JB Accepts, published online ahead of print on 30 October 2009

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Google Scholar Articles by Berger, B. Articles by Arigoni, F. PubMed PubMed Citation Articles by Berger, B. Articles by Arigoni, F.

 Previous Article  |  Next Article 

J. Bacteriol. doi:10.1128/JB.01147-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

HspR Mutations Are Naturally Selected in Bifidobacterium longum When Applying Successive Heat-Shock Treatments.

B. Berger^*, D. Moine, R. Mansourian, and F. Arigoni

Nestlé Research Center, Vers-Chez-Les-Blanc, 1000 Lausanne 26, Switzerland

^* To whom correspondence should be addressed. Email: bernard.berger{at}rdls.nestle.com.

The development of molecular tools allowed to shed light on several widespread genetic mechanisms aiming at limiting the effect of the molecular damages on bacterial survival. For some bacterial taxa, the genetic toolbox is scarce and limits the possibilities to investigate the molecular basis of their stress response. In that case, an alternative strategy is to study genetic variants of a strain under stress conditions. The comparative study of the genetic determinants responsible for their phenotypes, e. g. an improved tolerance to stress, offers precious clues on the molecular mechanisms effective in this bacterial taxon. We applied this approach and isolated two heat-shock tolerant strains derived from Bifidobacterium longum NCC2705. A global analysis of their transcriptomes revealed that in both strains the dnaK operon and the clpB gene were over-expressed. We sequenced the hspR gene coding for the negative regulator of dnaK and clpB, and found point mutations affecting protein domains likely responsible for the binding of the regulators to the promoter DNA. Complementation of the mutant strains by the wt regulator hspR restored its heat-sensitivity and thus demonstrated that these mutations were responsible for the observed heat-tolerance phenotype.