Affiliation:
1. Laboratoire de Microbiologie de l'Environnement, USC INRA-EA956, Université de Caen, Caen, France
Abstract
ABSTRACT
Analysis of the genome sequence of
Enterococcus faecalis
allowed the identification of two genes whose protein products showed 33 and 34% identity with those of
sigV
and
yrhM
of
Bacillus subtilis
, respectively. These genes, named
sigV
and
rsiV
, are predicted to encode members of the extracytoplasmic function subfamily of eubacterial RNA polymerase sigma and anti-sigma factors, respectively. This group of sigma factors has been shown to regulate gene expression in response to stress conditions.
sigV
and
rsiV
were shown to be under the control of the same promoter. The transcriptional start site was determined, and the 1.5-kb mRNA transcript was shown to be overexpressed under glucose and complete starvation, as well as under physicochemical treatments. Three mutants, affected in
sigV
,
rsiV
, and both genes, were constructed by double-crossover recombination within the genome of
E
.
faecalis
strain JH2-2. Compared with the wild type and the
rsiV
mutant, the
sigV
mutants were more susceptible to heat shock, acid, and ethanol treatments and displayed decreased survival during long-term starvation. A nisin-inducible
sigV
gene construction used in complementation assays restored the wild phenotype of the
sigV
mutants, confirming the involvement of SigV in the heat shock, ethanol, and acid stress responses. Northern blot analysis carried out with the three mutant strains revealed the inhibition of
sigV
expression by the related anti-sigma factor gene
rsiV
. In addition, putative candidates of the
sigV
regulon determined by computer search for the
sigV
promoter sequence were analyzed.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
57 articles.
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