Bile salts induce expression of the afimbrial LDA adhesin of atypical enteropathogenic Escherichia coli

Alfredo Torres, Christopher B. Tutt, Lisabeth Duval, Vsevolod Popov, Abdelhakim Ben Nasr, Jane Michalski, Isabel C A Scaletsky

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Atypical enteropathogenic Escherichia coli (aEPEC) strains are frequently implicated in infant diarrhoea in developing countries. Not much is known about the adherence properties of aEPEC; however, it has been shown that these strains can adhere to tissue-cultured cells. A chromosomal region designated the locus for diffuse adherence (LDA) confers aEPEC strain 22 the ability to adhere to culture cells. LDA is an afimbrial adhesin that contains a major subunit, LdaG, whose expression is induced on MacConkey agar at 37°C. We hypothesized that the bile salts found in this culture media induce the expression of LdaG. Strain 22 and the LdaG mutant were grown in Luria-Bertani (LB) media in the presence or absence of bile salts and heat-extracted surface-expressed proteins were separated by SDS-PAGE to determine whether expression of the 25kDa LdaG protein was induced. Western blot analysis with anti-LdaG confirmed that bile salts enhance LdaG expression at 37°C. Adhesion assays on HeLa cells revealed that adhesion in a diffuse pattern of strain 22 increased in the presence of bile salts. We also confirmed that expression of the localized adherence pattern observed in the ldaG mutant required the presence of a large cryptic plasmid found in strain 22 and that this phenotype was not induced by bile salts. At the transcriptional level, the ldaG-lacZ promoter fusion displayed maximum beta-galactosidase activity when the parent strain was grown in LB supplemented with bile salts. Fluorescence Activated Cell Sorting analysis, immunogold labelling electron microscopy and immunofluorescence using anti-LdaG sera confirmed that LDA is a bile salts-inducible surface-expressed afimbrial adhesin. Finally, LdaG expression was induced in presence of individual bile salts but not by other detergents. We concluded that bile salts increase expression of LDA, conferring a diffuse adherence pattern and having an impact on the adhesion properties of this aEPEC strain.

Original languageEnglish (US)
Pages (from-to)1039-1049
Number of pages11
JournalCellular Microbiology
Volume9
Issue number4
DOIs
StatePublished - Apr 2007

Fingerprint

Enteropathogenic Escherichia coli
Bile Acids and Salts
Escherichia coli
Adhesion
Cells
beta-Galactosidase
HeLa Cells
Sorting
Cell culture
Developing countries
Cell Adhesion
Detergents
Labeling
Electron microscopy
Developing Countries
Agar
Fluorescent Antibody Technique
Culture Media
Polyacrylamide Gel Electrophoresis
Cultured Cells

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Microbiology

Cite this

Bile salts induce expression of the afimbrial LDA adhesin of atypical enteropathogenic Escherichia coli. / Torres, Alfredo; Tutt, Christopher B.; Duval, Lisabeth; Popov, Vsevolod; Nasr, Abdelhakim Ben; Michalski, Jane; Scaletsky, Isabel C A.

In: Cellular Microbiology, Vol. 9, No. 4, 04.2007, p. 1039-1049.

Research output: Contribution to journalArticle

Torres, Alfredo ; Tutt, Christopher B. ; Duval, Lisabeth ; Popov, Vsevolod ; Nasr, Abdelhakim Ben ; Michalski, Jane ; Scaletsky, Isabel C A. / Bile salts induce expression of the afimbrial LDA adhesin of atypical enteropathogenic Escherichia coli. In: Cellular Microbiology. 2007 ; Vol. 9, No. 4. pp. 1039-1049.
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AU - Nasr, Abdelhakim Ben

AU - Michalski, Jane

AU - Scaletsky, Isabel C A

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