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PubMed1985

Growth of Acinetobacter sp. strain HO1-N on n-hexadecanol: physiological and ultrastructural characteristics.

The growth of Acinetobacter sp. strain HO1-N on hexadecanol results in the formation of intracytoplasmic membranes and intracellular rectangular inclusions containing one of the end products of hexadecanol metabolism, hexadecyl palmitate. The intracellular inclusions were purified and characterized as "wax ester inclusions" consisting of 85.6% hexadecyl palmitate, 4.8% hexadecanol, and 9.6% phospholipid, with a phospholipid-to-protein ratio of 0.42 mumol of lipid phosphate per mg of inclusion protein. The cellular lipids consisted of 69.8% hexadecyl palmitate, 22.8% phospholipid, 1.9% triglyceride, 4.7% mono- and diglyceride, 0.1% free fatty acid, and 0.8% hexadecanol, as compared with 98% hexadecyl palmitate and 1.9% triglyceride, which comprised the extracellular lipids. Cell-associated hexadecanol represented 0.05% of the exogenously supplied hexadecanol, with hexadecyl palmitate accounting for 14.7% of the total cellular dry weight. Acinetobacter sp. strain HO1-N possesses a mechanism for the intracellular packaging of hexadecyl palmitate in wax ester inclusions, which differ in structure and chemical composition from "hydrocarbon inclusions" isolated from hexadecane-grown cells.

Acinetobacter↗
PubMed1989

Purification and properties of a 28-kilodalton hemolytic and mosquitocidal protein toxin of Bacillus thuringiensis subsp. darmstadiensis 73-E10-2.

The mosquitocidal crystal of Bacillus thuringiensis subsp. darmstadiensis 73-E10-2 was purified, bioassayed against third-instar Aedes aegypti larvae (50% lethal concentration, 7.5 micrograms/ml), and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, revealing polypeptides of 125, 50, 47, and 28 kilodaltons (kDa). When solubilized and proteolytically activated by insect gut proteases or proteinase K, the crystal was cytotoxic to insect and mammalian cells in vitro and was hemolytic. By using nondenaturing polyacrylamide gel electrophoresis, a polypeptide of 23 kDa, derived from the 28-kDa protoxin, was identified which was hemolytic and cytotoxic to Aedes albopictus, A. aegypti, and Choristoneura fumiferana CF1 insect cell lines. The 23-kDa polypeptide was purified by ion-exchange chromatography and gave 50% lethal dose values of 3.8, 3.3, and 6.9 micrograms/ml against A. albopictus, A. aegypti, and C. fumiferana CF1 cells lines, respectively. Cytotoxicity in vitro was both dose and temperature dependent, with a sigmoidal dose-response curve. The cytotoxicity of the 23-kDa toxin and the solubilized and proteolytically activated delta-endotoxin was inhibited by a range of phospholipids containing unsaturated fatty acids and by triglyceride and diglyceride dispersions. An interaction with membrane phospholipids appears important for toxicity. Polyclonal antisera prepared against the 23-kDa polypeptide did not cross-react with polypeptides in the native crystals of four other mosquitocidal strains.

Animals↗
PubMed1963

FATTY ACID COMPOSITION OF LIPIDS FROM STREPTOCOCCUS CREMORIS AND STREPTOCOCCUS LACTIS VAR. MALTIGENES.

MacLeod, Patricia (University of Connecticut, Storrs) and Joseph P. Brown. Fatty acid composition of lipids from Streptococcus cremoris and Streptococcus lactis var. maltigenes. J. Bacteriol. 85:1056-1060. 1963.-A method for the extraction of lipids from bacterial cells, involving grinding in a ball mill, is described. Cells of Streptococcus lactis var. maltigenes and S. cremoris yielded 5.3 and 5.5%, respectively, of their dry cellular weights as lipid. The lipids of both organisms were separated into three fractions by thin-layer chromatography. Two of these fractions have been classified: one fraction containing phospho- and perhaps glycolipids and the other containing triglycerides. The unidentified fraction was probably either mono- or diglyceride in nature. The fatty acid composition of the total lipid as well as that of each of the separated lipid components from the two lactic strains were compared.

Chemical Phenomena↗
PubMed1967

Phospholipids and glycolipids of sterol-requiring Mycoplasma.

The phospholipids of Mycoplasma hominis type 2 strain 07 are composed almost entirely of phosphatidyl glycerol. Traces of other glycerophospholipids may exist. No glycolipids are found. The phospholipids of Mycoplasma sp. avian strain J are composed of diphosphatidyl glycerol, which predominates in older cultures, a monoacyl glycerophosphoryl glycerophosphate, which may serve as a precursor of diphosphatidyl glycerol, and phosphatidyl glycerophosphate. This organism also contains cholesteryl glucoside and an unidentified glycolipid which appears to be similar to a monoglucosyl diglyceride. No turnover or radioisotope labeling of the phospholipids occurs during metabolism. This lack of turnover during growth is indicative of a structural role for these glycerophospholipids. A concomitant decrease of monoacyl glycerophosphoryl glycerophosphate and increase of diphosphatidyl glycerol occurs during growth.

Fatty Acids↗
PubMed1967

Membrane lipid changes during formation of a functional electron transport system in Staphylococcus aureus.

Addition of oxygen to a culture of anaerobically growing Staphylococcus aureus results in the formation of a membrane-bound, functional electron transport system. With the shift to aerobic growth, there is at least a 15-fold increase in cytochrome a and at least a 55-fold increase in cytochrome oxidase o. At the completion of the shift to aerobic growth, the cytochrome levels equal those found in bacteria grown with aeration throughout the entire growth cycle. Cytochromes b(1) and o are formed first. Their synthesis slows when cytochrome a becomes detectable. Concentrations of cytochromes b(1) and sometimes cytochrome a increase late in the adaptive period. Concomitant with this is a decrease in the oxygen tension at which the rate of oxygen utilization becomes dependent on the oxygen concentration. During the shift to aerobic growth, the protoheme content increases ninefold, and all the protoheme can be accounted for in enzymatically reducible cytochrome b(1) and cytochrome oxidase o. Protoheme, but not a functional cytochrome system, is synthesized by anaerobically growing S. aureus. Heme a appears only after a period of aerobic growth. During the shift to aerobic growth, there is a 1.6-fold increase in the vitamin K(2) content, with an alteration in the ratios of the 35 and 45 carbon side chain isoprenologues. A twofold increase in phosphatidyl glycerol and a 1.6-fold increase in cardiolipin occur with the shift to aerobic growth. Lysyl-phosphtidyl glycerol remains essentially constant in this period. Concentrations of mono- and diglucosyl diglycerides increase coordinately 1.3-fold during the shift to aerobic growth at a 2.5 to 1 m ratio.

Cell Membrane↗
PubMed1969

Phospholipid metabolism during changes in the proportions of membrane-bound respiratory pigments in Haemophilus parainfluenzae.

After a transition from high to low oxygen tension, there was a twofold to 50-fold increase in the content of membrane-bound respiratory pigments of Haemophilus parainfluenzae, and there were concurrent changes in the metabolism of the membrane phospholipids: (i) a twofold decrease in the rate of turnover of the phosphate in all the phospholipids; (ii) a shift from simple one-phase, linear incorporation of phosphate into phospholipids to a complex biphasic incorporation of phosphate into phospholipids; and (iii) an increase in the total phospholipids with a slight increase in the proportion of phosphatidylglycerol (PG) and a slight decrease in the proportion of phosphatidylethanolamine (PE). Changes in the rates of incorporation of phosphate into the phospholipids occurred without a change in the rate of bacterial growth. When the compensatory adjustment of the proportions of the respiratory pigments reached a steady state, the total phospholipid, the rate of incorporation of phosphate into phospholipids, and the proportion of PG fell. At steady-state proportions of cytochromes, the proportion of PE and the rate of turnover of the phosphate in the phospholipids increased. All through an incorporation experiment of 1.5 divisions, the specific activity of the phosphate of PG was twice that of phosphatidic acid (PA). The phosphate of PG turned over 1.2 to 1.5 times more rapidly than the phosphate of PA in cells with high and low cytochrome levels. If the PA was an accurate measure of the precursor for the cytidine-5'-diphosphate-diglyceride, which in turn was the precursor of all the lipids, then the results of these experiments suggested that exchange reactions, in addition to synthesis from PA, were involved in phospholipid metabolism. These reactions were more sensitive to changes in oxygen concentration than was the growth rate.

Amino Alcohols↗
PubMed2001

Detection of phospholipase C in nontuberculous mycobacteria and its possible role in hemolytic activity.

Phospholipase C plays a key role in the pathogenesis of several bacterial infections, for example, those caused by Clostridium perfringens and Listeria monocytogenes. Previous studies have reported multiple copies of plc genes homologous to Pseudomonas aeruginosa plcH and plcN genes encoding the hemolytic and nonhemolytic phospholipase C enzymes in the genomes of Mycobacterium tuberculosis, M. marinum, M. bovis, and M. ulcerans. In this study we analyzed the possible relationship between phospholipase C and hemolytic activity in 21 strains of nontuberculous mycobacteria representing nine different species. Detection of phospholipase C enzymatic activity was carried out using thin-layer chromatography to detect diglycerides in the hydrolysates of radiolabeled phosphatidylcholine. DNA sequences of M. kansasii and M. marinum homologous to the genes encoding phospholipase C from M. tuberculosis and M. ulcerans were identified by DNA-DNA hybridization and sequencing. Finally, we developed a direct and simple assay to detect mycobacterial hemolytic activity. This assay is based on a modified blood agar medium that allows the growth and expression of hemolysis of slow-growing mycobacteria. Hemolytic activity was detected in M. avium, M. intracellulare, M. ulcerans, M. marinum, M. tuberculosis, and M. kansasii mycobacteria with phospholipase C activity, but not in M. fortuitum. No hemolytic activity was detected in M. smegmatis, M. gordonae, and M. vaccae. Whether or not phospholipase C enzyme plays a role in the pathogenesis of nontuberculous mycobacterial diseases needs further investigation.

Culture Media↗
PubMed1994

Activation of Ras in vitro and in intact fibroblasts by the Vav guanine nucleotide exchange protein.

We recently identified Vav, the product of the vav proto-oncogene, as a guanine nucleotide exchange factor (GEF) for Ras. Vav is enzymatically activated by lymphocyte antigen receptor-coupled protein tyrosine kinases or independently by diglycerides. To further evaluate the physiological role of Vav, we assessed its GDP-GTP exchange activity against several Ras-related proteins in vitro and determined whether Vav activation in transfected NIH 3T3 fibroblasts correlates with the activity status of Ras and mitogen-activated protein (MAP) kinases. In vitro translated purified Vav activated by phorbol myristate acetate (PMA) or phosphorylation with recombinant p56lck displayed GEF activity against Ras but not against recombinant RacI, RacII, Ral, or RhoA proteins. Expression of vav or proto-vav in stably transfected NIH 3T3 cells led to a approximately 10-fold increase in basal or PMA-stimulated Ras exchange activity, respectively, in total-cell lysates and Vav immunoprecipitates. Elevated GEF activity was paralleled in each case by a significant increase in the proportion of active, GTP-bound Ras. PMA had a minimal effect on the low Ras. GTP level in untransfected control fibroblasts but increased it from 20 to 37% in proto-vav-transfected cells. vav-transfected cells displayed a constitutively elevated Ras. GTP level (35%), which was not increased further by PMA treatment. MAP kinases, known downstream intermediates in Ras-dependent signaling pathways, similarly exhibited increased basal or PMA-stimulated activity in Vav-expressing cells by comparison with normal NIH 3T3 cells. These results demonstrate a physiologic interaction between Vav and its target, Ras, leading to MAP kinase activation.

3T3 Cells↗
PubMed1964

THE IMPURITY OF RADIOIODINATED TRIOLEIN.

Commercially supplied radioiodinated triolein has been shown by thin-layer chromatography and silicic acid column chromatography to contain impurities, consisting mainly of diglycerides and monoglycerides, but also a small amount of free fatty acid. The effect of these impurities on the radioiodinated triolein absorption test requires further investigation.

Autoradiography↗
PubMed1975

The lipids of four unusual non-pathogenic host-associated spirochetes.

The lipid compositions of two spirochetes isolated from the human oral cavity and two isolated from pig feces were examined. These isolates were unusual in that they did not require long-chain fatty acids for growth, as do the other host-associated spirochetes, but rather required isobutyric and valeric acids. Therefore, they could be cultured in a medium free of serum or fatty acid - albumin supplements. The major fatty acids synthesized were normal and iso fatty acids with 14 and 16 carbons. No unsaturated fatty acids were detected, nor were chain lengths longer than 16 carbons. The major complex lipids found were monogalactosyl diglyceride, phosphatidyl glycerol, and bis-phosphatidyl glycerol. Nitrogenous phospholipids, present in Treponema and Leptospira, were not synthesized by these novel strains. The data indicate an intermediate position of these isolates between Treponema and free-living Spriochaeta.

Animals↗
PubMed1983

Effect of triglycerides on the production of lipids and lipase by Mucor hiemalis.

The effect of triglycerides on the growth of Mucor hiemalis and the production of lipase and mycelial lipids was studied. Addition of 1% triglycerides to the fermentation medium was best for the mycelial as well as the broth lipase production. The added triglycerides seemed to be utilized through the formation of free fatty acids, and towards the end of the growth phase most of the triglycerides and their hydrolysis products were utilized. The mycelial lipase activity was maximum (66 U/g dry mycelium) at the end of the growth phase, while the maximal broth lipase activity (204 U/100 mL) was achieved after the cell lysis had started. The lipids produced per gram mycelia were high initially (260 mg/g dry weight at 48 h), reducing gradually later. With increase in growth the maximum mycelial lipids per 100 mL of culture medium was obtained after 96 h (176 mg/100 mL). The various fractions detected in the mycelial lipid extracts were sterol esters, triglycerides, free fatty acids, diglycerides, sterols, monoglycerides, phosphatidyl ethanolamine, phosphatidyl choline, and small amounts of an unknown polar lipid at all the stages of fermentation studied. Proportion between total neutral and total polar lipids remained nearly constant throughout fermentation.

Dose-Response Relationship, Drug↗
PubMed1978

Selective degradation with phospholipases D and C of radioactive isomeric spin-labelled lipids bound to guinea pig liver microsomal membranes.

Membrane-bound lipids of isolated guinea pig liver microsomal membranes were selectively enzymatically labelled with isomeric (5-, 12-, and 16-)doxyl stearic acid. After reisolation, the membranes were degraded with phospholipases D and C under conditions not requiring detergents or organic solvent activators. The degradation of membrane-bound lipids occurred according to the recognized specificity of phospholipases D and C. Temperature-induced changes of degraded membranes containing radioactive spin-labelled isomeric lipids were followed by the electron spin resonance and spectral changes correlated with the lipid composition of membranes. Discontinuities in plots of experimental spectral parameters versus temperature detected in the case of microsomal membranes before and after degradation with phospholipases D and C were attributed to lipid-protein and lipid-lipid interaction(s). On the basis of these and control experiments, discontinuity at around 10-12 degrees C was attributed to the microsomal membrane phosphatidylcholine intrinsic microsomal membrane protein interaction(s), while discontinuities detected at 19-21 degrees C approximately and at 20-30 degrees C approximately were attributed to the phase separation of Ca or Zn salts of membranous phosphatidic acid and to the similar phenomenon involving membrane-bound diglycerides respectively.

Animals↗
PubMed1978

The viscosity and lipid composition of the plasma membrane of multiple drug resistant and sensitive yeast strains.

Four different plasma membrane preparations were isolated from multiple drug resistant and sensitive isolates of two isogenic groups of Saccharomyces cerevisiae strains: zymolyase ghosts, concanavalin A ghosts, pH 4 nonaggregated vesicles, and sucrose-gradient purified vesicles. The viscosities of these preparations were determined by the use of a fluorescence polarization technique with 1,6-diphenyl-1,3,5-hexatriene. The viscosities of all four membrane preparations within an isogenic set were the same for resistant and sensitive strains. A comparison of the viscosity of zymolyase ghost liposomes showed that zymolyase ghost (glyco) proteins of resistant and sensitive strains had the same effect on viscosity. There was no difference between resistant and sensitive isolates in the mole concentration of the following lipid classes extracted from zymolyase ghosts: phospholipid, sterol, sterol ester, triglyceride, diglyceride, and free fatty acid. The fatty acid distribution of esterified and free fatty acids and the distribution of nine phospholipids was the same in zymolyase ghosts from sensitive and resistant strains. It was concluded that multiple drug resistance does not result from an alteration in plasma membrane viscosity or lipid composition.

Cell Membrane↗
PubMed1980

Mitochondrial importation of lipids and liponucleotides from microsomes independent of and facilitated by purified cytosol proteins.

The mitochondrial importation of microsomal lipids and liponucleotides in the presence and in the absence of partially purified cytosol protein(s) isolated from guinea pig liver was studied by the aid of isomeric (5-, 12-, and 16-(N-oxyl-4',4'-dimethyloxazolidine)stearoyl) spin-labelled radioactive phosphatide acid, phosphatidylcholine, neutral lipids, and CDP-diglycerides. Using a conventional procedure for the protein purification, cytosol protein(s) was purified approximately 1000-fold in respect to its ability to catalyze the translocation of isomeric spin-labelled lipids and liponucleotides from the microsomal to mitochondrial membranes. The highest activity of this protein was exhibited with biosynthesized spin-labelled lipids and liponucleotides bound to the microsomal membranes as substrates and the lowest, with the synthetic liponucleotides and derived lipids bound to the microsomal membranes. The partially purified protein was active in catalyzing the mitochondrial import of phospholipids from microsomes after heat treatment up to 90 degrees C. In addition to the cytosol protein catalyzing mechanism of mitochondrial import of lipids and liponucleotides from microsomal membranes, another cytosol protein independent mechanism of the mitochondrial importation of the same lipids and liponucleotides was also demonstrated in an agreement with our previous reports on the existence of cytosol protein independent intermembranous translocation of phospholipids. These experimental findings are discussed in terms of possible physiological significance and reaction mechanisms involved in the mitochondrial import of lipids and liponucleotides from the microsomal membranes of guinea pig liver.

Animals↗
PubMed1982

Interaction of lipids with intestinal brush border membrane preparations.

Conditions for uptake of lipids by rabbit intestinal brush border membrane preparations were investigated. A variety of lipids were found to be incorporated, including choline and ethanolamine phosphatides as well as cholesterol, diglyceride, and fatty acid. The incorporation of those lipids tested was enhanced by Ca2+ and other divalent cations but not by monovalent cations. The optimal Ca2+ concentration was approximately 10 mM. The uptake varied with lipid and membrane protein concentration and proceeded at rates which were too rapid to measure under several assay conditions tried. Incorporations were decreased substantially outside the pH range of 6.5-8.0. The effect of one lipid, phosphatidylcholine, on the structural appearance of the membrane fraction was examined by electron microscopy. No free or surface-bound lipid structures could be detected and the membrane fractions appeared to be unchanged after uptake.

Animals↗
PubMed1982

Studies on the uptake of exogenous phosphoglycerides by Escherichia coli B cells.

The uptake of exogenous lipids by Escherichia coli B was studied under various conditions. Lysophosphoglycerides were absorbed more readily than diacyl analogues when sonicated dispersions of a single lipid were used. When these same lipids were admixed with coliform lipids and dispersed as vesicles, the uptake of lysophosphoglyceride diminished and was approximately equal to that of diacyl analogues. Neutral lipids such as diglyceride, fatty acid, and cholesterol were also absorbed when admixed and dispersed as vesicles with coliform lipids. The uptake of lysophosphoglyceride was stimulated slightly by all divalent cations tested except Mg2+; monovalent cations were ineffective. Uptake was accompanied by conversion of lysophosphoglyceride to diacyl analogues. In the presence of Ca2+, lysophosphatidylethanolamine also formed a more polar lipid product yet unidentified. The uptake of lipid did not cause release of 3H label into the medium from cells that had been grown in [3H]acetate-containing medium. Also, the [3H]phosphoglyceride content of such labelled cells remained constant. Thus the uptake process did not involve exchange of membrane lipid with the medium or an enhanced hydrolysis of endogenous lipids, but it represented a net gain of lipid by the cell. The uptake did not seem to involve a stable adsorption of lipid at the surface of the cell as could be judged from electron microscopic examination of the cells after incubation; the cell surfaces were devoid of adsorbed vesicle or liposomal types of structures and did not display evidence of expansion. [3H]Cholesterol-[32P]phospholipid mixtures were taken up without a change in isotopic ratio. This result together with the other evidence presented indicate a net uptake of exogenous lipid by a process likely involving fusion.

Acetates↗
PubMed1986

Origins of the phospholipids in animal mitochondria.

As is the case for the assembly of protein components of the membranes in animal mitochondria, the bilayer phospholipids arise from a complicated interplay of intra- and extra-mitochondrial reactions. Our early studies indicated that the bulk of mitochondrial phospholipids (typified by phosphatidylcholine) had their origin in the endoplasmic reticulum and were transported to the mitochondria as complexes with phospholipid-exchange proteins. The polyglycerophosphatides (typified by diphosphatidylglycerol) were apparently synthesized in situ by intramitochondrial membrane-bound enzymes using CDP-diglycerides as intermediates. The case for the precursors in the latter pathway is less clear, although evidence has been presented for dual localization of enzymes for glycerophosphate acylation and CTP:phosphatidate cytidylyl transfer in both mitochondria and microsomes. Phosphatidylethanolamine also shows evidence for two sites of origin: by translocation from its site of synthesis in the endoplasmic reticulum and by translocation of phosphatidylserine followed by decarboxylation within the mitochondria. In the latter case mitochondrial phosphatidylserine decarboxylase may play an important role in the regulation of phospholipid metabolism throughout the cell.

Animals↗
PubMed1992

Use of [1-14C]oleate labelled autoclaved Escherichia coli as a membranous substrate for measurement of in vitro phospholipase D activity.

Autoclaved Escherichia coli labelled with [1-14C]oleate in the 2-acyl position have been used extensively to measure phospholipase A2 activity in vitro. The present study demonstrates that this membranous substrate is also useful for the measurement of in vitro phospholipase D activity. Phospholipase D from Streptomyces chromofuscus catalyzed the hydrolysis of [1-14C]oleate labelled, autoclaved E. coli optimally at pH 7.0-8.0 to generate [14C]phosphatidic acid in the presence of 5 mM added Ca2+. Other divalent cations would not substitute for Ca2+. Activity was linear with time and protein up to 30% of the hydrolysis of substrate. Phospholipase D activity was stimulated in a dose-dependent manner by the addition of Triton X-100. The activity was increased 5.5-fold with 0.05% Triton, a concentration that totally inhibited hydrolysis of E. coli by human synovial fluid phospholipase A2. Accumulation of [14C]diglyceride was observed after 10 min of incubation. This accumulation was inhibited by NaF (IC50 = 18 microM) or propanolol (IC50 = 180 microM) suggesting the S. chromofuscus phospholipase D was contaminated with phosphatidate phosphohydrolase. Phosphatidic acid released by the action of cabbage phospholipase D was converted to phosphatidylethanol in an ethanol concentration dependent manner. These results demonstrate that [1-14C]oleate labelled, autoclaved E. coli can be used to measure phospholipase D activity by monitoring accumulation of either [14C]phosphatidic acid or [14C]phosphatidylethanol.

Brassica↗