Different sugar residues of the lipopolysaccharide outer core are required for early interactions of Salmonella enterica serovars Typhi and Typhimurium with epithelial cells
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Bravo, Denisse
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Different sugar residues of the lipopolysaccharide outer core are required for early interactions of Salmonella enterica serovars Typhi and Typhimurium with epithelial cells
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Abstract
The role of lipopolysaccharide (LPS) in entry of Salmonella Typhimurium into epithelial cells remains
unclear. In this study, we tested the ability of a series of mutants with deletions in genes for the synthesis
and assembly of the O antigen and the outer core of LPS to adhere to and invade HeLa, BHK, and IB3
epithelial cells lines. Mutants devoid of O antigen, or that synthesized only one O antigen unit, or with
altered O antigen chain lengths were as able as the wild type to enter epithelial cells, indicating that this
polysaccharide is not required for invasion of epithelial cells in vitro. In contrast, the LPS core plays a role
in the interaction of S. Typhimurium with epithelial cells. The minimal core structure required for
adherence and invasion comprised the inner core and residues Glc IeGal I of the outer core. A mutant of
S. Typhimurium that produced a truncated LPS core lacking the terminal galactose residue had
a significant lower level of adherence to and ingestion by the three epithelial cell lines than did strains
with this characteristic. Complementation of the LPS production defect recovered invasion to parental
levels. Heat-killed bacteria with a core composed of Glc IeGal I, but not bacteria with a core composed of
Glc I, inhibited uptake of the wild type by HeLa cells. A comparison of the chemical structure of
the S. Typhi core with the published chemical structure of that of S. Typhimurium indicated that the
Glc IeGal IeGlc II backbone is conserved in both serovars. However, S. Typhi requires a terminal glucose
for maximal invasion. Therefore, our data indicate that critical saccharide residues of the outer core play
different roles in the early interactions of serovars Typhi and Typhimurium with epithelial cells.
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This workwas supported by grants ADI-08/2006 from CONICYT/
World Bank (to I. C.) and from the Canadian Institutes of Health
Research (to M. A. V.). D. B was supported by a CONICYT Scholarship.
M. A. V. holds a Canada Research Chair in Infectious Diseases
and Microbial Pathogenesis.
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URI: https://repositorio.uchile.cl/handle/2250/121615
DOI: doi:10.1016/j.micpath.2010.11.001
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Microbial Pathogenesis 50 (2011) 70-80
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