The FlgS/FlgR Two-component Signal Transduction System Regulates the fla Regulon in Campylobacter jejuni

Abstract

The human pathogen Campylobacter jejuni is a highly motile organism that carries a flagellum on each pole. The flagellar motility is regarded as an important trait in C. jejuni colonization of the intestinal tract, however, the knowledge of the regulation of this important colonization factor is rudimentary. We demonstrate by phosphorylation assays that the sensor FlgS and the response regulator FlgR form a two-component system that is on the top of the Campylobacter flagellum hierarchy. Phosphorylated FlgR is needed to activate RpoNdependent genes of which the products form the hookbasal body filament complex. By real-time reverse transcriptase-PCR we identified that FlgS, FlgR, RpoN, and FliA belong to the early flagellar genes and are regulated by 70 . FliD and the putative anti--factor FlgM are regulated by a 54 -and 28 -dependent promoters. Activation of the fla regulon is growth phase-dependent, a 100-fold rpoN mRNA reduction is seen in the early stationary phase compared with the early logarithmic phase. Whereas flaB transcription decreases, flaA transcription increases in early stationary phase. Our data show that the C. jejuni flagellar hierarchy largely differs from that of other bacteria. Phenotypical analysis revealed that unflagellated C. jejuni mutants grow three times faster in broth medium compared with wild-type bacteria. In vivo the C. jejuni flagella are needed to pass the gastrointestinal tract of chickens, but not to colonize the ceaca of the chicken.

Deletion of a previously uncharacterized flagellar-hook-length control gene fliK modulates the σ 54-dependent regulon in Campylobacter jejuni

“…Hendrixson & DiRita (2003) also confirmed the predicted identity of Cj0793 (named flgS) as the gene encoding the cognate sensor for FlgR (Jagannathan et al, 2001), forming a two-component sensor-regulator system controlling s 54 . Wosten et al (2004) have confirmed that a phospho-transfer relay mediates this two-component regulation. Using microarrays and proteomic analyses to investigate variants of strain NCTC 11168, Carrillo et al (2004) have demonstrated the importance of genes with predicted promoters dependent on s 54 and s 28 in motility-associated attenuation of a poorly motile stock strain, identified middle and late genes involved in the flagellar gene expression cascade, and demonstrated key roles for flhA and fliA.…”

“…The observation that transcription of fliA, encoding s 28 and other genes in the Cj0062c-fliY gene cluster, appears from the fliK mutant experiment to be s 54 -dependent is novel; these genes were earlier predicted to be transcribed from a s 70 -dependent promoter (Carrillo et al, 2004;Wosten et al, 2004). Transcription is presumably initiated from the apparent s 54 -dependent canonical promoter element located upstream of Cj0062c and within the coding sequence of Cj0063c (flhG) ( Table 3).…”

“…We and others have since confirmed the involvement of s 54 in flagellar biogenesis, and its regulation by an NtrC family regulator FlgR (Carrillo et al, 2004;Hendrixson & DiRita, 2003;Jagannathan et al, 2001;Wosten et al, 2004). However, several flagellar genes known from the enteric model, including the regulatory gene fliK that encodes a hook-length control and export specificity switch, have not been identified from the genome sequence (Parkhill et al, 2000).…”

CmeR Functions as a Pleiotropic Regulator and Is Required for Optimal Colonization of Campylobacter jejuni In Vivo

“…CbrR modulates the Campylobacter response to bile, but its cognate sensor kinase and the target genes controlled by it are unknown (36). The FlgSR system controls the flagellar regulon and affects the motility of Campylobacter (50). It was also found that FlaR undergoes phase variation due to the presence of homopolymeric tracts of adenine and thymine in the coding gene (13).…”

“…In C. jejuni NCTC 11168 and RM1221, each system has nine response regulators and six histidine sensor kinases (9,32). Several of the regulators or TCR systems, including DccRS (28), PhosSR (49), FlgSR (50), CbrR (36), RacRS (4), and CheY (53), have been studied, and all were found to be required for Campylobacter colonization in vivo. The RacRS system is responsive to temperature and controls the expression of multiple proteins in C. jejuni, while the PhosSR system senses phosphate conditions and modulates the expression of 12 genes that are involved in phosphate transport and utilization (4,49).…”