Effects Of CO₂ On Adherence Ability Of Enterohemorrhagic Escherichia Coli O157:H7

Enterohemorrhagic Escherichia coli O157:H7 is the most common member of pathogenic Escherichia coli strains, which can cause acute gastroenteritis, bloody diarrhea and haemorrhagic colitis. O157:H7 can adhere to epithelial cells and produce attaching / effacing lesions. The ability of the bacteria to adhere to the intestinal epithelial surface is thought to be vital and can reflect O157: H7 pathogenic capabilities. Most of virulence factors required to produce adherence are thought to be encoded by the locus for enterocyte effacement. These virulence factors are expressed only when required in response to environmental regulatory signals such as medium, temperature and pH. O157:H7 pathogenic mechanism has not been completely clarified. To explore CO₂ affecting adherence ability and virulence factors expression and further find some proteins involved in adherence, we did the following research.By O157:H7 infecting HeLa cells in vitro, we compared adherence ability of O157:H7 grown in DMEM in air with the ability of O157:H7 grown in DMEM in 5%CO₂, the results showed that O157:H7 grown in DMEM without shaking in 5%CO₂ adhered more efficiently to HeLa cells than O157:H7 grown in DMEM with 200rpm shaking in air. Then by Real-time PCR, we compared gene expression level of two virulence factors EspA and Tir in O157:H7 grown in these two kinds of condition, the results showed that transcription level of EspA and Tir were raised in O157:H7 grown in DMEM without shaking in 5%CO₂. Finally, through two-dimensional electrophoresis, we identified differentially expressed proteins in O157:H7 grown in these two kinds of condition, the results showed that there were 16 proteins expression changed, of which expression of 11 proteins were up-regulated while expression of 6 proteins were down-regulated.In summary, we proved CO₂ can indeed enhance the pathogenicity of O157:H7. Aslo we found some proteins which may be involved to adherence. Our research provides a new clue for founding some new proteins related to adherence formation and thoroughly explaining pathogenic molecular mechanism of O157: H7.