POSTERS - BLAST X - University of Utah

BLAST X Poster #59
CHARACTERIZATION OF FliZ AS AN ACTIVATOR OF FLAGELLAR GENES IN
SALMONELLA ENTERICA SEROVAR TYPHIMURIUM
Supreet Saini 1 , Phillip Aldridge 2,3 , and Christopher Rao 1
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-
Champaign, Urbana, Illinois 61801, 1
Centre for Bacterial Cell Biology, Newcastle University, Framlington Place, Newcastle upon
Tyne NE2 4HH, United Kingdom, 2
Institute for Cell and Molecular Biosciences, Newcastle University, Framlington Place,
Newcastle upon Tyne NE2 4HH, United Kingdom 3
Flagellar assembly proceeds in a sequential manner, beginning at the base and
concluding with the filament. A critical aspect of assembly is that gene expression is coupled to
assembly. When cells transition from a nonflagellated to a flagellated state, gene expression is
sequential, reflecting the manner in which the flagellum is made. A key mechanism for
establishing this temporal hierarchy is the σ 28 -FlgM checkpoint, which couples the expression of
late flagellar (Pclass3) genes to the completion of the hook-basal body. In this work, we
investigated the role of FliZ in coupling middle flagellar (Pclass2) gene expression to assembly
in Salmonella enterica serovar Typhimurium (Salmonella). We also demonstrate that significant
cross talk exists between different secretion systems in Salmonella with FliZ as the cross talk
element. Specifically, we show that FliZ is also an activator of Salmonella Pathogenicity Island-1
(SPI1) encoded virulence genes and the fim, lpf, std, saf, bcf, stb, stc, stf, and sth loci encoded
fimbriae in Salmonella. We demonstrate that FliZ is an FlhD4C2-dependent activator of
Pclass2/middle gene expression. Our results suggest that FliZ regulates the concentration of
FlhD4C2 posttranslationally which leads to faster induction of Pclass2/middle genes. We also
demonstrate that FliZ functions independently of the flagellum-specific sigma factor σ 28 and the
filament-cap chaperone/ FlhD4C2 inhibitor FliT. We correlate our gene expression experiments
by discussing the role of FliZ in flagellar biosynthesis during swimming and swarming motility.
FliZ was found to effect SPI1 activity levels in a HilD dependent posttranslational manner and its
effect on type I fimbriae gene expression was found to be FimZ dependent.
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