Characterization of Campylobacter jejuni RacRS Reveals Roles in the Heat Shock Response, Motility, and Maintenance of Cell Length Homogeneity

Abstract

bCampylobacter jejuni commensally colonizes the cecum of birds. The RacR (reduced ability to colonize) response regulator was previously shown to be important in avian colonization. To explore the means by which RacR and its cognate sensor kinase RacS may modulate C. jejuni physiology and colonization, ⌬racR and ⌬racS mutations were constructed in the invasive, virulent strain 81-176, and extensive phenotypic analyses were undertaken. Both the ⌬racR and ⌬racS mutants exhibited a ϳ100-fold defect in chick colonization despite no (⌬racS) or minimal (⌬racR) growth defects at 42°C, the avian body temperature. Each mutant was defective for colony formation at 44°C and in the presence of 0.8% NaCl, both of which are stresses associated with the heat shock response. Promoter-reporter and real-time quantitative PCR (RT-qPCR) analyses revealed that RacR activates racRS and represses dnaJ. Although disregulation of several other heat shock genes was not observed at 38°C, the ⌬racR and ⌬racS mutants exhibited diminished upregulation of these genes upon a rapid temperature upshift. Furthermore, the ⌬racR and ⌬racS mutants displayed increased length heterogeneity during exponential growth, with a high proportion of filamented bacteria. Filamented bacteria had reduced swimming speed and were defective for invasion of Caco-2 epithelial cells. Soft-agar studies also revealed that the loss of racR or racS resulted in whole-population motility defects in viscous medium. These findings reveal new roles for RacRS in C. jejuni physiology, each of which is likely important during colonization of the avian host.

The Campylobacter jejuni RacRS system regulates fumarate utilization in a low oxygen environment

“…Previous studies have demonstrated that the RacRS two-component system is important for C. jejuni to colonize chickens and that this system supports growth at 42°C (Bras et al, 1999) or above 42°C (Apel et al, 2012). Two genes, encoding a periplasmic cytochrome c peroxidase homologue Cj0358 (Bras et al, 1999) and dnaJ encoding a heat shock chaperone (Apel et al, 2012), have been reported to be regulated by RacR.…”

“…So far two genes are known to be regulated by RacR, i.e. a periplasmic cytochrome c peroxidase homologue Cj0358 (Bras et al, 1999) and dnaJ encoding a heat shock chaperone (Apel et al, 2012).…”

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

“…Whereas DccRS directly influences expression of genes encoding colonization determinants (22), CprRS is required for expression of genes for biofilm formation (24). RacRS is required for expression of genes encoding proteins for the heat shock response and fumarate metabolism, depending on the strain and growth conditions used for analysis (25)(26)(27). Additionally, the PhosSR TCS is required for expression of 12 genes, 5 of which encode proteins required for phosphate acquisition (28).…”

“…For instance, the FlgSR TCS monitors formation of the flagellar type III secretion system, the MS ring, and rotor structures to activate expression of 54 -dependent flagellar genes required for motility and commensal colonization (15)(16)(17)(18)(19)(20)(21). Furthermore, DccRS, CprRS, and RacRS are required for wild-type (WT) levels of commensal colonization of the chick ceca (22)(23)(24)(25)(26). Whereas DccRS directly influences expression of genes encoding colonization determinants (22), CprRS is required for expression of genes for biofilm formation (24).…”

Narrow-spectrum inhibitors targeting an alternative menaquinone biosynthetic pathway of Helicobacter pylori

“…4). Thus, 5'-methylthioadenosine nucleosidase was found to play a key role in the futalosine pathway of H. pylori (i.e., chorismate / 6-amino-6-deoxyfutalosine / dehypoxanthinyl futalosine / cyclic dehypoxantine futalosine / 1,4-dihydroxy-6-naphthoic acid / MK) [29,30]. FAs have been shown to possibly inhibit a step after the formation of futalosine [24].…”