Affiliation:
1. Department of Molecular Microbiology, Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 63110
Abstract
ABSTRACT
Pathogenicity islands are chromosomal clusters of pathogen-specific virulence genes often found at tRNA loci. We have determined the molecular genetic structure of SPI-3, a 17-kb pathogenicity island located at the
selC
tRNA locus of
Salmonella enterica
serovar Typhimurium. The G+C content of SPI-3 (47.5%) differs from that of the
Salmonella
genome (52%), consistent with the notion that these sequences have been horizontally acquired. SPI-3 harbors 10 open reading frames organized in six transcriptional units, which include the previously described
mgtCB
operon encoding the macrophage survival protein MgtC and the Mg
2+
transporter MgtB. Among the newly identified open reading frames, one exhibits sequence similarity to the ToxR regulatory protein of
Vibrio cholerae
and one is similar to the AIDA-I adhesin of enteropathogenic
Escherichia coli
. The distribution of SPI-3 sequences varies among the salmonellae: the right end of the island, which harbors the virulence gene
mgtC
, is present in all eight subspecies of
Salmonella
; however, a four-gene cluster at the center of SPI-3 is found in only some of the subspecies and is bracketed by remnants of insertion sequences, suggesting a multistep process in the evolution of SPI-3 sequences.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
167 articles.
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