Affiliation:
1. Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
Abstract
ABSTRACT
Activation of σ
54
-dependent gene expression essential for formation of flagella in
Campylobacter jejuni
requires the components of the inner membrane-localized flagellar export apparatus and the FlgSR two-component regulatory system. In this study, we characterized the FlgS sensor kinase and how activation of the protein is linked to the flagellar export apparatus. We found that FlgS is localized to the
C. jejuni
cytoplasm and that His141 of FlgS is essential for autophosphorylation, phosphorelay to the cognate FlgR response regulator, motility, and expression of σ
54
-dependent flagellar genes. Mutants with incomplete flagellar export apparatuses produced wild-type levels of FlgS and FlgR, but they were defective for signaling through the FlgSR system. By using genetic approaches, we found that FlgSR activity is linked to and downstream of the flagellar export apparatus in a regulatory cascade that terminates in expression of σ
54
-dependent flagellar genes. By analyzing defined
flhB
and
fliI
mutants of
C. jejuni
that form flagellar export apparatuses that are secretion incompetent, we determined that formation of the apparatus is required to contribute to the signal sensed by FlgS to terminate in activation of expression of σ
54
-dependent flagellar genes. Considering that the flagellar export apparatuses of
Escherichia coli
and
Salmonella
species influence σ
28
-dependent flagellar gene expression, our work expands the signaling activity of the apparatuses to include σ
54
-dependent pathways of
C. jejuni
and possibly other motile bacteria. This study indicates that these apparatuses have broader functions beyond flagellar protein secretion, including activation of essential two-component regulatory systems required for expression of σ
54
-dependent flagellar genes.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
62 articles.
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