Speaker: Alain Stintzi Unraveling the secret life of Campylobacter jejuni Microbial factors governing the infection process of C. jejuni are poorly characterized. Undoubtedly, the pathogenesis of C. jejuni infection depends on its ability to adapt to the harsh environmental conditions encountered during transmission and colonization of its host. In particular, it will be unavoidably exposed to temperature shifts, iron restriction, acidic shock and oxidative stresses during the course of its contamination and infection cycle. Undeniably, survival in such hostile environments depends on efficient defense mechanisms. To characterize these mechanisms, a 2 steps approach was used. First, the transcriptional response of C. jejuni to these various environmental stresses was investigated in vitro using genome-wide technologies. Second, three animal models were implemented to characterize the transcriptome profile of C. jejuni while colonizing the gastrointestinal tract, transiting through the stomach, and interacting with the host neutrophiles. The integration of the in vitro and in vivo transcriptional profiles of C. jejuni revealed possible mechanisms by which C. jejuni colonizes and adapts to the host. Finally, several of the key genes were mutated to further study their biochemical function and their role in gut colonization and pathogenesis. Overall, this study identified novel colonization factors and thus contributes to a better understanding of Campylobacter pathogenesis.