Formation of acyl phosphatidyl glycerol byEscherichia coli extracts

A Comprehensive Functional Characterization of Escherichia coli Lipid Genes

Lipid membranes are the border between living cells and their environments. The membrane's lipid composition defines fluidity, thickness, and protein activity and is controlled by the intricate actions of lipid gene-encoded enzymes. However, a comprehensive analysis of each protein's contribution to the lipidome is lacking. Here, we present such a comprehensive and functional overview of lipid genes in Escherichia coli by individual overexpression or deletion of these genes. We developed a high-throughput lipidomic platform, combining growth analysis, one-step lipid extraction, rapid LC-MS, and bioinformatic analysis into one streamlined procedure. This allowed the processing of more than 300 samples per day and revealed interesting functions of known enzymes and distinct effects of individual proteins on the phospholipidome. Our data demonstrate the plasticity of the phospholipidome and unexpected relations between lipid classes and cell growth. Modeling of lipidomic responses to short-chain alcohols provides a rationale for targeted membrane engineering.

Metabolic regulations and biological functions of phospholipids in Escherichia coli

Extensive genetic and biochemical studies in the last two decades have elucidated almost completely the framework of synthesis and turnover of quantitatively major phospholipids in E. coli. The knowledge thus accumulated has allowed to formulate a novel working model that assumes sophisticated regulatory mechanisms in E. coli to achieve the optimal phospholipid composition and content in the membranes. E. coli also appears to possess the ability to adapt phospholipid synthesis to various cellular conditions. Understanding of the functional aspects of E. coli phospholipids is now advancing significantly and it will soon be able to explain many of the hitherto unclear cell's activities on the molecular basis. Phosphatidylglycerol is believed to play the central role both in metabolism and functions of phospholipids in E. coli. The results obtained with E. coli should undoubtedly be helpful in the study of more complicated phospholipid metabolism and functions in higher organisms.

Analysis of caulobacter crescentus lipids

The lipids of Caulobacter crescentus, a procaryotic species which differentiates into stalked and swarmer cell types, were analyzed. Major lipid classes were purified by chromatography and identified by both chromatographic and chemical methods. Approximately half of the total lipid fraction of this organism consisted of glycolipis, which were primarily monoglucosyldiglyceride and an acylated glucuronic acid. Two of the phospholipids of C. crescentus were identified as phopshatidylglycerol and acylphosphatidylglycerol. Commonly occurring bacterial phospholipids, such as phosphatidylethanolamine and cardiolipin (diphosphatidylglycerol), were not detected. Monoglyceride and diglyceride were found in the neutral lipid fraction, which made up 10% of the total lipid. Quantitative lipid compositional studies, performed by the incorporation of [14C]acetate and [32P]orthophosphate into growing cultures, revealed that separated swarmer and stalked cells had similar lipid compositions. However, stationary-phase cultures, compared with logaritmic cultures, had decreased amounts of phosphatidylglycerol and diglyceride and increased amounts of acylphosphatidylglycerol and a glucuronic acid-containing glycolipid, glycolipid X. In addition, two glycolipids were only detected in stationary-phase cultures. These studies indicate that C. crescentus has a distinctive lipid composition compared with those of other procaryotic species which have been analyzed.

Calcium-dependent lipolytic acyl-hydrolase activity in purified plant mitochondria

Ageing of isolated potato mitochondria induced by CaCl2 resulted in rapid enzymatic hydrolysis of the membrane phospholipids with the liberation of free fatty acids. The enzyme responsible for this effect was identified as a membrane bound lipolytic acyl-hydrolase which was unmasked by CaCl2. The presence of this lipolytic acyl-hydrolase induced severe functional impairments in the mitochondrial oxidative and phosphorylative properties.

Identification and synthesis of acyl-phosphatidylglycerol in Acinetobacter sp. HO1-N

A minor phospholipid from Acinetobacter sp. HO1-N was identified as acyl-phosphatidylglycerol. Acyl-phosphatidylglycerol synthesis by outer-membrane preparations appeared to be a result of phospholipase A activity.

Novel lipids of Butyrivibrio spp

(1) An analysis has been conducted of the lipids present in three obligately anaerobic bacteria isolated from the ovine rumen belonging to the genus Butyrivibrio. Two of these organisms are rich in phospholipase (A1 + A2) activity, and appear to be different strains of the species fibrisolvens. (2) The only N-containing lipids comprise N-acyl-phosphatidylethanolamine occurring as a minor component in all organisms and a new lipid, diglyceride galactosylphosphorylethanolamine in one of these. (3) All three organisms contained the n-butyryl ester of phosphatidyl-glycerol and in one this represented the major phospholipid present. Valeryl, iso-valeryl, propionyl and myristoyl esters of phosphatidylglycerol were also detected. (4) Two organisms contained glycerylphosphorylgalactosyldiglyceride and one of these also contained a large proportion of a less polar galactophospholipid which is probably a diacyl derivative of the former lipid. (5) All three organisms contained monogalactofuranosyl diglyceride and from one a n-butyryl ester of this galactolipid was isolated. (6) In all of the lipids examined the "diglyceride' moiety consisted almost entirely of plasmalogenic diglyceride (alk-1-enyl, acyl, glycerol).

Studies on the biosynthesis of acylphosphatidylglycerol in Escherichia coli B and B/r

The present study has demonstrated that one molecule of acylphosphatidylglycerol was synthesized from two molecules of phosphatidylgycerol by the transacylation reaction in which phosphatidylglycerol acted both as an acyl donor and an acceptor. Phosphatidylethanolamine was identified as an another acyl donor, participating in acylphosphatidylglycerol formation. These results are discussed in terms of a new pathway for the turnover of phosphatidylglycerol in Escherichia coli.

Phosphatidylglycerol in lung surfactant. II. Subcellular distribution and mechanism of biosynthesis in vitro

Lamellar inclusion bodies, apparent precursors for alveolar surfactant lining, have remarkably similar phospholipid composition to surfactant from alveolar lavage, but distinctly different from other fractions studied: mitochondria, microsomal fraction containing endoplasmic reticulum membranes, plasma membranes and nuclei. Surfactant contained (as % of total phospholipid phosphate): 75.5-77.0% lecithin, 11.0-11.2% phosphatidylglycerol, 4.2-4.6% phosphatidylethanolamine, 3.0-3.2% phosphatidylinositol, 1.5-1.7% bis-(monoacylglycerol) phosphate, 1.2-1.9% phosphatidylserine, and 0.7-1.5% sphingomyelin. Fatty acids of phosphatidylglycerol from lamellar bodies were similar to those from microsomes but different from those in mitochondria. Lung homogenate in continuous sucrose density gradient displayed two major activity peaks of phosphatidylglycerol synthesis: the heavier from mitochondria; the lighter from endoplasmic reticulum. Studies on mechanism of phosphatidylglycerol synthesis in vitro revealed (in these two fractions) CDP-diglyceride and sn-glycerol phosphate precursors to phosphatidylglycerol phosphate, that hydrolysed to phosphatidylglycerol. In microsomes disaturated CDP-diglycerides were 1.6-1.9 times more active substrates than in mitochondria, whereas CDP-diglycerides from egg lecithin were almost equally active. In contrast to lung mitochondria no cardiolipin synthesis was detected in microsomes. The highest specific activities for phosphatidate cytidyltransferase, CDP-diglyceride-inositol phosphatidyltransferase, choline phosphotransferase, and phosphatidylethanolamine methyltransferase were all found in microsomes. The present in vitro studies and additional evidence (M. Hallman and L. Gluck, (1975) Fed. Proc. 34, 274) support the hypothesis that de novo synthesis of surfactant lecithin phosphatidylinositol and phosphatidylglycerol takes place in the endoplasmic reticulum of alveolar cells.

Identification of bisphosphatidic acid and its plasmalogen analogues in the phospholipids of a marine bacterium

A relatively nonpolar unidentified phospholipid (phospholipid X) , isolated from the gram-negative marine bacterium MB 45, was characterized both chromatographically and by chemical analysis. Phospholipid X was shown to be an acidic phospholipid without vicinal hydroxyl, free-amino, or amide groups. The presence of O-alkenyl groups was indicated by a positive reaction for plasmalogen. Mild alkaline methanolysis of phospholipid X yielded only glycerophosphoryglycerol as the derivative. Acetolysis produced only diacyl-glycerol monoacetate. Clevage of O-alkenyl chains by methanolic hydrochloride resulted in the formation of three lyso derivatives. It was estimated that 18.2% of phospholipid X was plasmalogen. From these data, together with chromatographic comparisons with standards, infrared spectra, a molecular weight estimation, and the determination of the glycerol-phosphate-acyl ester ratio, it was concluded that phospholipid X was bisphosphatidic acid mixed with its plasmalogen analogues.

Phospholipid composition and cardiolipin synthesis in fermentative and nonfermentative marine bacteria

Twenty biochemically distinct isolates of marine bacteria, comprising a collection of gram-negative, motile, straight and curved rod-shaped organisms, were separated into fermentative and nonfermentative groups. The isolates were analyzed fro phospholipid composition and the activities of the enzymes, cardiolipin synthetase, and a phosphilipase were determined. The phospholipid compositions of all isolates were generally similar. Phosphatidylethanolamine and phosphatidylglycerol were the major phospholipid classes detected. The absence of cardiolipin in most of the nonfermentative isolates was the most striking observation noted. This was verified chromatographically and by the absence of cardiolipin synthetase activity. In isolates which had cardiolipin, it apparently was synthesized by the condensation of two molecules of phosphatidylglycerol, a mechanism similar to that observed in terrestrial bacteria. Possible correlations between the presence of cardiolipin and Mg-2+ requirements for growth are discussed.