Analysis of Staphylococcus aureus wall teichoic acid glycoepitopes by Fourier Transform Infrared Spectroscopy provides novel insights into the staphylococcal glycocode

Tom Grunert,Monika Ehling-Schulz,Sophia Johler,Dijana Jovanovic,Christopher Weidenmaier,Wanchat Sirisarn,Guoqing Xia

doi:10.1038/s41598-018-20222-6

Abstract

Surface carbohydrate moieties are essential for bacterial communication, phage-bacteria and host-pathogen interaction. Most Staphylococcus aureus produce polyribitolphosphate type Wall teichoic acids (WTAs) substituted with α- and/or β-O-linked N-acetyl-glucosamine (α-/β-O-GlcNAc) residues. GlcNAc modifications have attracted particular interest, as they were shown to govern staphylococcal adhesion to host cells, to promote phage susceptibility conferring beta-lactam resistance and are an important target for antimicrobial agents and vaccines. However, there is a lack of rapid, reliable, and convenient methods to detect and quantify these sugar residues. Whole cell Fourier transform infrared (FTIR) spectroscopy could meet these demands and was employed to analyse WTAs and WTA glycosylation in S. aureus. Using S. aureus mutants, we found that a complete loss of WTA expression resulted in strong FTIR spectral perturbations mainly related to carbohydrates and phosphorus-containing molecules. We could demonstrate that α- or β-O-GlcNAc WTA substituents can be clearly differentiated by chemometrically assisted FTIR spectroscopy. Our results suggest that whole cell FTIR spectroscopy represents a powerful and reliable method for large scale analysis of WTA glycosylation, thus opening up a complete new range of options for deciphering the staphylococcal pathogenesis related glycocode.

Highlights

The Staphylococcus aureus cell envelope comprises a variety of secondary surface glycopolymers including capsule polysaccharide (CP), poly-β(1–6)-N-acetylglucosamine (PNAG), and wall teichoic acid (WTA)[1]
We further demonstrated that highly discriminatory subtyping of S. aureus by Fourier transform infrared (FTIR) spectroscopy primarily relies on the differential expression of capsular serotypes and/or additional surface glycopolymers such as WTA, peptidoglycan, and lipoteichoic acid[15]
Hierarchical cluster analysis (HCA) was carried out to detect inherent spectral differences between wild type strains and strains lacking WTA using the spectral range of 1200–800 cm−1, previously described to be highly discriminatory for S. aureus surface glycostructures

Summary

Introduction

The Staphylococcus aureus cell envelope comprises a variety of secondary surface glycopolymers including capsule polysaccharide (CP), poly-β(1–6)-N-acetylglucosamine (PNAG), and wall teichoic acid (WTA)[1]. These cell surface glycostructures are known to affect bacterial interactions with hosts in multiple ways and are important targets for antimicrobial agents and vaccines[2,3]. Gene transfer (HGT), whereas, a lack in β-O-GlcNAc modification sensitize methicillin resistant S. aureus (MRSA) strains to β-lactams[6,7,9] This variable structure of glycosylated WTA constitutes a specific glycocode and it remains elusive why the presence or absence of both anomeric linkage types differ among clinical isolates. We aim to evaluate the suitability of FTIR spectroscopy as a tool for discrimination of WTA glycoepitopes, between α-O-GlcNAc and β-O-GlcNAc modified WTA

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Conclusion