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Infection and Immunity, December 2009, p. 5458-5470, Vol. 77, No. 12
0019-9567/09/$08.00+0     doi:10.1128/IAI.00871-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Effect of the O-Antigen Length of Lipopolysaccharide on the Functions of Type III Secretion Systems in Salmonella enterica{triangledown}

Stefanie U. Hölzer,1 Markus C. Schlumberger,2 Daniela Jäckel,1 and Michael Hensel1*

Mikrobiologisches Institut, Universitätsklinikum Erlangen, Erlangen, Germany,1 Institut für Mikrobiologie, ETH Zürich, Switzerland2

Received 2 August 2009/ Returned for modification 29 August 2009/ Accepted 14 September 2009

The virulence of Salmonella enterica critically depends on the functions of two type III secretion systems (T3SS), with the Salmonella pathogenicity island 1 (SPI1)-encoded T3SS required for host cell invasion and the SPI2-T3SS enabling Salmonella to proliferate within host cells. A further T3SS is required for the assembly of the flagella. Most serovars of Salmonella also possess a lipopolysaccharide with a complex O-antigen (OAg) structure. The number of OAg units attached to the core polysaccharide varies between 16 and more than 100 repeats, with a trimodal distribution. This work investigated the correlation of the OAg length with the functions of the SPI1-T3SS and the SPI2-T3SS. We observed that the number of repeats of OAg units had no effect on bacterial motility. The interaction of Salmonella with epithelial cells was altered if the OAg structure was changed by mutations in regulators of OAg. Strains defective in synthesis of very long or long and very long OAg species showed increased translocation of a SPI1-T3SS effector protein and increased invasion. Invasion of a strain entirely lacking OAg was increased, but this mutant strain also showed increased adhesion. In contrast, translocation of a SPI2-T3SS effector protein and intracellular replication were not affected by modification of the OAg length. Mutant strains lacking the entire OAg or long and very long OAg were highly susceptible to complement killing. These observations indicate that the architecture of the outer membrane of Salmonella is balanced to permit sufficient T3SS function but also to confer optimal protection against antimicrobial defense mechanisms.

* Corresponding author. Present address: Abteilung Mikrobiologie, Fachbereich Biologie/Chemie, Universität Osnabrück, Barbarastr. 11, D-49076 Germany. Phone: 49 541 99693940. Fax: 49 541 9693 942. E-mail: Michael.Hensel{at}biologie.uni-onasbrueck.de

{triangledown} Published ahead of print on 21 September 2009.

Editor: A. J. Bäumler

Infection and Immunity, December 2009, p. 5458-5470, Vol. 77, No. 12
0019-9567/09/$08.00+0     doi:10.1128/IAI.00871-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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