Finding Regulators Associated with the Expression of the Long Polar Fimbriae in Enteropathogenic Escherichia coli.
Enteropathogenic Escherichia coli (EPEC) is a human pathogen that requires initial adhesion to the intestine in order to cause disease. Multiple adhesion factors have been identified in E. coli strains, among them the long polar fimbriae (Lpf), a colonization factor associated with intestinal adhesion. The conditions of Lpf expression are well understood in enterohemorrhagic E. coli (EHEC); however, the expression of EPEC lpf has been found to be repressed under any in vitro condition tested. Therefore, we decided to identify those factors silencing expression of EPEC lpf. Because histone-like nucleoid structuring protein (H-NS) is a known repressor of EHEC lpf, we tested it and found that H-NS is a repressor of EPEC lpf. We also found that the adhesion of the EPEC Δhns strain was significantly enhanced compared to the wild-type strain. Because lpf expression was modestly increased in the hns mutant, transposon mutagenesis was performed to find a strain displaying higher lpf expression than EPEC Δhns. One Tn5 insertion was identified within the yhjX gene, and further in vitro characterization revealed increased lpf expression and adhesion to Caco-2 cells compared with EPEC Δhns. However, in a murine model of intestinal infection, the EPEC Δhns and EPEC Δhns Tn5 mutants had only a slight change in colonization pattern compared to the wild-type strain. Our data showed that EPEC Lpf is transcribed, but its role in EPEC intestinal colonization requires further analysis.


OBJECTIVE
Data are presented demonstrating that the long polar fimbriae (lpf) operon in enteropathogenic E. coli (EPEC) is highly regulated; however, derepression occurs by mutagenizing two proteins associated with its control. The study demonstrates that the EPEC lpf operon can be expressed and, therefore, participates in the EPEC adherence phenotype.
Department of Microbiology and Immunology, Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, Texas, USA.
Jia
J
Hu
Department of Microbiology and Immunology, Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, Texas, USA.
Brittany N
BN
Ross
Department of Microbiology and Immunology, Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, Texas, USA.
Roberto J
RJ
Cieza
Department of Microbiology and Immunology, Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, Texas, USA Department of Pathology, Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, Texas, USA altorres@utmb.edu.
Alfredo G
AG
Torres
D000818:Animals; D001422:Bacterial Adhesion; D054308:Enteropathogenic Escherichia coli / Q000235:genetics / Q000378:metabolism*; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D036781:Fimbriae Proteins / Q000235:genetics* / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008813:Mice, Inbred ICR; D009876:Operon
D029968:Escherichia coli Proteins; C529458:FimG protein, E coli; C571199:LpfA1 protein, E coli; D026901:Membrane Transport Proteins; C579564:YhjX protein, E coli; D036781:Fimbriae Proteins