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Infection and Immunity, January 1999, p. 350-356, Vol. 67, No. 1
Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services
University of the Health Sciences, Bethesda, Maryland 20814-4799
Received 5 June 1998/Returned for modification 23 July
1998/Accepted 6 October 1998
Unipolar localization of IcsA on the surface of Shigella
flexneri is required for efficient formation of actin tails and
protrusions in infected eucaryotic cells. Lipopolysaccharide (LPS)
mutations have been demonstrated to affect either the establishment or
the maintenance of IcsA in a unipolar location, although the mechanism is unknown. In order to analyze the contribution of virulence plasmid
determinants on the unipolar localization of IcsA, we examined the
localization of IcsA expressed from a cloned plasmid copy in two
different genetic backgrounds. The localization of IcsA was first
examined in a virulence plasmid-cured derivative of the wild-type
S. flexneri 2a isolate 2457T. This approach examined the
contribution of virulence plasmid-borne factors, including the
previously identified virulence plasmid-borne protease that is
responsible for cleaving IcsA in the outer membrane and releasing the
95-kDa secreted form from the cell surface. IcsA localization in a
related but nonpathogenic Escherichia coli strain
expressing LPS of the O8 serotype was also examined. IcsA surface
presentation in both of these genetic backgrounds continued to be
unipolar, demonstrating that virulence plasmid-borne determinants are
not responsible for unipolar localization of IcsA. The unipolar
localization of IcsA in the E. coli background suggests
that a common pathway that allows IcsA to be spatially restricted to
one pole on the bacterial cell surface exists in Shigella
and E. coli.
0019-9567/99/$00.00+0
Establishment of Unipolar Localization of IcsA in Shigella
flexneri 2a Is Not Dependent on Virulence Plasmid
Determinants
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, Uniformed Services University of the
Health Sciences, F. Edward Hébert School of Medicine, 4301 Jones
Bridge Rd., Bethesda, MD 20814-4799. Phone: (301) 295-3415. Fax: (301) 295-1545. E-mail address: AMAURELLI{at}MXB.USUHS.MIL.
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