Lipid profiles of conidia of Aspergillus niger and a fatty acid auxotroph

Conidial lipids of the wild-type (V35) Aspergillus niger and its unsaturated fatty acid auxotroph (UFA2) were compared. The wild type contained lower levels (7.6%) of phospholipids and higher levels (28.4%) of glycolipids than the mutant (16.5 and 22.2%, respectively). Oleic (33.4%), linoleic (22.5%), palmitic (12.8%), stearic (7.4%), and linolenic (6.2%) were the main fatty acids of the wild type (V35). The mutant grew only in the presence of unsaturated fatty acid having at least one delta 9cis double bond, and its conidial fatty acid profile was influenced by the exogenous acid. Analyses of the fatty acids of UFA2 grown in the presence of different fatty acid supplements support the original view that the mutant is defective in delta 9-desaturase activity.     

An unsaturated fatty acid mutant of Aspergillus niger with partially defective delta 9-desaturase

The wild-type Aspergillus niger (V35) does not require fatty acids for growth. Four unsaturated fatty acid auxotrophs designated as UFA1, UFA2, UFA3, and UFA4 have been produced from this organism by treating the conidia of the wild-type strain with a mutagen, N-methyl-N'-nitro-N-nitrosoguanidine, followed by isolation on media containing monounsaturated fatty acids and the nonionic detergent, Brij 58. Optimal growth of the mutants comparable with that of the wild type was achieved with medium supplemented with C16 or C18 unsaturated fatty acids containing at least one cis double bond at the delta 9 position. Some other fatty acids (18:1 delta 11 cis and 16:1 delta 9 trans) support growth to some extent. The mutants do not grow at all in the presence of saturated fatty acids. Fatty acid analyses of the mutant, UFA2, grown in the presence of different fatty acid supplements reveal that it may be defective in a desaturase system. Experiments with unlabeled and [1-14C]palmitoyl-CoA have shown that the microsomes of the mutant (UFA2) contain a partially defective delta 9-desaturase system.     

Effect of sterol side chains on growth and membrane fatty acid composition of Saccharomyces cerevisiae.

Saccharomyces cerevisiae GL7 cells require exogenous sterol and unsaturated fatty acid for growth. When grown in the presence of cholesterol or 7-dehydrocholesterol, the cells incorporated less saturated fatty acid into phospholipids than cells grown with ergosterol, stigmasterol, or beta-sitosterol as the sterol source. This lower saturated fatty acid content was most pronounced in phosphatidylethanolamine, slightly less so in phosphatidylcholine, and least evident in phosphatidylserine and phosphatidylinositol. Growing the cells with the various sterols did not affect the ratios of individual phospholipids. The ability of strain GL7 to use 7-dehydrocholesterol as the only sterol supplement for growth was dependent upon the nature of the unsaturated fatty acids added to the growth medium. In the presence of linoleic, linolenic, or a mixture of palmitoleic and oleic acids, excellent growth was observed with either ergosterol, cholesterol, or 7-dehydrocholesterol. However, when the medium was supplemented with either oleic or petroselenic acid, the cells grew more slowly (oleic) or much more poorly (petroselenic) with 7-dehydrocholesterol than with ergosterol. A specific relationship between sterol structure and membrane fatty acid composition in yeast cells is implied.     

The influence of fatty acids on model cholesterol/phospholipid membranes

The aim of this work was to verify the influence of the saturated (SFA) (stearic acid) and the unsaturated (UFA) (oleic and alpha-linolenic) fatty acids on model cholesterol/phospholipid membranes. The experiments were based on the Langmuir monolayer technique. Cholesterol and phospholipid were mixed in the molar ratio that corresponds to the proportion of these lipids in the majority of natural human membranes. Into the binary cholesterol/phospholipid monolayers, various amounts of fatty acids were incorporated. Our investigations were based on the analysis of the interactions between molecules in ternary (cholesterol/phospholipids/fatty acid) mixtures, however, also binary (cholesterol/fatty acid and phospholipids/fatty acid) mixed system were examined. It was concluded that the influence of the fatty acids on model cholesterol/phospholipid membrane is closely connected with the shape of the fatty acid molecule, resulting from the saturation degree of the hydrocarbon chain. It was found that the saturated fatty acid makes the model membrane more rigid, while the presence of unsaturated fatty acid increases its fluidity. The increasing amount of stearic acid gradually destabilizes model membrane, however, this effect is the weakest at low content of SFA in the mixed monolayer. Unsaturated fatty acids in a small proportion make the membrane thermodynamically more stable, while higher content of UFA decreases membrane stability. This explains low proportion of the free fatty acids to other lipids in natural membrane.     

Phospholipids and fatty acids of Neisseria gonorrhoeae.

The phospholipids and fatty acids of two strains of Neisseria gonorrhoeae of different penicillin susceptibilities were examined. The phospholipids, which comprise about 8% of the dry weight of the cells, consisted of phosphatidylethanolamine (70%) and phosphatidylglycerol (20%); small amounts of phosphatidylcholine and traces of cardiolipin were also present. Growing and stationary-phase cells were similar in content and composition of phospholipids except for phosphatidylcholine, which increased two- to fivefold in the stationary-phase cells. The fatty acids of the phospholipids were characterized by two major acids, palmitic and a C16:1, with myristic and a C18:1 acid present in smaller amounts. The fatty acids present in purified phospholipid fractions varied considerably in relative proportions from fraction to fraction. No significant difference in the composition of phospholipids from the two strains was evident. Large amounts of beta-hydroxy lauric acid were detected only after saponification of the organisms. Differences in the lipid composition between the gonococcus and other gram-negative bacteria are discussed.     

Lipid composition of aminopterin-resistant and sensitive strains of Streptococcus pneumoniae. Effect of aminopterin inhibition.

The polar lipids of Streptococcus pneumoniae wild type and aminopterin-resistant strains were analysed. The membrane contained only two acid phospholipids, phosphatidylglycerol and cardiolipin, and a large amount of two glycolipids, glucosyldiglyceride and galactosylglucosyldiglyceride. The unsaturated acyl chains ranged from 58 to 87% of total fatty acids, depending on the strain and on growth conditions. No relation could be established between aminopterin resistance and polar lipid or fatty acid compositions. However, in the presence of bacteriostatic concentrations of aminopterin, the wild type and the resistant mutant did not have the same behavior. The resistant strain maintained its fatty acid composition and a normal [32P]phosphate distribution among phospholipids while the wild type shifted to a higher content in unsaturated fatty acids and to a high relative cardiolipin labelling. Such a differencein [32P] distribution was not observed when bacteriostatic concentrations of chloramphenicol were used, or when growth was stopped after amino acid deprivation induced by high concentrations of isoleucine. The biochemical basis of the aminopterin resistant character of the amiA mutants are not yet well understood but the present study establishes that the mutation confers a certain insensitivity of the lipid metabolism to aminopterin.     

The lipid composition and permeability to the triazole antifungal antibiotic ICI 153066 of serum-grown mycelial cultures of Candida albicans

The total lipid content of Candida albicans (serotype A: NCPF 3153) exponential-phase mycelial cultures grown in tissue-culture medium 199 (containing 10%, v/v, foetal calf serum) was 29.8 +/- 8 mg (g dry weight)-1 (mean +/- SD). The weight ratios of phospholipid to neutral lipid and phospholipid to non-esterified sterol were 2.6 +/- 0.4 and 24.9 +/- 0.5, respectively. The major phospholipid was phosphatidylcholine with smaller amounts of phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylglycerol and diphosphatidylglycerol; the most abundant fatty acids were palmitic, palmitoleic, oleic and linoleic acids. The major neutral lipids comprised esterified sterol, triacylglycerol and non-esterified fatty acid with a smaller amount of non-esterified sterol. The fatty acid compositions of the three fatty-acid-containing neutral lipids were distinct from each other and the phospholipids. Comparison with previous data on yeast cultures of C. albicans A grown in glucose broth shows that mycelial cultures have a larger lipid content, lower phospholipid to neutral lipid ratio and higher phospholipid to non-esterified sterol ratio. We now show that mycelial cultures were more permeable to a [14C]triazole antifungal antibiotic compared with exponentially growing yeast cultures of several azole-sensitive strains. Taken together these data are consistent with there being a relationship between the phospholipid/non-esterified sterol ratio of a culture and its ability to accumulate a triazole.     

Isolation and characterization of glycolipids from some photosynthetic bacteria

Glycosyl glycerides have been found in substantial amounts in Chloropseudomonas ethylicum but could not be detected in two strains of Rhodopseudomonas palustris. Rhodospirillum molischianum possibly contains small amounts of monoglycosyl diglyceride. The glycolipids of C. ethylicum have been separated into two components. One of these, glycolipid I, is a monogalactosyl diglyceride. Glycolipid II, upon acid hydrolysis, yields galactose, rhamnose, and a third, unidentified sugar. The glycolipids or total lipids of the photosynthetic bacteria examined contained saturated and monounsaturated, but none of the more highly unsaturated, fatty acids.     

Lipid composition of plasma membranes isolated from sunflower seedlings grown under water-stress

Plasma membranes were isolated by aqueous two-phase-partitioning from sunflower ( Helianthus annuus cv. Isabel) seedlings grown both under field irrigation and dryland conditions. Water-stressed plants showed a decrease in the leaf water potential and in the osmotic potential at full turgor, with the turgor pressure remaining at positive values. Dryland conditions also induced a reduction in the bulk modulus of elasticity. Plasma membranes of irrigated plants were characterized by high contents of phospholipids (68% of total lipids), free sterols (15. 7%) and glycolipids (9. 1%), mainly glycosphingolipids and steryl glycosides. Diacylglycerols, triacylglycerols and free fatty acids were also present. The major phospholipids were phosphatidylcholine and phosphatidylethanolamine with smaller amounts of phosphatidylinositol and phosphatidylglycerol. Following water stress, the plasma membranes showed a reduction of about 24 and 31% in total lipids and phospholipids, respectively. Also the amounts of glycolipids and diacylglycerols decreased significantly upon water stress. There was no change in free fatty acids, however, and triacylglycerols and free sterols increased. As a consequence, the free sterol to phospholipid molar ratio increased from 0. 4 to 0. 7 under water deficit conditions. The ratio of phosphatidylcholine to phosphatidylethanolamine increased from 1. 1 (control plants) to 1. 6 (water-stressed plants), while phosphatidic acid rose to 4% of total phospholipids. Dehydration did not result in any substantial change in the unsaturation level of the individual lipid classes, however. The results show that dryland conditions resulted in a marked alteration in the lipid composition of the sunflower leaf plasma membrane     

Variable recoveries of fatty acids following the separation of lipids on commercial silica gel TLC plates Selective loss of unsaturated fatty acids on certain brands of plates

Since we recently noticed poor recoveries of unsaturated fatty acids (UFA) when the parent lipids were first separated on TLC plates, we investigated the source of this error by examining several variables, including the brand of TLC plate, nature of the lipid, and conditions of methylation. Of the five commercial brands of plates used, two (Baker and Whatman) showed loss of UFA, and three (Alltech Hardlayer, Alltech Softlayer, and Merck) did not. This loss occurred in both neutral and phospholipids, did not affect saturated acids, and was independent of the methylation reagent used. No loss occurred, however, if the lipids were eluted from the silica gel before methylation, indicating that the loss is due to oxidation of UFA in presence of certain brands of silica gel. These results show that some brands of TLC plates may be unsuitable for lipid analysis, if the aim is to determine the fatty acid composition by GC using direct methylation.     

The lipid composition of Acer pseudoplatanus cells grown in culture

Cells of Acer pseudoplatanus were grown in batch suspension culture for 22 days. The cultures were initiated at high cell density of 2 × 10⁵ cells per ml of culture. Growth was characterised by a short lag phase, an exponential phase of rapid cell division and growth, and finally a stationary phase. Quantitative but not qualitative changes were observed in total lipid content, fatty acids and phospholipids at different stages of growth. Total lipids, phospholipids and fatty acids showed maximum concentrations in 12 day old cells. The major phospholipids isolated were phosphatidylcholine and phosphatidylethanolamine with minor amounts of phosphatidic acid and lysophosphatides. Other lipid components present were mono- and digalactosyl diglycerides, cerebrosides, sterol glucosides, free fatty acids and esterified sterol glucosides. The major constituent fatty acids were myristic acid (14:0), palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2) and linolenic acid (18:3). During exponential cell growth the proportion of 16:0, 18:2 and 18:3 constituted nearly 90% of the total fatty acids. Triglycerides were the major repository of myristic acid (14:0) with substantial amounts of palmitic acid (16:0), whereas phospholipids contained 16:0, 18:2 and 18:3 in high amounts.     

Effects of saturated and unsaturated fats given with and without dietary cholesterol on hepatic cholesterol synthesis and hepatic lipid metabolism

Hepatic cholesterol synthesis was studied in rats after consuming diets of varying neutral lipid and cholesterol content. Cholesterol synthesis was evaluated by measuring 3-hydroxy-3-methylglutaryl-CoA reductase and by determining the rate of 3H-labeled sterol production from [3H]mevalonate. Results were correlated with sterol balance data and hepatic lipid content. Hepatic cholesterol synthesis was relatively great when cholesterol was excluded from the diet. The source of neutral dietary lipids, saturated vs. unsaturated, produced no change in hepatic sterol synthesis. Values for fecal sterol outputs and hepatic cholesterol levels were also similar in rats consuming either saturated or unsaturated fats. When 1% cholesterol was added to the diet, hepatic cholesterol synthesis was suppressed but the degree of suppression was greater in rats consuming unsaturated vs. saturated fats. This was associated with greater accumulation of cholesterol in livers from rats consuming unsaturates and a reduction in fecal neutral sterol output in this group as opposed to results from rats on saturated fats. Cholesterol consumption also altered the fatty acid composition of hepatic phospholipids producing decreases in the percentages of essential polyunsaturated fatty acids. It is concluded that dietary cholesterol alters cholesterol and fatty acid metabolism in the liver and that this effect is enhanced by dietary unsaturated fats.     

Energy metabolism of sea urchin spermatozoa, with phosphatidylcholine as the preferred substrate

Phosphatidylcholine content in the spermatozoa of the sea urchin, Hemicentrotus pulcherrimus, decreased rapidly during incubation with sea water. Sea urchin sperm contained approx. 85% phospholipid in total lipid. Phosphatidylcholine (PC) was the principal lipid. Other phospholipids, however, remained at constant levels during incubation. Although the free fatty acid content gradually increased following dilution of dry sperm in sea water, the amounts of triacylglycerol and cholesterol ester were extremely low. Analysis by gas-liquid chromatography indicated most of fatty acid moieties in PC to be polyenoic. PC composed in part of unsaturated fatty acids was consumed to a greater extent during incubation than that consisting of saturated fatty acids. Furthermore, 1-palmitoyl-2-[1-14C]linoleoylphosphatidylcholine was transformed to 14C-labelled free fatty acid in a subcellular system. Thus, possibly, phospholipase A2 is present in sea urchin sperm. Also, [1-14C]oleic acid was immediately oxidized to 14CO2 by sperm. It is thus concluded that sea urchin sperm use phosphatidylcholine as a substrate for energy metabolism.     

Fatty chain composition of phospholipids in sea urchin spermatozoa

1. An analysis was made of lipids extracted from the spermatozoa of the sea urchins, Hemicentrotus pulcherrimus and Anthocidaris crassispina. 2. Nearly all the lipids from both species consisted of phospholipids (about 80%) and cholesterol (about 14%). Triglyceride and cholesterol ester were present in trace amounts. 3. The fatty acid composition of each phospholipid was determined by gas-liquid chromatography. In both species, the fatty acid consisting of phosphatidylethanolamine was of the unsaturated type for the most part, while cardiolipin was comprised to a considerable degree of saturated fatty acids. In phosphatidylcholine and phosphatidylserine from H. pulcherrimus sperm, unsaturated fatty acid content was somewhat higher than that in phospholipids from A. crassispina sperm.     

Lipid biosynthesis in the marine flatworm Convoluta roscoffensis and its algal symbiont Platymonas convoluta.

As a part of an investigations on the lipid metabolism in Platyhelminthes, the acoel Convoluta roscoffensis, which harbors the green alga Platymonas convoluta as a symbiont, was studied. Isotopic tracer experiments established that the acoel lacks the ability to synthesize de novo long-chain saturated and unsaturated fatty acids and depends on its algal symbiont for these compounds. The acoel's fatty acid composition closely resembles that of the alga but differs from those of other animals; the acoel's polyunsaturated fatty acids are of the plant type (omega 3 family) rather than of the animal type (omega 6 family). The acoel also lacks the ability to synthesize sterols de novo. It contains 24-methylenecholesterol synthesized by the algae and, in addition, significant amounts of cholesterol, which is probably a host modification product of the algal sterol. With fatty acids provided by the symbiont, the acoel has the ability to synthesize its own complex lipids. The acoel contains relatively large amounts of triglyceride, phosphatidylcholine, and ethanolamine plasmalogen. These compounds are either not present at all or present only in minute amounts in the symbiotic alga. Since acoels belong to the most primitive forms of the present-day flatworms, the observed metabolic defects in this organism suggest that mechanisms for the biosynthesis of fatty acids and sterols were lost early during the evolution of the Platyhelminthes, and that this phenomenon is widespread within the phylum.     

Mechanism of ethanol-induced changes in lipid composition of Escherichia coli: inhibition of saturated fatty acid synthesis in vivo.

The in vivo effects of ethanol on lipid synthesis in Escherichia coli have been examined. Under conditions which uncoupled fatty acid synthesis from phospholipid synthesis, ethanol decreased the amount of saturated fatty acids synthesized but had little effect on the selectivity of their incorporation into phospholipids. In the absence of fatty acid degradation and unsaturated fatty acid synthesis, E. coli was still able to adapt its membrane lipids to ethanol, while the inhibition of total fatty acid synthesis eliminated this response. During growth in the presence of ethanol, strain K1060 (an unsaturated fatty acid auxotroph) incorporated an increased amount of exogenous heptadecanoic acid (17:0) to compensate for the reduction in palmitic acid (16:0) available from biosynthesis. Thus, our results indicate that the reduced levels of saturated fatty acids observed in the phospholipids of E. coli following growth in the presence of ethanol result primarily from a decrease in the amounts of saturated fatty acids available for phospholipid synthesis.     

Environmentally-induced changes in the neutral lipids and intracellular vesicles of Saccharomyces cerevisiae and Kluyveromyces fragilis

Saccharomyces cerevisiae, grown aerobically or anaerobically under conditions which induce a requirement for a sterol and an unsaturated fatty acid, synthesized approximately the same amounts of neutral lipid and intracellular low-density vesicles, although the neutral lipids in aerobically-grown cells contained more esterified sterol and less triacylglycerol than those in anaerobically-grown cells. Kluyveromyces fragilis synthesized much less neutral lipid and a smaller quantity of low-density vesicles than S. cerevisiae whether grown at 30°C (generation time 1.1 h) or 20°C (generation time 2.1 h). Both yeasts synthesized highly saturated triacylglycerols, relatively unsaturated phospholipids, and esterified sterols with an intermediate degree of unsaturation irrespective of the conditions under which they were grown. Free sterols in the yeasts were rich in ergosterol and 22(24)-dehydroergosterol, while the esterified sterol fractions were richer in zymosterol.     

Membrane polyunsaturated fatty acids and lithium-sodium countertransport in human erythrocytes

Two groups of individuals, 26 normotensive normolipemic and 37 normotensive hyperlipemic, all without family history of hypertension have been selected in attempt to demonstrate whether Li-Na countertransport of erythrocytes is influenced by plasma and membrane lipid composition. The maximal rate of Li-Na countertransport was elevated in hyperlipemics (0.344 +/- 0.168 vs 0.220 +/- 0.074 mmol/l erythrocytes/h). This difference is highly significant. Hyperlipemics had different composition of membrane lipids than normals. The most important variations were: increase of palmitic, palmitoleic and total saturated fatty acids (SFA) as well as increase of cholesterol/phospholipids ratio (C/PL); in contrast, hyperlipemics had a reduced amount of linoleic acid and total unsaturated fatty acids (UFA) as well as total polyunsaturated fatty acids (PUFA). Consequently, UFA/SFA and PUFA/SFA ratios were lower than in normals. Li-Na countertransport was negatively correlated with the amount of PUFA (P less than 0.02), whereas it was positively correlated with the following parameters: oleic/linoleic ratio (p less than 0.02), monounsaturated fatty acids/polyunsaturated fatty acids ratio (p less than 0.03) as well as with the SFA + monounsaturated fatty acid/PUFA ratio (p less than 0.03). These findings suggest that the V max of Li-Na countertransport in erythrocytes is influenced by the lipid composition of the membrane.     

Characterization of the total lipid and fatty acid composition of rat olfactory mucosa

Phospholipid accounted for 81% (by weight) of the total lipid of rat olfactory mucosa. Phosphatidylcholine (46% of total phospholipids) and phosphatidylethanolamine (26%) were the predominant phospholipids. Phosphatidylinositol (8%), sphingomyelin (6%), and phosphatidylserine (7%) were the next most abundant phospholipids, with cardiolipin (4%) and phosphatidic acid (1%) present in lesser amounts. Only trace amounts of the polyphosphoinositides, phosphatidylinositol monophosphate, and phosphatidylinositol bisphosphate were detected. Sterol was the major neutral lipid present (83% of the total neutral lipid mass) with lesser amounts of triacylglycerols (7%), steryl esters (6%), free fatty acids (4%), and diacylglycerols (1%). Monoacylglycerols were detected only in trace amounts. The sterol to phospholipid ratio was 0.39:1. Most of the phospholipids of the olfactory mucosa showed a high polyunsaturated fatty acid content, with the arachidonic acid (20:4) and docosahexaenoic acid (22:6) residues predominating. The fatty acids in sphingomyelin, however, were almost totally saturated and included the 24:0 and 24:1 residues, which were not detected in other phospholipids. Polyunsaturated fatty acids accounted for less than 25% of the total fatty acid of any individual neutral lipid and comprised largely linoleic and arachidonic acids. The results are discussed in relation to the putative role of lipids in olfactory signal transduction.     

Effect of active dry wine yeast storage upon viability and lipid composition

Alterations in the plasma membrane of Active Dry Wine Yeast (ADWY) produce deleterious effects upon yeast fermentation activity. The aim of this study was to evaluate the changes in viability mediated by plasma membrane alterations induced by poor ADWY storage conditions. Yeast recovery was analyzed after growth in optimal medium. The effects upon vitality were measured by impedance variation. Cell membrane functionality was measured by anisotropy and cell lipid composition was also determined. The results showed a reduction in viability of up to 57–87% in the stored yeast. The storage effect increased saturated fatty acids, and reduced unsaturated fatty acids and phospholipid contents. The stored yeast recovery was related to membrane functionality and significant increases in unsaturated fatty acid, sterol and phospholipid concentrations. Good vitality was positively correlated to high unsaturated fatty acid, phosphatidylserine and phosphatidylethanolamine concentrations and negatively to high saturated fatty acid and phosphatidylcholine contents.