Bovine bile and oxygen availability impact Escherichia coli O157:H7 metabolism and adherence factor expression

Authors: Maki, Joel; ORTIZ, RANDY - Oak Ridge Institute For Science And Education (ORISE)

Submitted to: Bacteria
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2026
Publication Date: 8/1/2026
Citation: Maki, J.J., Ortiz, R. 2026. Bovine bile and oxygen availability impact Escherichia coli O157:H7 metabolism and adherence factor expression. Bacteria. 5(3):44. https://doi.org/10.3390/bacteria5030044.
DOI: https://doi.org/10.3390/bacteria5030044

Interpretive Summary: Escherichia coli O157:H7 (O157) remains a significant food safety concern, with cattle serving as its primary reservoir. Understanding how O157 colonizes the bovine gut is essential for identifying the chemical and biological factors that enable successful colonization in order to develop targeted preharvest interventions. Upon entering the cattle intestine, O157 is consistently exposed to both bile and oxygen, so these factors could influence its colonization strategy. Here, we exposed a strain of O157 to bovine biler and oxygen, both individually and in combination. Exposure to oxygen enhanced the ability of O157 to form protective biofilms and upregulated genes involved in attaching to bovine intestinal cells in vitro. Exposure to bovine bile stimulated metabolic pathways that allow O157 to utilize mucus-derived sugars, which are abundant nutrient sources in the cattle intestine. Together, these results demonstrate that bovine bile and oxygen each modulate O157 colonization mechanisms, positioning both as critical environmental cues to target for developing effective preharvest interventions that can reduce contamination food product contamination, lower industry costed associated with O157 control, and protect consumers from foodborne illness.

Technical Abstract: 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 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 which 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 expression of adiC, and increased biofilm production in vitro, while anaerobic conditions increased expression of fimbrial genes, including ydeR and fimA. Bovine bile induced expression of pathways responsible for quorum sensing and the utilization of mucus-derived sugars. These findings suggest that both bovine bile and oxygen presence have significant impacts on the transcriptomic and phenotypic characteristics of EDL933, implying both may serve as important cues for EDL933 as it colonizes the cattle hindgut.