Modification of the fatty acid composition of individual phospholipids and neutral lipids after infection of the simian erythrocyte by Plasmodium knowlesi

Using capillary gas-liquid chromatography, we have analyzed the alteration in the total fatty acid, phospholipid and neutral lipid compositions of the monkey erythrocyte, after infection by the malarial parasite Plasmodium knowlesi. Data based on fatty acid quantitation show that the phospholipid composition is altered, with particularly large increases in phosphatidylcholine (PC) and phosphatidylethanolamine (PE), the most abundant phospholipids in normal and P. knowlesi-schizont-infected cells. Unesterified fatty acids were found to be less abundant in infected cells. The total fatty acid content of the cell is increased 6-fold during infection, and total fatty acid composition is also changed: the infected cells are richer in palmitate (+23%), oleate (+29%) and linoleate (+89%), but contained less stearate (-27%) and arachidonate (-40%). The determination of the fatty acid composition of individual phospholipids, neutral lipids and unesterified fatty acids showed that choline-containing phospholipids (PC and sphingomyelin) were not as altered in their fatty acid pattern as anionic phospholipids (PE, phosphatidylserine (PS) and phosphatidylinositol (PI) and lysophosphatidylcholine (lysoPC). Specific alterations in the fatty acid compositions of individual phospholipids were detected, whereas the rise in linoleic acid was the only change during infection that was recovered in each phospholipid (except PC), neutral lipid and unesterified fatty acids. The fatty acid composition of the neutral lipids and unesterified fatty acids was particularly modified: the only rise in arachidonic acid level was observed in these lipid classes after infection. The total plasmalogen level of the erythrocyte is decreased in infected cells (-60%), but their level is increased in PI.     

Lipid composition of lysosomal multilamellar bodies of male mouse urine

Previous studies from our laboratory have shown that male C57BL/6J mice excrete into the urine multilamellar lysosomal bodies that contain specific neutral glycosphingolipids. These mice excrete approximately 20-30% of their kidney glycolipids each day. The significance and function of this secretion of multilamellar lysosomal organelles is unknown. To characterize these excreted bodies further, we report here their neutral lipid and phospholipid composition. The bodies were collected by differential centrifugation, extracted with chloroform-methanol, and lipids were fractionated into neutral lipids, glycolipids, and phospholipids. The neutral lipids consisted primarily of cholesterol, dolichol, and ubiquinone. The phospholipid fraction consisted primarily of a single molecular species of phosphatidylcholine. This lipid which comprises more than 90% of the total phospholipids was found to contain 16:0 ether and C22:6 n-3 fatty acid as determined by gas-liquid chromatography-mass spectrometry. The glycosphingolipids as reported previously consisted primarily of galabiosylceramides and globotriaosylceramides. This membrane lipid composition is different from any previously reported cellular organelle.     

Isolation and composition of the carotenoid-containing oil droplets from cone photoreceptors.

A procedure for isolating the carotenoid-containing oil droplets of cone retinal photoreceptors of Gallus domesticus is described. The oil droplets, composed almost entirely of neutral lipids and carotenoids, have been separated into ten chromatographic components. Similar separations have been carried out on the total retinal neutral lipids for comparison. The neutral lipids represented 26.1% of the total retinal lipid. Cholesterol, cholesterol ester, mono-, di- and triacylglycerols represented 92.6% of the total neutral lipid. Each of these and other minor neutral lipid components were also present in the lipids extracted from the isolated oil droplets in correspondingly similar concentrations. However, the concentrations of carotenoids were greatly enriched in the neutral lipids of the oil droplets. Each of the major fatty acyl-containing neutral lipids from the chromatography of oil droplet lipids is greatly enriched in polyunsaturated fatty acids when compared with the corresponding component from the total neutral lipid chromatography. In the acylglycerols and free fatty acid fraction from the oil droplets, linoleic and arachidonic acid together represented 52-83% of the total polyunsaturated fatty acids present. The remainder was generally distributed about equally among six other acids. Except for the diacylglycerol fraction, linoleic acid was usually the most enriched acid in a specific oil droplet fraction when compared with any other polyunsaturated fatty acids. A similar pattern of polyunsaturated fatty acid enrichment observed in the fatty acids of the outer segment phospholipids relative to the corresponding total phospholipid fractions of this cone rich retina (Johnston, D. and Hudson, R.A. (1974) Biochim. Biophys. Acta 369, 269) suggest possible metabolic relationships between the oil droplet neutral lipids and the outer segment membrane phospholipids of the cone photoreceptors. A mechanism for the accumulation of the carotenoids in the oil droplets is also discussed.     

Uptake and interconversion of fluorescent lipid analogs in the protozoan parasite, Perkinsus marinus, of the oyster, Crassostrea virginica

Uptake, distribution, and interconversion of fluorescent lipid analogs (phosphatidylcholine, PC; cholesteryl ester, CHE; phosphatidylethanolamine, PE; palmitic acid, C16; sphingomyelin, SM) by the two life stages, meront and prezoosporangium, of the oyster protozoan parasite, Perkinsus marinus, were investigated. Class composition of these two life stages and lipid contents in meront cells were also examined. Both meronts and prezoosporangia incorporated and modified fluorescent lipids from the medium, but their metabolic modes differ to some extent. Results revealed that among the tested analogs, neutral lipid components (CHE and C16) were incorporated to a greater degree than the phospholipids (PC, PE, and SM). HPLC analysis of meront lipids showed that while the majority of the incorporated PC, CHE, and PE remained as parent compounds, most of the incorporated C16 was in triacylglycerol (TAG) and SM was in ceramide and free fatty acids. The cellular distribution of fluorescent labels varied with lipid analogs and the extent of their metabolism by the parasite. Fluorescence distribution was primarily in cytoplasmic lipid droplets of both life stages after 24 h incubation with PC. After 24 h incubation with SM, fluorescence appeared in the membrane and cytosol. Total lipid contents in meront cultures increased during proliferation and TAG accounted for most of the increased total lipids. Since total lipid content per meront cell did not increase until the day of culture termination, the lipid increase in the meront culture was mainly a result of increased cell numbers. Both life stages contain relatively high levels of phospholipids, 53.8% in 8-day-old meronts and 39.4% in prezoosporangia. PC was the predominant phospholipid.     

脂滴——细胞脂类代谢的细胞器

脂滴是细胞内中性脂贮存的主要场所,由极性单磷脂层包裹疏水核心组成。近年来的蛋白质组学研究表明,脂滴表面还存在着许多功能蛋白,进一步揭示了脂滴可能参与细胞内物质的代谢和转运,以及细胞信号传导等过程,是一个活动旺盛的多功能细胞器。实验结果还证明,脂滴不但是甘油三酯贮存和分解、花生四烯酸代谢和前列腺素合成的主要场所,脂滴还具有合成甘油三酯和磷酯的功能。由此可见,脂滴可能是细胞内参与脂类合成代谢的细胞器。     

Lipid changes of goat sperm plasma membrane during epididymal maturation

Highly purified plasma membranes of maturing goat caput-, corpus- and cauda-epididymal spermatozoa were isolated by aqueous two-phase polymer methods and their lipid constituents were analysed. Phospholipid (approx. 75% w/w), neutral lipid (approx. 15% w/w) and glycolipid (approx. 10% w/w) were the major sperm membrane lipids. There was a significant decrease in the total lipids (approx. 25% w/w), phospholipid (approx. 30% w/w) and glycolipid (approx. 80% w/w) contents of sperm membrane during epididymal maturation. On the contrary, the mature cauda-sperm membrane showed greater (approx. 50% w/w) neutral lipid content than that of the immature caput sperm. Phosphatidylcholine (PC), phosphatidylethanolamine (PE) and sphingomyelin were the phospholipids of the sperm membrane, the former two being the major lipids. Both PC and PE fractions consisted of three species--diacyl, alkylacyl and alkenylacyl forms, the last one being the dominant species in both PC and PE. Of all the phospholipids, diacyl PE decreased most strikingly (approx. 65% w/w) during sperm maturation. The neutral lipid fraction contained sterols, wax esters, 1-O-alkyl-2,3-diacylglycerol, triacylglycerol and fatty acids. Sterols represented nearly 75% w/w of the neutral lipids and cholesterol was the major component (approx. 95% w/w) of the sterol fraction. The sperm maturity was associated with marked increase of sterol (approx. 60% w/w) and steryl ester (approx. 200% w/w) and decrease (approx. 50-65% w/w) of the other membrane-bound neutral lipids. The glycolipid was identified as monogalactosyldiacylglycerol. The fatty acid profile of the various membrane lipids underwent marked alteration during the epididymal transit of the male gametes. Cholesterol/phospholipid and saturated/unsaturated fatty acid ratios increased greatly in the maturing sperm membrane. The altered lipid profile of the mature sperm membrane leads to changes in its fluidity that play an important role in determining the structure and functions of the biomembrane.     

Lipid droplets as dynamic organelles connecting storage and efflux of lipids

Neutral lipids are stored in the cytosol in so-called lipid droplets. These are dynamic organelles with neutral lipids as the core surrounded by a monolayer of amphipathic lipids (phospholipids and cholesterol) and specific proteins (PAT proteins and proteins involved in the turnover of lipids and in the formation and trafficking of the droplets). Lipid droplets are formed at microsomal membranes as primordial droplets with a diameter of 0.1-0.4 microm and increase in size by fusion. In this article, we review the assembly and fusion of lipid droplets, and the processes involved in the secretion of triglycerides. Triglycerides are secreted from cells by two principally different processes. In the mammary gland, lipid droplets interact with specific regions of the plasma membrane and bud off with an envelope consisting of the membrane, to form milk globules. In the liver and intestine, very low-density lipoproteins (VLDL) and chylomicrons are secreted by using the secretory pathway of the cell. Finally, we briefly review the importance of lipid droplets in the development of insulin resistance and atherosclerosis.     

The relationship between plasma membrane lipid composition and physical-chemical properties. III. Detailed physical and biochemical analysis of fatty acid-substituted EL4 plasma membranes

Murine leukemia EL4 cells were modified by supplementation of culture media with fatty acids for 24 h. A plasma membrane-enriched fraction was prepared from substituted and normal cells. Analyses were performed to determine fatty acyl composition, phospholipid headgroup composition and cholesterol content. The two major membrane phospholipids, phosphatidylethanolamine (PE) and phosphatidylcholine (PC) were isolated by thin-layer chromatography and ESR measurements were done on liposomes prepared from these lipids as well as on the intact plasma membrane preparations. Slight perturbations in overall plasma membrane lipid composition were observed when EL4 cells were supplemented with a single exogenous fatty acid. This may be consistent with the idea that the incorporation of exogenous fatty acid induces compensatory changes in membrane lipid composition. On the other hand, we observed no significant difference in two ESR motional parameters between the unsubstituted control and various fatty acid-substituted plasma membranes. ESR measurements carried out on PE and PC liposomes derived from 17:0- and 18:2c-substituted membranes also failed to detect major differences between these liposomes and those made from normal EL4 phospholipids. In the case of liposomes prepared from 18:2t,-substituted membranes, the order parameter was significantly changed from the normal. However, the change was in opposite directions in PE and PC, perhaps accounting for the fact that no change parameter is seen in intact 18:2t-substituted plasma membrane. Measurements of order parameter (S) in mixed lipid vesicles showed that at up to 50 mol% mixture of a synthetic PC with plasma membrane PC, the value of S was only marginally different from that of the plasma membrane PC vesicles. We interpret these data as an indication that the two ESR parameters used are not sufficiently sensitive to detect changes due to modifications of the acyl chain composition of a complex biological membrane.     

Lipid composition of lymphocyte plasma membrane from pig mesenteric lymph node.

1. The lipid fraction of the plasma membrane of pig mesenteric lymph-node lymphocytes contained primarily (94%) neutral lipids and phospholipids in about equal weights. The remianing lipid comprised glycosphingolipids (1.8%), gangliosides (o.27%)and probably ceramides (1.3%).The major phospholipid was phosphatidylcholine (46% of the total), and mono- and tri-hexosylceramides accounted for 72% of the glycosphingolipids. Haematoside was distributed between the glycosphingolipid and ganglioside fractions. The major ganglioside was monosialoganglioside. About 90% of the sialic acid was N-glycollylated. 2. A comparision of the lipid composition of the plasma-membrane fraction with that of the initial lymph-node homogenate showed that the purified membrane contained increased proportions of phospholipids, especially sphingomyelin, glycosphingolipids and gangliosides. 3. Fatty acid analyses showed that the membrane phosphatidylcholine was rich in palmitic acid, that the sphingomeyelin and phosphatidylethanolamine were high in myristic acid and that the glycosphingolipids were rich in oleic acid.     

Presence of phospholipid-neutral lipid complex structures in atherosclerotic lesions as detected by a novel monoclonal antibody.

A novel monoclonal antibody (ASH1a/256C) that recognizes atherosclerotic lesions in human and Watanabe heritable hyperlipidemic (WHHL) rabbit aortae is described. When (123)I-labeled ASH1a/256C antibody is injected intravenously into WHHL rabbits, it associates specifically with fatty streaks on the aorta. The antigen recognized by the antibody is lipid, based on extraction with chloroform and methanol from WHHL rabbit tissues. The antigen, purified by high performance liquid chromatography, was shown to be phosphatidylcholine (PC), which contains unsaturated fatty acyl groups based on analyses utilizing (1)H and (13)C nuclear magnetic resonance, Fourier transfer-infrared spectrum, and mass spectrometry. The antibody did not react with other classes of phospholipids or neutral lipids when tested using an enzyme-linked immunosorbent assay. When PC was mixed with either cholesterol, cholesteryl ester, or triacylglycerol, however, the reactivity of the antibody to PC increased up to 8-fold. Homogenates of aorta tissue obtained from normal and WHHL rabbits were fractionated using sucrose density gradient ultracentrifugation in which neutral lipid droplets, cellular membranes, and proteins are separated. The phospholipid content in cellular membrane fractions from WHHL rabbits was twice as high as that of normal rabbits, and there was an enormous difference in the antigenic activity in these fractions. The content of cholesterol in the cellular membrane fraction of WHHL rabbits was approximately 50 times higher than that of normal rabbits. Addition of neutral lipids to the cellular membrane fraction of normal rabbit markedly increased the antigenic activity. Atheromatous lesions in thickened WHHL rabbit aortic intima that were rich in lipid droplets were stained positively with ASH1a/256C immunohistochemically. These results strongly suggest that PC-neutral lipid complex domains are formed in atherosclerotic lesions.     

Plasma and muscle phospholipids are involved in the metabolic response to long-distance migration in a shorebird

We studied: (1) concentrations and fatty acid compositions of plasma non-esterified fatty acids, neutral lipids, and phospholipids, and (2) fatty acid composition of flight muscle phospholipids in wintering, premigratory, and spring and fall migrating western sandpipers ( Calidris mauri). Plasma neutral lipid and phospholipid levels were elevated in migrants, reflecting high rates of fat deposition. An important role of phospholipids in fattening is suggested by the fact that the amount of fatty acids in plasma phospholipids was similar to, or in spring as much as twice, that of neutral lipids. Changes in the ratio of plasma neutral lipids to phospholipids may indicate seasonal changes in triacylglycerol stores of invertebrate prey. Monounsaturation and total unsaturation of plasma neutral lipids and phospholipids increased during migration. Muscle phospholipids were more monounsaturated in spring and fall, but total unsaturation was reduced in fall. Arachidonic acid [20:4(n-6)] was especially abundant in muscle phospholipids in winter (29%) and declined during migration (19-22%), contributing to a decline in the ratio of n-6 to n-3 fatty acids. The abundance of plasma phospholipids and variability of neutral lipid to phospholipid ratio indicates that measurement of plasma phospholipids will improve methods for assessment of fattening rates of birds. The functional significance of changes in muscle phospholipids is unclear, but may relate to depletion of essential n-6 fatty acids during exercise.     

Presence of anionic phospholipids rules the membrane localization of phenothiazine type multidrug resistance modulator

Substances able to modulate multidrug resistance (MDR), including antipsychotic phenothiazine derivatives, are mainly cationic amphiphiles. The molecular mechanism of their action can involve interactions with transporter proteins as well as with membrane lipids. The interactions between anionic phospholipids and MDR modulators can be crucial for their action. In present work we study interactions of 2-trifluoromethyl-10-(4-[methanesulfonylamid]buthyl)-phenothiazine (FPhMS) with neutral (PC) and anionic lipids (PG and PS). Using microcalorimetry, steady-state and time-resolved fluorescence spectroscopy we show that FPhMS interacts with all lipids studied and drug location in membrane depends on lipid type. The electrostatic attraction between drug and lipid headgroups presumably keeps phenothiazine derivative molecules closer to surface of negatively charged membranes with respect to neutral ones. FPhMS effects on bilayer properties are not proportional to phosphatidylserine content in lipid mixtures. Behavior of equimolar PC:PS mixtures is similar to pure PS bilayers, while 2:1 or 1:2 (mole:mole) PC:PS mixtures resemble pure PC ones.     

Incorporation of radioiodinated fatty acids into cardiac phospholipids of normoxic canine myocardium

The aim of this study was to assess the phospholipid distribution of radioiodinated 17-iodoheptadecanoic acid (IHDA), 15-(p-iodophenyl)pentadecanoic acid (p-IPPA) and 15-(p-iodophenyl)-3,3-dimethylpentadecanoic acid (DMIPPA) under normoxic conditions and to compare these data with the fatty acid composition of the phospholipid classes. After simultaneous i.v. injection of the radioiodinated fatty acids (1-123-IHDA; 1-131-p-IPPA; 1-125 DMIPPA) in open-chest dogs seven myocardial biopsies were taken over 40 min (n = 26). After lipid extraction of the biopsies the organic phase was analyzed for both neutral and polar lipids by two different TLC systems. The following polar lipid fractions were analyzed: lysophopshatidylcholine (LPC), sphingomyelin (SPH), phosphatidy1choline (PC; lecithin), phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), diphosphatidylglycerol (DPG; cardiolipin) and neutral lipids. Fractions were counted in a gamma well counter and corrected for cross-over and recovery. Results of the polar phospholipids analysis showed that IHDA has the highest incorporation into the phospholipids. The IHDA was mainly incorporated into PI (45.6%) followed by PC (30.9%), PE (14.0%) and PS (5.6%). The p-IPPA was predominantly incorporated incorporated into PC (37.2%), followed by PS (20.1%) and PE (13.7%). In contrast to IHDA, incorporation of p-IPPA into PI was small (6.4%). The DMIPPA analogue was incorporated into phopsholipids to only a very small degree, compared to IHDA and p-IPPA. PS (27.4%) was the only considerable phospholipid fraction into which DMIPPA was incorporated.The results clearly demonstrated that these radioiodinated fatty acid analogues have entirely different patterns of phospholipid incorporation. Major resemblances have been found between the incorporation into phospholipids of IHDA and the phospholipid distribution of the natural counterpart: stearic acid. The p—IPPA phospholipid incorporation only partly resembles the phospholipid distribution of palmitic acid. DMIPPA is because of its modified structure, incorporated into phospholipids to a low extent, mainly into PS. (Mol Cell Biochem116: 79–87, 1992)     

Lipid requirement of the branched-chain amino acid transport system of Streptococcus cremoris

The role of the membrane lipid composition on the transport protein of branched-chain amino acids of the homofermentative lactic acid bacterium Streptococcus cremoris has been investigated. The major membrane lipid species identified in S. cremoris were acidic phospholipids (phosphatidylglycerol and cardiolipin), glycolipids, and glycerophosphoglycolipids. Phosphatidylethanolamine (PE) was completely absent. Protonmotive force-driven and counterflow transport of leucine was assayed in fused membranes of S. cremoris membrane vesicles and liposomes composed of different lipids obtained by the freeze/thaw-sonication technique. High transport activities were observed with natural S. cremoris and Escherichia coli lipids, as well as with mixtures of phosphatidylcholine (PC) with PE or phosphatidylserine. High transport activities were also observed with mixtures of PC with monogalactosyl diglyceride, digalactosyl diglyceride, or a neutral glycolipid fraction isolated from S. cremoris. PC or mixtures of PC with phosphatidylglycerol, phosphatidic acid, or cardiolipin showed low activities. In mixtures of PC and methylated derivatives of PE, both counterflow and protonmotive force-driven transport activities decreased with increasing degree of methylation of PE. The decreased transport activity in membranes containing PC could be restored by refusion with PE-containing liposomes. These results demonstrate that both aminophospholipids and glycolipids can be activators of the leucine transport system from S. cremoris. It is proposed that aminophospholipids in Gram-negative bacteria and glycolipids in Gram-positive bacteria have similar functions with respect to solute transport.     

A novel fluorescent fatty acid, 5-methyl-BDY-3-dodecanoic acid, is a potential probe in lipid transport studies by incorporating selectively to lipid classes of BHK cells.

The 5-methyl-BDY-3-dodecanoic acid (B12FA) labelling of BHK cell lipids was analyzed by thin layer and reverse phase column chromatography. Incorporation to phospholipids was selective: over 90% of B12FA label was enriched in phosphatidylcholine. The major molecular species of PC was that containing palmitate as the unlabelled fatty acid. Small amounts of label was also found in other phosphoglycerides, but not in sphingomyelin. Triglycerides and diglycerides constituted the main B12FA-labelled neutral lipid classes; however, no label was found in cholesterol esters. B12FA was degraded to shorter homologues, which had significantly slower lipid incorporation rates. B12FA-labelled cells displayed in a microscope initially green reticular type fluorescence, but later red spherical structures, representing neutral lipid droplets, could also be seen. It is concluded that B12FA does not incorporate indiscriminately to all lipid classes of BHK cells, but is enriched to PC, diglycerides and triglycerides, which could be utilized in studies on lipid transport as well as metabolism.     

Lipid composition of a plasma membrane enriched fraction of maize roots

The lipid composition of a plasma membrane enriched fraction isolated from corn (Zea mays) roots was examined. On a wt basis, the lipid: protein ratio was 1.11. Phospholipids comprised 60% of total lipids with the major phospholipids being phosphatidylcholine (62%) and phosphatidylethanolamine (21%). Free sterol was the major neutral lipid. The sterol:phospholipid molar ratio was 0.31. The fatty acid composition of the membrane was predominantly linoleic (60%) and palmitic (30%).     

Detergent-resistant membrane fractions contribute to the total 1H NMR-visible lipid signal in cells.

Leukocytes and other cells show an enhanced intensity of mobile lipid in their 1H NMR spectra under a variety of conditions. Such conditions include stimulation, which has recently been shown to involve detergent-resistant, plasma membrane domains (DRMs) often called lipid rafts. As there is much speculation surrounding the origin of cellular NMR-visible lipid, we analysed subcellular fractions, including DRMs, by NMR spectroscopy. We demonstrated that DRMs isolated by density gradient centrifugation from lymphoid (CEM-T4, stimulated Jurkat cells), and monocytoid (THP-1) cells produced NMR-visible, lipid signals. Large scale subfractionation of THP-1 cells determined that while cytoplasmic lipid droplets constituted much of the total NMR-visible lipid, the contribution of DRMs was significant. Qualitative and quantitative lipid analyses revealed that DRMs and lipid droplets differed in their lipid composition. DRMs were enriched in cholesterol and ganglioside GM1, and contained relatively unsaturated fatty acids compared with the lipid droplets. Both lipid droplets and DRMs contained neutral lipids (triacylgycerols, cholesterol ester, fatty acids in THP-1 cells) that could, in addition to phospholipids, contribute to the NMR-visible lipid. The lipid droplets also exhibited different protein profiles and contained 500-fold less protein than DRMs, confirming that DRMs and droplets were fractionated as separate entities. The NMR-visible lipid in DRMs is therefore unlikely to be a contaminant from lipid droplets. We propose a micropartitioning of the NMR-visible mobile lipid of whole cells between intracellular lipid droplets, where most of this lipid resides, and detergent-resistant plasma membrane domains.     

Dictyostelium Lipid Droplets Host Novel Proteins

Across all kingdoms of life, cells store energy in a specialized organelle, the lipid droplet. In general, it consists of a hydrophobic core of triglycerides and steryl esters surrounded by only one leaflet derived from the endoplasmic reticulum membrane to which a specific set of proteins is bound. We have chosen the unicellular organism Dictyostelium discoideum to establish kinetics of lipid droplet formation and degradation and to further identify the lipid constituents and proteins of lipid droplets. Here, we show that the lipid composition is similar to what is found in mammalian lipid droplets. In addition, phospholipids preferentially consist of mainly saturated fatty acids, whereas neutral lipids are enriched in unsaturated fatty acids. Among the novel protein components are LdpA, a protein specific to Dictyostelium, and Net4, which has strong homologies to mammalian DUF829/Tmem53/NET4 that was previously only known as a constituent of the mammalian nuclear envelope. The proteins analyzed so far appear to move from the endoplasmic reticulum to the lipid droplets, supporting the concept that lipid droplets are formed on this membrane.     

Evidence for a Composite State of an F′his,gnd Element and a Cryptic Plasmid in a Derivative of Salmonella typhimurium LT2

The zoospores of Blastocladiella emersonii, when derived from cultures grown on solid media, contain about 11% total lipid. This lipid was separated chromatographically on silicic acid into neutral lipid (46.6%), glycolipid (15.8%), and phospholipid (37.6%). Each class was fractionated further on columns of silicic acid, Florisil, or diethylaminoethyl-cellulose, and monitored by thin-layer chromatography. Triglycerides were the major neutral lipids, mono- and diglycosyldiglycerides were the major glycolipids, and phosphatidylcholine and phosphatidylethanolamine were the major phospholipids. Other neutral lipids and phospholipids detected were: hydrocarbons, free fatty acids, free sterols, sterol esters, diglycerides, monoglycerides, lysophosphatidylcholine, lysophosphatidylethanolamine, phosphatidic acid, phosphatidylserine, and phosphatidylinositol. Palmitic, palmitoleic, stearic, oleic, gamma-linolenic, and arachidonic acids were the most frequently occurring fatty acids. When B. emersonii was grown in (14)C-labeled liquid media, lipid again accounted for 11% of both mature plants and zoospores released from them. The composition of the lipid extracted from such plants and spores was also the same; however, it differed markedly from that of the lipid in spores harvested from solid media, consisting of 28.3% neutral lipid, 12.0% glycolipid, and 59.7% phospholipid. The major lipids were again triglycerides for neutral lipids, mono- and diglycosyldiglycerides for glycolipids, and phosphatidyl choline and phosphatidylethanolamine for phospholipids.     

Whole-cell and membrane lipids of the methylotrophic bacterium Methylosinus trichosporium.

The lipid composition of the methylotrophic bacterium Methylosinus trichosporium was examined. Whole-cell lipid distribution was 39.1% neutral lipids, 34.5% polar lipids, and 26.4% poly-beta-hydroxybutyric acid. Membrane lipids were 83% phospholipids, with phosphatidylethanolamine and phosphatidylglycerol accounting for over 94% of the total. All the phospholipids had similar fatty acid compositions, with 18:1 accounting for about 87% of the total and most of the rest consisting of 16:1. Similarities between the lipid composition of this bacterium and other bacteria are discussed.