Response of Escherichia coli O157 to bovine bile under aerobic and anaerobic conditions

Authors: Maki, Joel; ORTIZ, RANDY - Iowa State University; PEROUTKA-BIGUS, NATHAN - Oak Ridge Institute For Science And Education (ORISE); Loving, Crystal

Submitted to: Conference Research Workers Disease Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 10/30/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Escherichia coli O157 continues to be an important food safety pathogen responsible for significant human disease and economic impacts to the agricultural industry. E. coli O157 asymptomatically colonizes the gastrointestinal tract of ruminants, especially cattle. As part of the initial colonization process, E. coli O157 must sense and respond to various chemical stimuli within the bovine gut, priming it for successful establishment. One commonly encountered chemical signal is bile. Bile is an important indicator for many enteric bacteria, signaling arrival into the gastrointestinal tract and leading to shifts in cell metabolism, expression of colonization factors, and virulence. Another important signal is the oxygen availability in the cattle gastrointestinal tract, which varies both between and within gut compartments and regulates various cellular processes. Understanding the response of E. coli O157 to bovine bile under different levels of oxygenation can provide insights into cell responses in different sections within the bovine gastrointestinal tract and potentially lead to the development of targeted interventions to discourage E. coli O157 colonization in cattle and other ruminants. Here, we investigated the effects of bovine bile powder on E. coli O157 growth and transcriptomic profiles under aerobic and anaerobic conditions. Escherichia coli O157 strain EDL933 was grown to mid-log phase at 39'C in tryptic soy broth (TSB) with and without 0.2% (w/v) dried, unfractionated bovine bile (Millipore Sigma) under aerobic and anaerobic conditions. RNA was extracted (RNeasy kit; Qiagen) and submitted to the Iowa State University Genomics Core Facility for RNAseq on an Illumina NovaSeq 6000 instrument. Resultant reads were analyzed using in silico methods to identify genes and pathways that were enriched and/or depleted under the different conditions tested. The addition of bile powder to culture media impacted growth characteristics of E. coli O157 under aerobic and anaerobic conditions. Differentially expressed genes were observed for both the aerobic and anaerobic bile powder-supplemented conditions, mainly involving metabolism and cell response. Interestingly, genes involved in pilus formation and cell adhesion were significantly upregulated in the aerobic cultures exposed to bovine bile while metabolism and quorum sensing pathways were significantly upregulated in the anaerobic cultures exposed to bovine bile. Growth and transcriptomic profiles of E. coli O157 were impacted by the presence of bovine bile, with metabolic and cell adhesion responses differing based on the presence or absence of oxygen. These observations provide important insights into the E. coli O157 response to bovine bile under different physiological conditions.