Oxidative stress‐induced protein packaging in Enterotoxigenic Escherichia coli outer membrane vesicles and its functional impact on host‐pathogen interactions

Abstract

Enterotoxigenic Escherichia coli is the leading cause of traveler's diarrhea worldwide and it remains an important causal agent of diarrheal disease, especially among children of lower income countries. Because it must adjust to different ecological niches such as fruit and vegetable surfaces, water, and its animal or human host; its cell envelope must undergo remodeling. In Gram‐negative bacteria, the cell envelope is the first barrier against environmental stress and studies have shown that the process of outer membrane vesiculation is essential for bacterial growth and survival during stressful conditions. Recent studies in our lab revealed that outer membrane vesicles (OMVs) can contain varying ratios of lipopolysaccharide (LPS) types during cell envelope remodeling under stress in Salmonella enterica, suggesting a role for vesicles in membrane remodeling. In this study, outer membrane vesicles and outer membrane fractions from ETEC were isolated from bacterial cultures, purified via density centrifugation, and submitted for proteomic analysis using quantitative one‐dimensional liquid chromatography, tandem mass spectrometry (1D‐LC‐MS/MS) to quantify differences in protein expression in vesicles and membranes during oxidizing and non‐oxidizing conditions (plus or minus Hydrogen Peroxide). Protein packaging into vesicles was determined by calculating the log‐2 of the ratio of protein expression in OMVs/outer membranes for both treatment conditions. Results indicated that two distinct sets of proteins were shown to be differentially packaged into OMVs as a function of peroxide treatment. Upon further analysis implementing a Bayesian hierarchical model, lipoproteins were observed to be preferentially exported during stress, in contrast to integral proteins, which were preferentially retained in the outer membrane. Additionally, OMVs derived from stressed cultures showed less cytotoxicity towards Y‐1 adrenal cells in a cell rounding assay. These results allow us to speculate about potential roles for OMVs in membrane remodeling of pathogenic bacteria undergoing environmental shifts both outside and inside the human host.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.