Campylobacter jejuni is the primary food borne bacterial pathogen in the developed world and the bacteria causes millions of gastroenteritis cases each year. The most important reservoir for C. jejuni is the gut of chickens, which are colonized commensally and efficiently by this organism. Predominantly the mucus filled crypts of the lower gastrointestinal tract of chickens are found to be colonized by C. jejuni, and the bacteria are expected to be attracted to this particular environment by chemotaxis. From the full genome sequence of C. jejuni NCTC11168 several chemotactic proteins and chemoreceptors have been predicted. In order to explore the role of chemotaxis in C. jejuni colonization we have constructed defined deletion mutants in the putative chemoreceptors. These mutants are analyzed for their motile characteristics and their chemotatic capacity in order to investigate the chemoreceptor function and to identify matching chemoeffectors. Furthermore, selected mutants will be investigated for their ability to colonize chickens with focus on establishment, level, and persistence. Special emphasis will be held at characterizing the colonization of mucus layers.