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Infection and Immunity, June 2000, p. 3368-3376, Vol. 68, No. 6
Department of Microbiology, University of
Iowa School of Medicine, Iowa City, Iowa 52242-1109
Received 20 December 1999/Returned for modification 18 February
2000/Accepted 24 March 2000
Salmonella enterica serovar Typhimurium initiates
infection of a host by inducing its own uptake into specialized M cells which reside within the epithelium overlaying Peyer's patches. Entry
of Salmonella into intestinal epithelial cells is dependent upon invasion genes that are clustered together in
Salmonella pathogenicity island 1 (SPI-1). Upon contact
between serovar Typhimurium and epithelial cells targeted for bacterial
internalization, bacterial proteins are injected into the host cell
through a type III secretion system that leads to internalization of
the bacteria. Previous work has established that the prgH,
-I, -J, and -K and orgA
genes reside in SPI-1, and the products of these genes are predicted to
be components of the invasion secretion apparatus. We report that an
error in the published orgA DNA sequence has been
identified so that this region encodes two small genes rather than a
single large open reading frame. These genes have been designated
orgA and orgB. Additionally, an opening reading
frame downstream of orgB, which we have designated
orgC, has been identified and partially characterized.
Previously published work has indicated that the prgH,
-I, -J, and -K genes are
transcribed from a promoter distinct from that used by the gene
immediately downstream, orgA. Here, we present experiments
indicating that orgA expression is driven by the
prgH promoter. In addition, using reverse transcriptase PCR
analysis, we have found that this polycistronic message extends downstream of prgH to include a total of 10 genes. To more
fully characterize this invasion operon, we demonstrate that the
prgH, prgI, prgJ, prgK,
orgA, and orgB genes are each required for
invasion and secretion, while orgC is not essential for the
invasive phenotype.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Transcriptional Organization and Function of
Invasion Genes within Salmonella enterica Serovar
Typhimurium Pathogenicity Island 1, Including the prgH,
prgI, prgJ, prgK, orgA,
orgB, and orgC Genes
*
Corresponding author. Mailing address: Department of
Microbiology, University of Iowa College of Medicine, 3-330 Bowen
Science Bldg., Iowa City, IA 52242. Phone: (319) 353-5457. Fax: (319) 335-9006. E-mail: bjones{at}blue.weeg.uiowa.edu.
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