Differential View on the Bile Acid Stress Response of Clostridioides difficile.

Susanne Sievers,Christian Wolff,Daniel Troitzsch,Nicole G Metzendorf,Claudia Hirschfeld,Rabea Schlüter,Sophie Marlen Tröger,Daniela Zühlke,Silvia Dittmann,Katharina Riedel,Viola Gast

doi:10.3389/fmicb.2019.00258

Abstract

Clostridioides difficile is an intestinal human pathogen that uses the opportunity of a depleted microbiota to cause an infection. It is known, that the composition of the intestinal bile acid cocktail has a great impact on the susceptibility toward a C. difficile infection. However, the specific response of growing C. difficile cells to diverse bile acids on the molecular level has not been described yet. In this study, we recorded proteome signatures of shock and long-term (LT) stress with the four main bile acids cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), and lithocholic acid (LCA). A general overlapping response to all tested bile acids could be determined particularly in shock experiments which appears plausible in the light of their common steroid structure. However, during LT stress several proteins showed an altered abundance in the presence of only a single or a few of the bile acids indicating the existence of specific adaptation mechanisms. Our results point at a differential induction of the groEL and dnaKJgrpE chaperone systems, both belonging to the class I heat shock genes. Additionally, central metabolic pathways involving butyrate fermentation and the reductive Stickland fermentation of leucine were effected, although CA caused a proteome signature different from the other three bile acids. Furthermore, quantitative proteomics revealed a loss of flagellar proteins in LT stress with LCA. The absence of flagella could be substantiated by electron microscopy which also indicated less flagellated cells in the presence of DCA and CDCA and no influence on flagella formation by CA. Our data break down the bile acid stress response of C. difficile into a general and a specific adaptation. The latter cannot simply be divided into a response to primary and secondary bile acids, but rather reflects a complex and variable adaptation process enabling C. difficile to survive and to cause an infection in the intestinal tract.

Highlights

The anaerobic bacterium Clostridioides difficile represents one of the most serious nosocomial pathogens and is the main cause of antibiotics-associated diarrhea (Thomas et al, 2003)
Species of the intestinal microbiota are capable of deconjugating the primary bile acids, and by dehydroxylation at C7 they can convert CA and chenodeoxycholic acid (CDCA) to secondary bile acids resulting in deoxycholic acid (DCA) and lithocholic acid (LCA), respectively (Figure 1)
Sub-lethal concentrations of the four different bile acids were determined in shock experiments, i e., exponentially growing cells were shocked with concentrations that prevented further growth of C. difficile, but did not cause lysis

Summary

Introduction

The anaerobic bacterium Clostridioides difficile represents one of the most serious nosocomial pathogens and is the main cause of antibiotics-associated diarrhea (Thomas et al, 2003). As an intestinal pathogen C. difficile has to deal with high concentrations of different bile acids, amphiphilic substances with a steroid nucleus (Figure 1). Bile acids are produced by the liver in order to facilitate absorption and digestion of dietary lipids. Due to their soap-like character, bile acids act as natural antimicrobials and only organisms adapted to the challenge will survive in the intestines (Begley et al, 2005). The microbiota largely contributes to the shaping of the intestinal bile acid composition (Long et al, 2017)

Methods

Results

Conclusion