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Infection and Immunity, August 2000, p. 4452-4461, Vol. 68, No. 8
Department of Microbiology and Immunology,
University of Kentucky, Lexington, Kentucky
Received 18 February 2000/Returned for modification 17 April
2000/Accepted 1 May 2000
One prerequisite for the virulence of Yersinia pestis,
causative agent of bubonic plague, is the yersiniabactin (Ybt)
siderophore-dependent iron transport system that is encoded within a
high-pathogenicity island (HPI) within the pgm locus of the
Y. pestis chromosome. Several gene products within the HPI
have demonstrated functions in the synthesis or transport of Ybt. Here
we examine the roles of ybtU and ybtT. In-frame
mutations in ybtT or ybtU yielded strains defective in siderophore production. Mutant strains were unable to grow
on iron-deficient media at 37°C but could be cross-fed by culture
supernatants from a Ybt-producing strain of Y. pestis. The
ybtU mutant failed to express four indicator Ybt proteins (HMWP1, HMWP2, YbtE, and Psn), a pattern similar to those for other
ybt biosynthetic mutants. In contrast, strains carrying mutations in ybtT or ybtS (a previously
identified gene required for Ybt biosynthesis) produced all four
proteins at wild-type levels under iron-deprived conditions. To assess
the effects of ybtT, -U, and -S
mutations on transcription of ybt genes, reporter plasmids
with ybtP or psn promoters controlling
lacZ expression were introduced into these mutants. Normal
iron-regulated
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Yersinia pestis YbtU and YbtT Are
Involved in Synthesis of the Siderophore Yersiniabactin but Have
Different Effects on Regulation

-galactosidase activity was observed in the
ybtT and ybtS mutants, whereas a significant
loss of expression occurred in the
ybtU strain. These results show that ybtT and ybtU genes are
involved in the biosynthesis of the Ybt siderophore and that a
ybtU mutation but not ybtT or ybtS
mutations affects transcription from the ybtP and
psn promoters.
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, MS415 Medical Center, University of
Kentucky, Lexington, KY 40536-0084. Phone: (859) 323-6341. Fax: (859)
257-8994. E-mail: rperry{at}pop.uku.edu.
Formerly Valérie A. Coulanges.
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