Altered lipid composition in Streptococcus pneumoniae cpoA mutants

Abstract

BackgroundPenicillin-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.ResultsWe 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.ConclusionsThe 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.

The Pneumococcal Cell Wall

“…Formation of the second major pneumococcal glycolipid α-D-Galp-(1-2)-α-D-Glcp-(1-3)-DAG requires the glycosyltransferase CpoA [100,101]. Interestingly, two piperacillinresistant laboratory mutants of S. pneumoniae R6 have mutations in the cpoA gene and a normal cell-wall choline content [102], suggesting that TAs are present in similar amounts and that the cpoA mutations do not affect TA biosynthesis [101].…”

Enterococcus faecalis Glycolipids Modulate Lipoprotein-Content of the Bacterial Cell Membrane and Host Immune Response

“…Cell membranes of Δ bgsA only contain MGlcDAG and the presence of additional, bilayer forming amphiphiles are most likely needed to dilute the concentration of the non-bilayer forming glycolipid. In Streptococcus pneumoniae , for example, deletion of glycosyltransferase cpoA leads to an arrest of the synthesis of galactosyl-glucosyl-diacylglycerol and to a secondary increase in the proportion of phosphatidylglycerol to cardiolipin [ 50 ]. Lipoproteins also contain large polar head groups and could potentially act as bilayer-prone amphiphiles in the cell membrane of Δ bgsA .…”

Phosphatidylcholine biosynthesis in Mitis group streptococci via host metabolite scavenging

“…S. pneumoniae is a major human pathogen and a close relative of S. mitis . Surprisingly, there are only a few reports on lipid analysis of S. pneumoniae (17–19), for which thin layer chromatography was used as the analytical technique. We applied LC-ESI/MS, with much higher sensitivity and specificity, to investigate the lipidome of S. pneumoniae .…”

“…To our knowledge, this is the first description of PC in S. pneumoniae , a major human pathogen which has been studied for over a century and yet its membrane lipid composition remains poorly understood. There have been very few lipidomic studies performed in S. pneumoniae (17–19), and little is known about how S. pneumoniae remodels its membrane in response to changing environments inside and outside the host. Here, we reported the first identification of PC in S. pneumoniae and demonstrated that S. pneumoniae synthesizes PC only when GPC, a major human metabolite, is available for scavenge.…”

“…Overall, the lipid compositions of streptococci are under-studied and poorly characterized. Previous studies analyzing lipids of streptococci primarily used thin layer chromatography, whose limitations in analytical sensitivity and molecular specificity prohibit comprehensive lipidomic identification; these studies did not detect PC (17–22). However, PC is a biologically significant lipid.…”