Analysis of the Activity and Regulon of the Two-Component Regulatory System Composed by Cjj81176_1484 and Cjj81176_1483 of Campylobacter jejuni

Abstract

Campylobacter jejuni is a leading cause of bacterial diarrheal disease and a frequent commensal of the intestinal tract in poultry and other animals. For optimal growth and colonization of hosts, C. jejuni employs two-component regulatory systems (TCSs) to monitor environmental conditions and promote proper expression of specific genes. We analyzed the potential of C. jejuni Cjj81176_1484 (Cjj1484) and Cjj81176_1483 (Cjj1483) to encode proteins of a cognate TCS that influences expression of genes possibly important for C. jejuni growth and colonization. Transcriptome analysis revealed that the regulons of the Cjj81176_1484 (Cjj1484) histidine kinase and the Cjj81176_1483 (Cjj1483) response regulator contain many common genes, suggesting that these proteins likely form a cognate TCS. We found that this TCS generally functions to repress expression of specific proteins with roles in metabolism, iron/heme acquisition, and respiration. Furthermore, the TCS repressed expression of Cjj81176_0438 and Cjj81176_0439, which had previously been found to encode a gluconate dehydrogenase complex required for commensal colonization of the chick intestinal tract. However, the TCS and other specific genes whose expression is repressed by the TCS were not required for colonization of chicks. We observed that the Cjj1483 response regulator binds target promoters in both unphosphorylated and phosphorylated forms and influences expression of some specific genes independently of the Cjj1484 histidine kinase. This work further expands the signaling mechanisms of C. jejuni and provides additional insights regarding the complex and multifactorial regulation of many genes involved in basic metabolism, respiration, and nutrient acquisition that the bacterium requires for optimal growth in different environments. IMPORTANCEBacterial two-component regulatory systems (TCSs) link environmental cues to expression of specific genes that enable optimal bacterial growth or colonization of hosts. We found that the Campylobacter jejuni Cjj1484 histidine kinase and Cjj1483 response regulator function as a cognate TCS to largely repress expression of target genes encoding a gluconate dehydrogenase complex required for commensal colonization of the chick intestinal tract, as well as other genes encoding proteins for heme or iron acquisition, metabolism, and respiration. We also discovered different modes by which Cjj1483 may mediate repression with and without Cjj1484. This work provides insight into the signal transduction mechanisms of a leading cause of bacterial diarrheal disease and emphasizes the multifactorial and complex regulation of specific biological processes in C. jejuni.

Transcriptome and proteome dynamics in chemostat culture reveal how Campylobacter jejuni modulates metabolism, stress responses and virulence factors upon changes in oxygen availability

“…We showed by modelling that RacR activity decreases during the high to low oxygen shift and this can account for changes in expression of its major target genes, i.e., mfr, aspA, dcuA, cj0358 seen in this study. The signal for the Cj1491/Cj1492 system is unknown but this system seems mainly to regulate the gluconate dehydrogenase (cj0414/ 415) and possibly the c-type cytochrome cj0037c (cccC) genes (Luethy et al, 2015), both of which we identified as oxygen-regulated in this study. The Cj1492 response regulator was also approximately twofold higher in abundance at 40% versus 150% aerobiosis (Supporting Information Table S2).…”

“…At least three regulatory systems are, however, known to affect expression of different electron transport genes in C. jejuni. These are the RacRS two-component system (van der Stel et al, 2015), the Cj1491/Cj1492 twocomponent system (Luethy et al, 2015) and the LysR family regulator Cj1000 (Dufour et al, 2013). Of these, RacRS is understood in most detail and responds to low oxygen in the presence of nitrate or TMAO to effectively repress fumarate transport and respiration genes (van der Stel et al, 2015).…”

A PAS domain-containing regulator controls flagella-flagella interactions in Campylobacter jejuni

“…Of these, the CetB and CetC proteins, consisting of single PAS domains, and CetZ, consisting of two tandem PAS domains linked to a methyl-accepting chemotaxis domain are involved in energy and redox taxis (Hendrixson et al, 2001 ; Reuter and van Vliet, 2013 ). The Cj1491-92c two-component system has a PAS domain-containing histidine kinase, and controls expression of a gluconate dehydrogenase, and other proteins involved in heme or iron acquisition, and respiration (Luethy et al, 2015 ). Based on the Pfam classification of domains, all these PAS domains fall into the PAS9 family.…”

“…The Campylobacter genome encodes other environmental sensing modules, including those involved in chemotactic sensing (Marchant et al, 2002 ) and gene regulation (Raphael et al, 2005 ). Among the repertoire of sensing modules, PAS domains have been linked to both chemotaxis sensors (Reuter and van Vliet, 2013 ) and two-component sensors (Luethy et al, 2015 ). PAS (Per, Arnt, Sim) domains are wide-spread in bacteria, archea, and eukaryotes, and have roles in sensing a wide range of stimuli including light, oxygen, redox potential, and even play a role in circadian regulation in higher eukaryotes (Taylor and Zhulin, 1999 ).…”

Campylobacter jejuni transcriptional and genetic adaptation during human infection

“…Table 6 ). CJJ81176_1483 is part of a newly identified two-component system that regulates a gluconate dehydrogenase complex important for chick colonization 31 . These data represent 3 distinct genetic variations (PV, SNP, and MNV) in genes with diverse roles (chicken colonization, osmotic stress/house keeping, two-component system) and demonstrate the genetic adaptability of C. jejuni in vivo .…”