Growth-phase-dependent expression of the operon coding for the glycosylated autotransporter adhesin AIDA-I of pathogenic Escherichia coli.

Abstract

The adhesin involved in diffuse adherence (AIDA-I) is an autotransporter found in pathogenic strains of Escherichia coli causing diarrhea in humans and pigs. The AIDA-I protein is glycosylated by a specific enzyme, the AIDA-associated heptosyltransferase (Aah). The aah gene is immediately upstream of the aidA gene, suggesting that they form an operon. However, the mechanisms of regulation of the aah and aidA genes are unknown. Using a clinical E. coli isolate expressing AIDA-I, we identified two putative promoters 149 and 128 nucleotides upstream of aah. Using qRT-PCR, we observed that aah and aidA are transcribed in a growth-dependent fashion, mainly at the start of the stationary phase. Western blotting confirmed that protein expression follows the same pattern. Using a fusion to a reporter gene, we observed that the regulation of the isolated aah promoter matched this transcription and expression pattern. Lastly, we found glucose to be a repressor and nutrient starvation to be an inducer. Taken together, our results suggest that, in the strain and the conditions we studied, aah-aidA is transcribed as a bicistronic message from a promoter upstream of aah, with maximal expression under conditions of nutrient limitation such as high cell density.

• Authors: Frédéric Berthiaume, Marie-Florence Leblond, Josée Harel, Michael Mourez
• Journal: FEMS microbiology letters (FEMS Microbiol Lett) Vol. 311 Issue 2 Pg. 176-84 (Oct 2010) ISSN: 1574-6968 [Electronic] England
• PMID: 20831592 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2010 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Chemical References

• AIDA-I protein, E coli
• Adhesins, Escherichia coli
• Escherichia coli Proteins
• Glycosyltransferases
• autotransporter-adhesin-heptosyltransferase, E coli

Topics

• Adhesins, Escherichia coli (genetics, metabolism)
• Base Sequence
• Escherichia coli (genetics, growth & development, metabolism, pathogenicity)
• Escherichia coli Infections (microbiology)
• Escherichia coli Proteins (genetics, metabolism)
• Gene Expression Regulation, Bacterial
• Glycosylation
• Glycosyltransferases (genetics, metabolism)
• Humans
• Molecular Sequence Data
• Operon
• Promoter Regions, Genetic