Lipoteichoic acid deficiency permits normal growth but impairs virulence of Streptococcus pneumoniae

Nathalie Heß,Thomas P Kohler,Franziska Waldow,Manfred Rohde,Nicolas Gisch,Torsten Hain,Dominik Schwudke,Alejandro Gómez-Mejia,Sven Hammerschmidt,Bernd Kreikemeyer,Waldemar Vollmer

doi:10.1038/s41467-017-01720-z

Abstract

Teichoic acid (TA), a crucial cell wall constituent of the pathobiont Streptococcus pneumoniae, is bound to peptidoglycan (wall teichoic acid, WTA) or to membrane glycolipids (lipoteichoic acid, LTA). Both TA polymers share a common precursor synthesis pathway, but differ in the final transfer of the TA chain to either peptidoglycan or a glycolipid. Here, we show that LTA exhibits a different linkage conformation compared to WTA, and identify TacL (previously known as RafX) as a putative lipoteichoic acid ligase required for LTA assembly. Pneumococcal mutants deficient in TacL lack LTA and show attenuated virulence in mouse models of acute pneumonia and systemic infections, although they grow normally in culture. Hence, LTA is important for S. pneumoniae to establish systemic infections, and TacL represents a potential target for antimicrobial drug development.

Highlights

Teichoic acid (TA), a crucial cell wall constituent of the pathobiont Streptococcus pneumoniae, is bound to peptidoglycan or to membrane glycolipids
The cell wall was digested with pneumococcal amidase LytA and the resultant peptide-free PGN glycan chains carrying pneumococcal WTA (pnWTA) were isolated by gel permeation chromatography (GPC) (Supplementary Fig. 1a)
The identified molecules correspond to pnWTA chains with five to seven repeating units (RUs) bound by a phosphate moiety to di, tri, or tetramers of MurNAc-GlcNAc disaccharides

Summary

Introduction

Teichoic acid (TA), a crucial cell wall constituent of the pathobiont Streptococcus pneumoniae, is bound to peptidoglycan (wall teichoic acid, WTA) or to membrane glycolipids (lipoteichoic acid, LTA). Like most Gram-positive bacteria S. pneumoniae possesses a lipoteichoic acid (LTA), which is anchored to the cell membrane by a glycolipid moiety. It was suggested that the three LCP proteins attach CPS and TA polymers to PGN, and that the LCP enzymes are required to form the LTA19 Another protein, RafX (SPD_1672 in strain D39, SP_1893 in strain TIGR4), has been proposed to assemble pnWTA based on the reduced amount of WTA detected by an antibody in RafX-deficient strains, which showed impaired colonization capabilities, growth defects, and attenuation in virulence[20,21]. We show that RafX (SPD_1672, SP_1893) is required for the synthesis of pnLTA, but not pnWTA We propose that this protein is most likely involved in ligation of pnTA precursor chains onto the glycolipid anchor, and rename RafX as TacL (for “lipoteichoic acid ligase”). We show that tacL mutants grow with normal rate and morphology in culture but are attenuated in two mouse models of infection

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Conclusion