Bovine Bile and Oxygen Availability Impact Escherichia coli O157:H7 Metabolism and Adherence Factor Expression

Escherichia coli O157:H7 represents a major food safety concern, with cattle serving as the primary reservoir host. A better understanding of the interactions between O157 and the potential physiochemical indicators to which it is exposed to in the cattle hindgut would lend insight into the O157 colonization process and aid in the development of effective preharvest interventions to control O157 in its reservoir host. Bovine bile and oxygen are two universal cues that O157 is exposed to upon entry into the cattle hindgut and that vary between different segments of the gastrointestinal tract. Here, we exposed E. coli O157:H7 strain EDL933 to whole bovine bile powder and oxygen, both individually and in combination, and assessed the transcriptomic and phenotypic responses. Under aerobic conditions, EDL933 increased the expression of adiC, and increased biofilm production in vitro, while anaerobic conditions increased the expression of fimbrial genes, including ydeR and fimA. Bovine bile induced the expression of pathways responsible for quorum sensing and the utilization of mucus-derived sugars. These findings suggest that bovine bile and oxygen impact the transcriptomic and phenotypic characteristics of EDL933 in vitro.