A novel Campylobacter jejuni two-component regulatory system important for temperature-dependent growth and colonization

Abstract

Campylobacter jejuni colonizes the intestines of domestic and wild animals and is a common cause of human diarrheal disease. We identified a two-component regulatory system, designated the RacR-RacS (reduced ability to colonize) system, that is involved in a temperature-dependent signalling pathway. A mutation of the response regulator gene racR reduced the organism's ability to colonize the chicken intestinal tract and resulted in temperature-dependent changes in its protein profile and growth characteristics.

FIG. 1

Growth patterns of the parent and mutant strains. The growth profiles of 81116, AB1, and AB2 were analyzed when the strains were incubated in MH broth at 37 and 42°C. Each point represents the mean (± standard deviation) of two cultures. ●, 81116; ⧫, AB1; ■, AB2. O.D., optical density.

FIG. 2

Colonization of 1-day-old chicks with C. jejuni. Shown is a comparison of the abilities of 81116 and AB1 to colonize the intestines of 1-day-old chicks. The threshold of detection in this model is 100 CFU/g of cecal contents (c.c.). (A) Number of viable bacteria recovered from the cecal contents of chicks. Each point on the graph is the mean for 10 chicks. The data for the mutant strains was derived from three separate experiments. ■, 81116; ○, AB1 (experiment 1); ▵, AB1 (experiment 2); ◊, AB1 (experiment 3). (B) Frequency of chick colonization. Black bars, 81116; gray bars, AB1 (experiments 1 to 3). The asterisk signifies no colonization with AB1.