Proteomic analysis of enterotoxigenic Escherichia coli (ETEC) in neutral and alkaline conditions

Lucia Gonzales-Siles,Roger Karlsson,Åsa Sjöling,Anders Karlsson,Diarmuid Kenny

doi:10.1186/s12866-016-0914-1

Lucia Gonzales-Siles, Roger Karlsson + Show 3 more

Open Access

https://doi.org/10.1186/s12866-016-0914-1

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Journal: BMC Microbiology	Publication Date: Jan 7, 2017
Citations: 12	License type: open-access

Affiliation: Karolinska Institutet, University of Gothenburg

Abstract

BackgroundEnterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in children and travelers to endemic areas. Secretion of the heat labile AB5 toxin (LT) is induced by alkaline conditions. In this study, we determined the surface proteome of ETEC exposed to alkaline conditions (pH 9) as compared to neutral conditions (pH 7) using a LPI Hexalane FlowCell combined with quantitative proteomics. Relative quantitation with isobaric labeling (TMT) was used to compare peptide abundance and their corresponding proteins in multiple samples at MS/MS level. For protein identification and quantification samples were analyzed using either a 1D-LCMS or a 2D-LCMS approach.ResultsStrong up-regulation of the ATP synthase operon encoding F1Fo ATP synthase and down-regulation of proton pumping proteins NuoF, NuoG, Ndh and WrbA were detected among proteins involved in regulating the proton and electron transport under alkaline conditions. Reduced expression of proteins involved in osmotic stress was found at alkaline conditions while the Sec-dependent transport over the inner membrane and outer membrane protein proteins such as OmpA and the β-Barrel Assembly Machinery (BAM) complex were up-regulated.ConclusionsETEC exposed to alkaline environments express a specific proteome profile characterized by up-regulation of membrane proteins and secretion of LT toxin. Alkaline microenvironments have been reported close to the intestinal epithelium and the alkaline proteome may hence represent a better view of ETEC during infection.

Highlights

Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in children and travelers to endemic areas
In this study we analyzed the proteome of ETEC exposed to alkaline conditions as compared to neutral conditions in order to further determine the effect of highly alkaline conditions on ETEC
Surface proteome analysis and protein annotation To study the effect of alkaline pH on ETEC strain E2863 we used a Tandem mass spectrometry (MS)-based quantitative proteomic strategy

Summary

Introduction

Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in children and travelers to endemic areas. The two major ETEC toxins, heat labile toxin (LT) and heat stable toxin (ST), binds to enteric receptors on the epithelium and cause de-regulation of the chloride channel CFTR, which leads to increased secretion of chloride ions, bicarbonate and electrolytes [3]. ETEC encounter different environments in the human gastrointestinal tract before reaching optimal conditions for infection in the small intestine and environmental cues, such as bile, oxygen and pH affect secretion of toxins and virulence of ETEC [7, 11, 12]. Further down in the anaerobic gut the pH is expected to drop to acidic levels again but close to the small intestinal epithelium alkaline conditions can occur due to release of bicarbonate. In this study we analyzed the proteome of ETEC exposed to alkaline conditions (pH 9) as compared to neutral conditions (pH 7) in order to further determine the effect of highly alkaline conditions on ETEC

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