PhD thesis of Clémence Bièche (2007-2010)

Nowadays Campylobacter jejuni is the leading cause of bacterial foodborne infections worldwide. Studies on C. jejuni susceptibility to environmental stresses showed an easy control of this microorganism. Moreover the NCTC 11168 strain DNA sequencing highlighted the absence of several genes encoding for classical enterobacteria resistance mechanisms. However this pathogen succeed to reach consumers. C. jejuni must have unidentified cellular mechanisms to respond to stresses. High pressure is an innovating stabilizing food process. This non thermal technology allows to preserve some fresh product qualities. Its action on material is mechanical: it causes molecular weak linkage by reducing volume. Its bactericidal power has been proved with many non sporulated bacteria. In this study, we observe high pressure effects on C. jejuni. This thesis presents a comparison of two C. jejuni strains, NCTC 11168 and 81-176, treated by high pressure with different parameters (pressure intensity, treatment temperature, pH). In order to explain observed differences, membrane fatty acid profiles and fluidities have been compared on both strains. In another hand, a proteomic study using two-dimensional electrophoresis with the C. jejuni 81-176 strain is related: evolution of cytosolic proteome during recovery after a non bactericidal treatment, effect of high pressure on membrane sub-proteomes, and a study of membre complexome by BN-SDS-PAGE.