was. Thus, these genes could contribute to the survival of L. reuteri in the gastrointestinal tract.

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