title: c-di-GMP signaling regulates E. coli O157:H7 adhesion to colonic epithelium.
abstract: Escherichia coli O157:H7 is an important foodborne pathogen that causes serious illness in humans at low infectious doses. The main source of infections is beef or greens contaminated with E. coli O157:H7 shed by cattle. Here we investigated the role of c-di-GMP-dependent signal transduction in cattle gut colonization of E. coli O157:H7. To manipulate intracellular c-di-GMP levels, we introduced into E. coli O157:H7 a c-di-GMP specific phosphodiesterase (PDE). Liquid chromatography tandem mass spectrometry analysis confirmed that in E. coli O157:H7, over-expression of PDE decreased c-di-GMP level. Consistent with the altered c-di-GMP level, PDE overexpression resulted in decreased biofilm formation in E. coli O157:H7. Furthermore, this diminished c-di-GMP levels reduced adhesion of E. coli O157:H7 to both cultured HT-29 cells and cattle colon explants. Consistently, mRNA levels of genes involved in adhesion were down-regulated including genes encoding E. coli common pili, long polar fimbriae 1, hemorrhagic coli pilus, as well as intimin and tir. We further observed decreased curli fimbriae synthesis in the strain with decreased c-di-GMP levels, which was supported by the reduction in the transcription of curli large subunit gene csgA and the curli expression regulator gene csgD. Genes for enterocyte effacement encoded regulator (Ler) and type III secretion system effectors, EspA and EspB, were also down-regulated. Collectively, data indicated that c-di-GMP signaling positively regulates E. coli O157:H7 intestinal epithelial cell and tissue colonization and expression of associated adhesion factors.
authors.affiliation: Department of Animal Science, University of Wyoming, Laramie, WY 82071, USA.
authors.forename: Jia
authors.initials: J
authors.lastname: Hu
authors.forename: Baolin
authors.initials: B
authors.lastname: Wang
authors.forename: Xin
authors.initials: X
authors.lastname: Fang
authors.forename: Warrie J
authors.initials: WJ
authors.lastname: Means
authors.forename: Richard J
authors.initials: RJ
authors.lastname: McCormick
authors.forename: Mark
authors.initials: M
authors.lastname: Gomelsky
authors.forename: Mei-Jun
authors.initials: MJ
authors.lastname: Zhu
mesh_terms: D000818:Animals; D002417:Cattle; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism; D020895:Enterocytes / Q000382:microbiology; D004847:Epithelial Cells / Q000382:microbiology*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000503:physiopathology; D019453:Escherichia coli O157 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D019073:HT29 Cells; D006801:Humans; D007422:Intestines / Q000382:microbiology*; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D029968:Escherichia coli Proteins; C062025:bis(3',5')-cyclic diguanylic acid; D006152:Cyclic GMP