Bile salts affect expression of Escherichia coli O157:H7 genes for virulence and iron acquisition, and promote growth under iron limiting conditions

• Published in: PloS one 2013-09, Vol.8 (9), p.e74647
• Main Authors: Hamner, Steve, McInnerney, Kate, Williamson, Kerry, Franklin, Michael J, Ford, Timothy E
• Format: Article
• Language: English
• Subjects: Antimicrobial agents; Bacteria; Bacterial Adhesion - drug effects; Bacterial Adhesion - genetics; Bile; Bile Acids and Salts - pharmacology; Bile salts; Cell Membrane Permeability - drug effects; Cell membranes; Chelation; Chemotaxis; Chemotaxis - drug effects; Complications; Deoxyribonucleic acid; Detergents; Diarrhea; DNA; DNA damage; Down-Regulation - drug effects; Down-Regulation - genetics; E coli; Environmental changes; Escherichia coli; Escherichia coli O157 - drug effects; Escherichia coli O157 - genetics; Escherichia coli O157 - growth & development; Escherichia coli O157 - pathogenicity; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Flagella; Flagella - drug effects; Flagella - genetics; Gene expression; Gene Expression Regulation, Bacterial - drug effects; Genes; Genes, Bacterial - genetics; Genetic aspects; Genomic Islands - genetics; Genomics; Growth; Inflammatory bowel disease; Iron; Iron - metabolism; Iron - pharmacology; Membranes; Metabolism; Microbial drug resistance; Oligonucleotide Array Sequence Analysis; Pathogenicity; Pathogens; Permeability; Phosphoproteins - genetics; Phosphoproteins - metabolism; Physiological aspects; Proteins; RNA, Messenger - genetics; RNA, Messenger - metabolism; Salts; Small intestine; Studies; Transcription, Genetic - drug effects; Up-Regulation - drug effects; Up-Regulation - genetics; Virulence; Virulence - drug effects; Virulence - genetics
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0074647

Bile salts exhibit potent antibacterial properties, acting as detergents to disrupt cell membranes and as DNA-damaging agents. Although bacteria inhabiting the intestinal tract are able to resist bile's antimicrobial effects, relatively little is known about how bile influences virulence of enteric pathogens. Escherichia coli O157:H7 is an important pathogen of humans, capable of causing severe diarrhea and more serious sequelae. In this study, the transcriptome response of E. coli O157:H7 to bile was determined. Bile exposure induced significant changes in mRNA levels of genes related to virulence potential, including a reduction of mRNA for the 41 genes making up the locus of enterocyte effacement (LEE) pathogenicity island. Bile treatment had an unusual effect on mRNA levels for the entire flagella-chemotaxis regulon, resulting in two- to four-fold increases in mRNA levels for genes associated with the flagella hook-basal body structure, but a two-fold decrease for "late" flagella genes associated with the flagella filament, stator motor, and chemotaxis. Bile salts also caused increased mRNA levels for seventeen genes associated with iron scavenging and metabolism, and counteracted the inhibitory effect of the iron chelating agent 2,2'-dipyridyl on growth of E. coli O157:H7. These findings suggest that E. coli O157:H7 may use bile as an environmental signal to adapt to changing conditions associated with the small intestine, including adaptation to an iron-scarce environment.