PhD thesis of Vicky Bronnec

Abstract of the thesis:

Campylobacter jejuni is leading cause of bacterial foodborne infections in the world. This pathogen is able to survive in various environments. From the digestive tract of poultry, its natural reservoir, to the consumer's plate, C. jejuni must develop several mechanisms to survive in hostile environments. Biofilm formation is an adaptive strategy to survive in these environments and under aerobic conditions. A clinical strain (C. jejuni Bf), isolated in our laboratory, has the unique feature in the species to grow aerobically. It has been used as a model to better describe the mechanisms of stress resistance in C. jejuni.
C. jejuni Bf has a high capacity to adhere to biotic and abiotic surfaces. This strain is able to develop a biofilm in both aerobic and microaerobic conditions and the CosR regulator implicated in oxidative stress response is overexpressed in aerobiosis. Its ability to develop a biofilm seems constitutive independently on aeration conditions, unlike other strains. The sequence of its genome does not reveal unique gene. However, some features seem to be shared only with few other strains, especially C. jejuni ATCC 33560 a non-aerotolerant strain. Within the remarkable differences in the genome of C. jejuni Bf, we noticed the presence of a type VI secretion system, a mutation point in the oorD gene, an insertion upstream dnaK gene. This suggests that the phenotype of C. jejuni Bf could only result from some changes and different regulation by CosR.

Keywords: Foodborne pathogen, oxidative stress, adhesion, biofilm, confocal microscopy, comparative ge-nomics.