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Growth phase-dependent activation of the DccRS regulon of Campylobacter jejuni

ABSTRACT: Two-component systems are widespread prokaryotic signal transduction devices which allow the regulation of cellular functions in response to changing environmental conditions. The two-component system DccRS (Cj1223-Cj1222) of Campylobacter jejuni is important for the colonization of chickens. Here we dissected the DccRS system in more detail and provide evidence that the sensor DccS selectively phosphorylates the cognate effector DccR. Microarray expression profiling, real-time RT-PCR, EMSA, and primer extension analyses revealed that the DccRS regulon of strain 81116 consists of five promoter elements all containing the consensus direct repeat sequence WTTCAC-N6-TTCACW covering the putative -35 promoter regions. One of these promoters is located in front of an operon encoding a putative macrolide efflux pump while the others are in front of genes coding for putative periplasmic or membrane proteins. The DccRS regulated genes in C. jejuni strain 81116 are needed to enhance early in vivo growth of C. jejuni in 7-day old chicken. The DccRS system is activated in the late stationary bacterial growth phase, probably via the release of metabolic products. Whole genome mRNA profiling and real-time RT-PCR analysis under these conditions demonstrated that the system has no influence on the transcription of genes outside the DccRS regulon.

ORGANISM(S): Campylobacter jejuni subsp. jejuni 81116 Campylobacter jejuni

PROVIDER: GSE19803 | GEO | 2010/01/09

SECONDARY ACCESSION(S): PRJNA121835

REPOSITORIES: GEO

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Project description:Campylobacter, a major foodborne pathogen, is increasingly resistant to macrolide antibibotics. Previous findings suggeted that development of macrolide resistance in campylobacter requires a multi-step process, but the molecular mechanisms involved in the process are not known. In our study, multiple series of macrolide-resistant C. jejuni mutants were selected in vitro by stepwise exposure of C. jejuni NCTC11168 to increasing concentrations of erythromycin and tylosin. A set of the selected resistance were subjected to microarray and the the global transcriptional profile was analyzed. In this sery, DNA microarray was used to compare the gene expression profiles of macrolide resistant strains (68E1, 68E8 and 68E64) with its parent wild-type strain NCTC11168. The assay identified a small number of genes that showed significant changes (q-value<0.1) in expression in the low-level macrolide resistant strain 68E1, while a large number of gene showing significant changes in intermedia-level resistant stran 68E8 and high-level resistant strain 68 E64. The up-regulated genes in the resistant strains are involved in miscellaneous periplasmic proteins, efflux protienand putative aminotransferase, while the majority of the down-regulated genes are involved in electron transport,lipoprotein, heat shock protein and unknown function proteins. These findings suggest that there is not much change in low-level macrolide resistant C. jejuni strain. The over-expression of efflux pump and periplasmic protein was involved in the development of resistance to macrolide in C. jejuni. Keywords: macrolide resistant C. jejuni selected from NCTC 11168 step-wise selection. The design utilized an available two color microarray slide for the entire transcriptome of Campylobacter jejuni. Four hybridizations were performed each with independently extracted samples of either macrolide susceptible C. jejuni NCTC11168 cDNA samples or macrolide resistant C.jejuni cDNA samples. A dye swap was utilized to help minimize dye dependent bias. Thus, there were four biological replicates of each sample.

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Growth phase-dependent activation of the DccRS regulon of Campylobacter jejuni

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