Acid and bile-salt stress of enteropathogenic Escherichia coli enhances adhesion to epithelial cells and alters glycolipid receptor binding specificity.
BACKGROUND
Enteropathogenic Escherichia coli (EPEC), a diarrheagenic pathogen, is exposed to stress during ingestion, and yet little is known about the impact of stress on EPEC-host cell adhesion.


METHODS
EPEC adhesion to human epithelial cells was assessed by plate-count assay before and after bacterial stress. Stress treatments included exposure to low pH (with or without acid adaptation) and exposure to physiological concentrations of 4 intestinal bile salts. Expression of bacterial adhesins after stress was assessed by immunoblot and flow-cytometric analysis. Bacteria-lipid binding was determined by thin-layer chromatography overlay assay.


RESULTS
Brief low-pH stress (with or without acid adaptation) and bile-salt stress resulted in significantly increased EPEC-host cell adhesion. Erythromycin pretreatment eliminated the adhesion enhancement, suggesting that protein synthesis was required. Immunoblot and flow-cytometric analysis indicated little change in expression of known adhesins after either stress. However, we found increased surface expression of a heat-shock protein 70 (Hsp70) on acid-shocked EPEC, and pretreatment with anti-Hsp70 eliminated the adhesion enhancement after acid stress. Acid shock also correlated with increased binding to sulfogalactosylceramide, a putative receptor for other pathogens after stress.


CONCLUSIONS
Acid/bile-salt stress of EPEC significantly enhances adhesion to host cells, and a novel adhesin-receptor pair may play a role in the adhesion.
de Jesus
Margaret C
MC
Department of Chemistry and Biology, Ryerson University, Toronto, Canada.
Urban
Agnieszka A
AA
Marasigan
Marastella E
ME
Barnett Foster
Debora E
DE
D000143:Acids / Q000494:pharmacology*; D018830:Adhesins, Escherichia coli / Q000378:metabolism; D001422:Bacterial Adhesion / Q000187:drug effects* / Q000502:physiology; D001647:Bile Acids and Salts / Q000494:pharmacology*; D018929:Cell Culture Techniques; D004847:Epithelial Cells / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects* / Q000378:metabolism / Q000472:pathogenicity; D018840:HSP70 Heat-Shock Proteins; D006801:Humans; D007413:Intestinal Mucosa / Q000276:immunology / Q000382:microbiology*; D011956:Receptors, Cell Surface / Q000378:metabolism*
D000143:Acids; D018830:Adhesins, Escherichia coli; D001647:Bile Acids and Salts; D018840:HSP70 Heat-Shock Proteins; D011956:Receptors, Cell Surface; C033639:glycolipid receptor