Affiliation:
1. Department of Molecular Biology, Umeå University, S-901 87 Umeå, Sweden
Abstract
ABSTRACT
ToxR, a transmembrane regulatory protein, has been shown to respond to environmental stimuli. To better understand how the aquatic bacterium
Vibrio anguillarum
, a fish pathogen, responds to environmental signals that may be necessary for survival in the aquatic and fish environment,
toxR
and
toxS
from
V. anguillarum
serotype O1 were cloned. The deduced protein sequences were 59 and 67% identical to the
Vibrio cholerae
ToxR and ToxS proteins, respectively. Deletion mutations were made in each gene and functional analyses were done. Virulence analyses using a rainbow trout model showed that only the
toxR
mutant was slightly decreased in virulence, indicating that ToxR is not a major regulator of virulence factors. The
toxR
mutant but not the
toxS
mutant was 20% less motile than the wild type. Like many regulatory proteins, ToxR was shown to negatively regulate its own expression. Outer membrane protein (OMP) preparations from both mutants indicated that ToxR and ToxS positively regulate a 38-kDa OMP. The 38-kDa OMP was shown to be a major OMP, which cross-reacted with an antiserum to OmpU, an outer membrane porin from
V. cholerae
, and which has an amino terminus 75% identical to that of OmpU. ToxR and to a lesser extent ToxS enhanced resistance to bile. Bile in the growth medium increased expression of the 38-kDa OMP but did not affect expression of ToxR. Interestingly, a
toxR
mutant forms a better biofilm on a glass surface than the wild type, suggesting a new role for ToxR in the response to environmental stimuli.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference67 articles.
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Photobacterium profundum
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