The role of lipoteichoic acid biosynthesis in membrane lipid metabolism of growing Staphylococcus aureus

Abstract

Pulse-chase experiments with [2-3H]glycerol and [ 14C]acetate revealed that in Staphylococcus aureus lipoteichoic acid biosynthesis plays a dominant role in membrane lipid metabolism. In the chase, 90 % of the glycerophosphate moiety of phosphatidylglycerol was incorporated into the polymer :Glycerophosphodiglucosyldiacylglycerol was shown to be an intermediate, confirming that the hydrophilic chain is polymerized on the final lipid anchor.Total phosphatidylglycerol served as the precursor pool and was estimated to turn over more than twice for lipoteichoic acid synthesis in one bacterial doubling. Of the resulting diacylglycerol approximately 10 %was used for the synthesis of glycolipids and the lipid anchor of lipoteichoic acid. The majority of diacylglycerol recycled via phosphatidic acid to phosphatidylglycerol. Synthesis of bisphosphatidylglycerol was negligible and only a minor fraction of phosphatidylglycerol passed through the metabolically labile lysyl derivative.In contrast to normal growth, energy deprivation caused an immediate switch-over from the synthesis of lipoteichoic acid to the synthesis of bisphosphatidylglycerol.Characteristic lipid amphiphiles of the cytoplasmic membrane of gram-positive bacteria are glycolipids, glycerophosphoglycolipids and lipoteichoic acids which are related to each other (for review see [l]). Most lipoteichoic acids consist of a 1,3-linked poly(g1ycerophosphate) chain which is covalently linked to a particular membrane glycolipid, Glycerophosphoglycolipids are short-chain homologues of lipoteichoic acids as they carry a monoglycerophosphate or di(g1ycerophosphate) residue in place of the poly(g1ycerophosphate) chain on the same glycolipid species. This structural relationship, which also includes the stereochemical configuration of the glycerophosphate residues and the point of attachment at the glycolipid moiety, suggested glycerophosphoglycolipids to be either biosynthetic intermediates or enzymic breakdown products of lipoteichoic acids [l].Labelling experiments in vivo [2, 31, with membrane preparations [4-61 and toluenized cells [7] revealed that lipoteichoic acid biosynthesis occurs through transfer of glycerophosphate from phosphatidylglycerol with the concomitant formation of diacylglycerol. This together with the recent observation that the amount of glycerol in lipoteichoic acid approximately equals that in membrane lipids [l] suggested a substantial effect of lipoteichoic acid synthesis on membrane lipid metabolism. It was the aim of the present study to elucidate this interrelationship. Of particular interest in this context was: (a) the fraction and turnover rate of the phosphatidylglycerol involved, (b) the metabolic fate of the resulting

Synthesis of glycerol phosphate lipoteichoic acid in Staphylococcus aureus

“…Pulse-labeling of staphylococci with [ 14 C]acetate revealed that the label appeared successively in glucosyl diacylglycerol (Glc-DAG), Glc 2 -DAG, and eventually LTA (25). Pulselabeling with [2-3 H]glycerol demonstrated incorporation into PG and glycolipid-anchored LTA (25).…”

“…Pulselabeling with [2-3 H]glycerol demonstrated incorporation into PG and glycolipid-anchored LTA (25). Stepwise degradation of pulse-labeled LTA from the glycerol terminus with phosphodiesterase and phosphomonoesterase revealed that the polymer chain grew distal to the lipid anchor (42,43).…”

“…Although models proposed for the mechanism of LTA synthesis differ, it is commonly accepted that phosphatidyl glycerol (PG) is used as substrate for polyglycerol phosphate LTA synthesis (25)(26)(27). Werner Fischer proposed a model whereby LTA is polymerized on the outer surface of bacterial membranes (26).…”

Small and medium‐angle X‐ray analysis of bacterial lipoteichoic acid phase structure

“…3. Based on the average diameter of a lipoteichoic acid micelle, a number of related molecular properties can be estimated by using the following additional information: (a) as the diacylglycerol anchor of the lipoteichoic acid is derived from diacylglycerol from membranelipid metabolism [6], the diameter of the lipid core region of the lipoteichoic acid micelle can be estimated to amount of approximately 5 nm (= 2 rL, Fig. 3); (b) since the fatty acid chains of the lipoteichoic acid were found in the molten conformation, the area occupied by the lipid anchor at a distance rL from the center of the micelle should be in the order of approximately 0.5 nm2 1261; (c) the average hydrophilic chain of the staphylococcal lipoteichoic acid comprises about 25 glycerophosphate units [6].…”

“…Based on the average diameter of a lipoteichoic acid micelle, a number of related molecular properties can be estimated by using the following additional information: (a) as the diacylglycerol anchor of the lipoteichoic acid is derived from diacylglycerol from membranelipid metabolism [6], the diameter of the lipid core region of the lipoteichoic acid micelle can be estimated to amount of approximately 5 nm (= 2 rL, Fig. 3); (b) since the fatty acid chains of the lipoteichoic acid were found in the molten conformation, the area occupied by the lipid anchor at a distance rL from the center of the micelle should be in the order of approximately 0.5 nm2 1261; (c) the average hydrophilic chain of the staphylococcal lipoteichoic acid comprises about 25 glycerophosphate units [6]. From simple geometrical considerations the following conclusions can be drawn: (a) each micelle is on average made up by about 150 lipoteichoic acid molecules, (b) the surface area available for each hydrophobic lipoteichoic acid chain amounts to approximately 10 nm2 at the surface of the micelle, (c) the outer hydrophilic shell of the micelle is heavily hydrated (nearly 80% of the volume of the outer shell is occupied by water), and (d) the hydrophilic poly(g1ycerophosphate) chains of the lipoteichoic acid exist in a heavily coiled conformation (the length of a fully extended chain consisting of 25 subunits would be in the order of 17.5 nm as compared to the estimated 8.5 nm thickness of the hydrophilic shell of the lipoteichoic acid micelle).…”