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Open Access Highly Accessed Research article

Altered lipid composition in Streptococcus pneumoniae cpoA mutants

Marina Meiers1, Carsten Volz12, Jessica Eisel1, Patrick Maurer3, Bernhard Henrich1 and Regine Hakenbeck1*

Author Affiliations

1 Department of Microbiology, University of Kaiserslautern, Gottlieb-Daimler-Strasse, Gebäude 23, D-67663 Kaiserslautern, Germany

2 Present address: Department of Microbial Natural Products, Helmholtz-Institute for Pharmaceutical Research Saarland (HIPS), Saarland University, D-66123 Saarbrücken, Germany

3 Present address: Hochschule für Technik und Wirtschaft des Saarlandes, Goebenstrasse 40, D-66117 Saarbrücken, Germany

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BMC Microbiology 2014, 14:12  doi:10.1186/1471-2180-14-12

Published: 20 January 2014

Abstract

Background

Penicillin-resistance in Streptococcus pneumoniae is mainly due to alterations in genes encoding the target enzymes for beta-lactams, the penicillin-binding proteins (PBPs). However, non-PBP genes are altered in beta-lactam-resistant laboratory mutants and confer decreased susceptibility to beta-lactam antibiotics. Two piperacillin resistant laboratory mutants of Streptococcus pneumoniae R6 contain mutations in the putative glycosyltransferase gene cpoA. The CpoA gene is part of an operon including another putative glycosyltransferase gene spr0982, both of which being homologous to glycolipid synthases present in other Gram-positive bacteria.

Results

We now show that the cpoA mutants as well as a cpoA deletion mutant are defective in the synthesis of galactosyl-glucosyl-diacylglycerol (GalGlcDAG) in vivo consistent with the in vitro function of CpoA as α-GalGlcDAG synthase as shown previously. In addition, the proportion of phosphatidylglycerol increased relative to cardiolipin in cpoA mutants. Moreover, cpoA mutants are more susceptible to acidic stress, have an increased requirement for Mg2+ at low pH, reveal a higher resistance to lysis inducing conditions and are hypersensitive to bacitracin.

Conclusions

The data show that deficiency of the major glycolipid GalGlcDAG causes a pleitotropic phenotype of cpoA mutant cells consistent with severe membrane alterations. We suggest that the cpoA mutations selected with piperacillin are directed against the lytic response induced by the beta-lactam antibiotic.

Keywords:
Streptococcus pneumoniae; Glycolipids; Penicillin resistance; Glycosyltransferase; CpoA; Phospholipid