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Journal of Bacteriology, January 2001, p. 611-620, Vol. 183, No. 2
Department of Microbiology, University of
Illinois, Urbana, Illinois 61801
Received 1 August 2000/Accepted 27 October 2000
The lambdoid phage Gifsy-2 contributes significantly to
Salmonella enterica serovar Typhimurium virulence. The
phage carries the periplasmic superoxide dismutase gene,
sodCI, and other unidentified virulence factors. We have
characterized the gene grvA, a single open reading frame
inserted in the opposite orientation in the tail operon of the Gifsy-2
phage. Contrary to what is observed with classic virulence genes,
grvA null mutants were more virulent than wild type as
measured by intraperitoneal competition assays in mice. We have termed
this effect antivirulence. Wild-type grvA in single copy
complemented this phenotype. However, grvA+
on a multicopy plasmid also conferred the antivirulence phenotype. Neither a grvA null mutation nor the
grvA+ plasmid conferred a growth advantage
or disadvantage in laboratory media. The antivirulence phenotype
conferred by the grvA null mutation and the
grvA+ plasmid required wild-type
sodCI but was independent of other virulence factors
encoded on Gifsy-2. These results suggest that in a wild-type
situation, GrvA decreases the pathogenicity of serovar Typhimurium in
the host, most likely by affecting resistance to toxic oxygen species.
These virulence phenotypes were independent of functional Gifsy-2 phage
production. Our data suggest that the contribution of Gifsy-2 is a
complicated sum of both positive virulence factors such as
sodCI and antivirulence factors such as
grvA.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.2.611-620.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Characterization of grvA, an
Antivirulence Gene on the Gifsy-2 Phage in Salmonella
enterica Serovar Typhimurium
*
Corresponding author. Mailing address: Department of
Microbiology, University of Illinois, B103 Chemical and Life Sciences Laboratory, 601 S. Goodwin Ave., Urbana, IL 61801. Phone: (217) 244-1956. Fax: (217) 244-6697. E-mail: j-slauch{at}uiuc.edu.
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