Affiliation:
1. Departments of Microbiology and Immunology
2. Pathology, University of Texas Medical Branch, Galveston, Texas 77555-1070
3. Departments of Medical and Research Technology and Epidemiology and Preventive Medicine, University of Maryland, Baltimore, Maryland 21201
Abstract
ABSTRACT
In this study, we cloned and sequenced a virulence-associated gene (
vacB
) from a clinical isolate SSU of
Aeromonas
hydrophila
. We identified this gene based on our recently annotated genome sequence of the environmental isolate ATCC 7966
T
of
A. hydrophila
and the
vacB
gene of
Shigella flexneri
. The
A. hydrophila
VacB protein contained 798 amino acid residues, had a molecular mass of 90.5 kDa, and exhibited an exoribonuclease (RNase R) activity. The RNase R of
A. hydrophila
was a cold-shock protein and was required for bacterial growth at low temperature. The
vacB
isogenic mutant, which we developed by homologous recombination using marker exchange mutagenesis, was unable to grow at 4°C. In contrast, the wild-type (WT)
A. hydrophila
exhibited significant growth at this low temperature. Importantly, the
vacB
mutant was not defective in growth at 37°C. The
vacB
mutant also exhibited reduced motility, and these growth and motility phenotype defects were restored after complementation of the
vacB
mutant. The
A. hydrophila
RNase R-lacking strain was found to be less virulent in a mouse lethality model (70% survival) when given by the intraperitoneal route at as two 50% lethal doses (LD
50
). On the other hand, the WT and complemented strains of
A. hydrophila
caused 80 to 90% of the mice to succumb to infection at the same LD
50
dose. Overall, this is the first report demonstrating the role of RNase R in modulating the expression of
A. hydrophila
virulence.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
52 articles.
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