POSTERS - BLAST X - University of Utah

BLAST X Poster #29
THE HELICOBACTER PYLORI FLAGELLAR ANTI-SIGMA FACTOR FlgM REMAINS
BACTERIA-ASSOCIATED AND INTERACTS WITH FlhAC
Melanie Rust 1 , Sophie Borchert 1 , Eugenia Gripp 1 , Sarah Kühne 1 , Eike Niehus 1 , Sebastian
Suerbaum 1 , Kelly T. Hughes 2 , Christine Josenhans 1
1 Department for Med. Microbiology and Hospital Epidemiology, Hannover Medical School ,Carl-
Neuberg-Strasse 1, D-30625 Hannover, Germany, 2 Department of Biology, University of Utah,
USA
Helicobacter pylori persistently colonize in the human gastric mucus with the help of their
polar flagellar organelles. A particular feature of flagella in most Helicobacter species including
H. pylori is the presence of a membraneous flagellar sheath. Previously, flagellar regulators
FliA, RpoN and the functional master regulator FlhA were characterized. H. pylori also
possesses an anti-sigma factor FlgM, which has an unusually short N-terminus, yet is functional
in Salmonella. FlgM in H. pylori fulfills a similar conserved function as an antagonist and binding
partner to FliA. However, FlgM of H. pylori is unusual, since it lacks an N-terminal domain
present in other FlgM homologs, e.g. FlgM of Salmonella, whose function is intimately coupled
to its secretion through the flagellar type III secretion system.
The aim of the present study was to characterize in more detail the localization and
potential for secretion of the short H. pylori FlgM in the presence of a flagellar sheath.
Furthermore we investigated its interaction with other flagellar proteins in the basal body, which
may be required for its function in flagellar regulation. FlgM was expressed in flhA mutants and
was differentially localized in bacterial fractions of flhA mutant bacteria in comparison to wild
type bacteria. H. pylori FlgM was only released into the medium in very minor amounts in wild
type bacteria, where the bulk amount of the protein was retained in the cytoplasm, and some
FlgM was detected in the flagellar fraction. FlgM-GFP (green fluorescent protein) and FlgM-V5
translational fusions were generated and expressed in H. pylori. FlgM displayed a
predominantly polar distribution in microscopy. Evidence was gathered that it is able to interact
with the C-terminal domain of the flagellar basal body protein FlhA. We conclude that in H. pylori
and possibly in other closely related bacteria, which also possess a truncated FlgM, secretion
may not be paramount for the regulatory function of FlgM and that protein interactions at the
flagellar basal body, in particular with FlhAC, may determine the turnover and localization of
functional FlgM in H. pylori.
We gratefully acknowledge the German Research Council, grant Jo344/2-2, for financial
support.
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