Analysis of the Activity and Regulon of the Two-component Regulatory System Composed by Cjj1484 and Cjj1483 of Campylobacter jejuni

Campylobacter jejuni is a leading cause of bacterial diarrheal disease and a frequent commensal of the intestinal tract of 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 Cjj1484 histidine kinase and the 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 both in 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. Overall design: Three-condition experiment, WT C. jejuni 81-176 SmR (DRH212) and isogenic ΔCjj1484 (PML360) and ΔCjj1483 (PML335). Biological replicates: 3 81-176 SmR, 3 ΔCjj1484 (PML360), and 3 ΔCjj1483 (PML335)independently grown to log phase and harvested. Two technical replicates/biological replicate. One replicate per array. A type 2 gene expression experimental design was used, with fluorescently labeled genomic DNA as a reference channel in each experiment as described by Lucchini, S., et al. 2005. Infect Immun 73:88-102.