title: Influence of autoinducer-2 (AI-2) and beef sample extracts on E. coli O157:H7 survival and gene expression of virulence genes yadK and hhA.
abstract: Bacterial cell-to-cell communication is mediated by autoinducer (AI) molecules such as AI-2 and has been reported to regulate gene expression in Escherichia coli O157:H7. We have previously shown that ground beef contains compounds that can inhibit sensing of AI-2 like activity. The hypothesis of this study was that AI-2 activity observed in conditioned medium (CM) will enhance E. coli O157:H7 survival and expression of virulence genes, whereas compounds inhibitory (such as those present in ground beef extracts) to AI-2 activity will negate these effects. E. coli O157:H7 luxS mutant strain VS 94 (incapable of synthesizing AI-2) was employed in these studies. The survival of this enteric bacterial pathogen as a function of AI-2 activity and the presence of AI-2 inhibitory compounds was studied at 4 degrees C. The number of survivors in the presence of AI-2 was significantly higher compared to the absence of AI-2, and the addition of ground beef extracts to conditioned medium negated the influence of AI-2 activity. Autoinducer AI-2 upregulated selected genes virulence genes (yadK, and hha), whereas the ground beef extract reversed the effect of AI-2 on the expression of the selected genes.
authors.affiliation: Department of Poultry Science & Nutrition and Food Science, Texas A & M University, College Station, TX 77843, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Soni
authors.forename: L
authors.initials: L
authors.lastname: Lu
authors.forename: P R
authors.initials: PR
authors.lastname: Jesudhasan
authors.forename: M E
authors.initials: ME
authors.lastname: Hume
authors.forename: S D
authors.initials: SD
authors.lastname: Pillai
mesh_terms: D000818:Animals; D002417:Cattle; D004268:DNA-Binding Proteins; D019453:Escherichia coli O157 / Q000378:metabolism / Q000472:pathogenicity*; D029968:Escherichia coli Proteins; D005516:Food Microbiology; D015964:Gene Expression Regulation, Bacterial; D006714:Homoserine / Q000031:analogs & derivatives* / Q000235:genetics; D006801:Humans; D007783:Lactones; D008461:Meat Products / Q000382:microbiology*; D015398:Signal Transduction; D015854:Up-Regulation; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D007783:Lactones; C091088:N-octanoylhomoserine lactone; D037521:Virulence Factors; C079209:hha protein, E coli; D006714:Homoserine