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Infection and Immunity, August 2000, p. 4523-4530, Vol. 68, No. 8
Department of Microbiology and Immunology,
Chandler Medical Center, University of Kentucky, Lexington,
Kentucky 40536-0298
Received 16 February 2000/Returned for modification 5 April
2000/Accepted 5 May 2000
The causative agent of plague, Yersinia pestis, is
regarded as being noninvasive for epithelial cells and lacks the major adhesins and invasins of its enteropathogenic relatives Yersinia enterocolitica and Yersinia pseudotuberculosis.
However, there are studies indicating that Y. pestis
invades and causes systemic infection from ingestive and aerogenic
routes of infection. Accordingly, we developed a gentamicin protection
assay and reexamined invasiveness of Y. pestis for HeLa
cells. By optimizing this assay, we discovered that Y. pestis is highly invasive. Several factors, including the
presence of fetal bovine serum, the configuration of the tissue culture
plate, the temperature at which the bacteria are grown, and the
presence of the plasminogen activator protease Pla-encoding plasmid
pPCP1, were found to influence invasiveness strongly. Suboptimal
combinations of these factors may have contributed to negative findings
by previous studies attempting to demonstrate invasion by Y. pestis. Invasion of HeLa cells was strongly inhibited by
cytochalasin D and modestly inhibited by colchicine, indicating strong
and modest respective requirements for microfilaments and microtubules.
We found no significant effect of the iron status of yersiniae or of
the pigmentation locus on invasion and likewise no significant effect
of the Yops regulon. However, an unidentified thermally induced
property (possibly the Y. pestis-specific capsular protein
Caf1) did inhibit invasiveness significantly, and the plasmid pPCP1,
unique to Y. pestis, was essential for highly efficient invasion. pPCP1 encodes an invasion-promoting factor and not just an
adhesin, because Y. pestis lacking this plasmid still
adhered to HeLa cells. These studies have enlarged our picture of
Y. pestis biology and revealed the importance of properties
that are unique to Y. pestis.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Invasion of Epithelial Cells by Yersinia
pestis: Evidence for a Y. pestis-Specific
Invasin
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, Chandler Medical Center, University of
Kentucky, Lexington, KY 40536-0298. Phone: (859) 323-6538. Fax: (859)
257-8994. E-mail: scstra01{at}pop.uky.edu.
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