Differential effects of short-chain fatty acids and iron on expression of iha in Shiga-toxigenic Escherichia coli

• Published in: Microbiology (Society for General Microbiology) Vol. 155; no. 11; pp. 3554 - 3563
• Main Authors: Herold, Sylvia, Paton, James C, Srimanote, Potjanee, Paton, Adrienne W
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01.11.2009; Society for General Microbiology
• Subjects: Bacterial Adhesion; Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - metabolism; Bacteriology; Biological and medical sciences; Colon - microbiology; Culture Media; DNA, Bacterial - genetics; Escherichia coli; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Fatty Acids, Volatile - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Ileum - microbiology; Iron - metabolism; Microbiology; Mutagenesis; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Shiga-Toxigenic Escherichia coli - genetics; Shiga-Toxigenic Escherichia coli - metabolism; Short chain; Escherichia coli; Bacteria; Lipids; Iron; Fatty acids; Shiga like toxin; Enterobacteriaceae
• ISSN: 1350-0872; 1465-2080; 1465-2080
• DOI: 10.1099/mic.0.029454-0

Research Centre for Infectious Diseases, School of Molecular and Biomedical Science, University of Adelaide, South Australia, 5005, Australia Shiga-toxigenic Escherichia coli (STEC) colonizing the bowel are exposed to a variety of short-chain fatty acids (SCFAs), including acetate, propionate and butyrate, produced by gut microflora. However, the total concentrations and relative amounts of SCFAs in the lumen vary with intestinal niche. Here we report that conditions simulating SCFA concentrations present in the human gut trigger expression of the iha gene, which encodes an adherence-conferring outer-membrane protein of pathogenic E. coli . We show that growth under conditions simulating colonic, but not ileal, SCFA concentrations increases iha expression in three tested STEC strains, with the strongest expression detected in LEE-negative STEC O113:H21 strain 98NK2. Expression of iha is known to be subject to Fur-mediated iron repression in O157:H7 STEC, and the same occurs in 98NK2. However, exogenous iron did not repress iha expression in the presence of colonic SCFAs in either 98NK2 or the O157:H7 strain EDL933. Moreover, exposure to the iron chelator 2,2'-dipyridyl caused no further enhancement of iha expression over that induced by colonic SCFAs. These findings indicate that SCFAs regulate iha expression in STEC independently of iron. Increased expression of iha under colonic but not ileal SCFA conditions possibly may contribute to preferential colonization of the human colon by STEC. Correspondence Adrienne W. Paton adrienne.paton{at}adelaide.edu.au Abbreviations: LEE, locus of enterocyte effacement; HUS, haemolytic uraemic syndrome; SCFA, short-chain fatty acid; STEC, Shiga-toxigenic Escherichia coli ; UPEC, uropathogenic E. coli