Project description:Campylobacter jejuni is the major cause of acute gastroenteritis in the developed world. It is usually acquired through contaminated poultry as C. jejuni causes a silent asymptomatic infection of the chicken. Pathogens face different sources of stress during its transit through the gut. In this study, we describe the ability of C. jejuni to survive nitrosative stress at very low oxygen levels that reflect those in hypoxic gut environments. Specifically, we here explore an innovative model of signal recognition during colonization. We use a diffusion capsule to feed small, diffusible molecules from chicken caecal matter into a microaerobic C. jejuni culture to study the transcriptomic changes mounted as response to chemical signals present in the chicken gut. We find that in early stages of exposure to the caecal contents (10 min) the dual component colonization regulator, dccR, plays an important yet not fully understood role. Although the caecal material contains cyanide derived from plant sources, we find no role for a truncated globin (encoded by ctb), which has previously been implicated in resistance to this haem ligand.
Project description:The human intestinal microbiota associated with rats produces in vivo a soluble(s) factor(s) that down-regulates the expression of genes encoding for the Shiga toxin II in E. coli O157:H7. The Shiga toxin II is one of the major virulence factors of E. coli enterohemorragic leading to the deadly hemolitic and uremic syndrome. Investigation of the effect of the human intestinal microbiota on the whole transcriptome of EHEC O157:H7 is of major importance to increase our understanding of the pathogen transcriptomic adaptation in response to the human microbiota. We analysed by microarray hybridization the gene expression pattern of EHEC O157:H7 grown in the caecal content of germ-free rats or rats associated with the human microbiota of a healthy human subject. By doing so, we increased our understanding of the regulatory activities of the human gut microbiota on E. coli O157:H7 A first group of twelve weeks old, male, germfree rats was colonized with the human fecal microbiota and a second group was kept germfree and condidered as a controle group. Rats were fed for two weeks with a sterile human type diet, and were sacrificed. E. coli O157:H7 was cultivated for 6 hours in the caecal content of germfree rats and rats associated with the human intestinal microbiota. RNAs were extracted and cDNAs were synthesized, fragmented and biotinylated before being hybridized on Affymetrix E. coli genome 2.0 arrays. The effect of the human intestinal microbiota was investigated by comparing the gene expression level in the caecal content of rats associated with the human microbiota with their expression level in the caecal content of the germfree rats.
