Thermophilic fungi: II. Fatty acid composition of polar and neutral lipids of thermophilic and mesophilic fungi

The relative per cents of polar and neutral lipids and the fatty acid profile of the polar and neutral lipids of nine thermophilic and nine mesophilic fungi were examined and compared. The polar lipids of the thermophiles contained an average of 0.89 double bonds per mole fatty acid (unsaturation index, USI) and were considerably more saturated than the corresponding lipids of the mesophiles (average 1.32 USI). Within the thermophilic species the polar lipids were generally more saturated than the neutral lipids (average 0.95 USI) and in the mesophilic species the polar lipids were usually more saturated than the neutral lipids (average 1.14 USI). The mesophiles produced higher levels of 16∶1, 18∶2 and 18∶3 fatty acids than the thermophiles and preferentially incorporated 16∶1 and 16∶2 into their polar lipids. The thermophiles produce higher levels of saturated fatty acids and 18∶1 than the mesophiles and preferentially incorporated the saturated fatty acids into their polar lipids.     

Neutral Lipid Characterization of Non-Water-Soluble Fractions of <Emphasis Type="Italic">Carica Papaya</Emphasis> Latex

The non-water-soluble fraction of Carica papaya latex (CPL) constitutes a waste material from papain production; very little information exists regarding its chemical composition. The non-water-soluble fraction of CPL was fractionated by liquid chromatography into neutral lipids, glycolipids and phospholipids. The most abundant compounds were found to be the polar lipids, accounting for 79.2% (w/w) of the total extractible matter, while the total amount of neutral lipids was only around 20%. It was composed of free fatty acids, sterols and triterpenic alcohols, but no glycerides were detected. A high content of saturated fatty acids was measured; these saturated fatty acids were represented by very long chains with C24:0, C26:0 and C28:0 accounting for 6.3, 11.0 and 6.3%, respectively, in the total extractible matter and 7.3, 9.0 and 3.9% in the FFA fraction. The monounsaturated fatty acids were about 23–25% in both samples, with oleic acid (C18:1) being the most abundant. The polyunsaturated fatty acids that were 25.1% in the total matter and 21.6% in the FFA fraction were mainly represented by linoleic acid (C18:2n-6). Finally, a very interesting characteristic of the FA composition of this latex concerns the presence of odd-numbered fatty acids in significant amounts (around 22% in the total extract and 24.3% in the FFA fraction).     

Studies on physicochemical characteristics and fatty acid composition of lipids produced by a strain ofRhodotorula gracilis CFR-1

Rhodotorula gracilis CFR-1 has been evaluated for its potential to produce lipids. The yeast lipids closely resembled palmolein, a liquid fraction of palm oil. It contained 2.3–3% free fatty acids, 64.4% tri-, 23.1% di-, and 6.1% mono-acylglycerols, 94.2% neutral and 5.8% polar lipids. Most abundant fatty acids were C18∶1, C16∶0, C18∶2 and C18∶0 (43.8, 28.5, 13.5 and 4.5%). All fatty acids, irrespective of the levels, followed definite patterns of increase or decrease during the advancement of fermentation. A pincers-shaped curve was obtained when the total saturation and unsaturation were plotted. Use of different glucose and molasses-based media did not show any significant overall effect on saturation (34.4–39.5%) and unsaturation (60.4–65.3%). Desaturation of fatty acids was found to be a metabolic function occurring in the process of cell maturation.     

Fatty acid composition of phospholipids and neutral lipids during embryonic and early larval development in Atlantic herring (Clupea harengus,L.)

The fatty acid compositions of total polar and total neutral lipids of Atlantic herring eggs and larvae were determined immediately before fertilization, after fertilization and at various times during subsequent embryonic and early larval development. Within 3 hr after fertilization the percentage of total PUFA in neutral lipid decreased from 33% to 20%, with a reciprocal increase in monoenes. Thereafter the percentage of PUFA in the neutral lipids increased progressively, attaining the original level in ripe eggs by the time of yolk sac absorption. During the larval stages the percentage of PUFA continued to increase in the neutral lipid, reaching almost 44% of the total by day 32 after fertilization, although it was reduced to 32% by day 36. The percentage of monoenes in the neutral lipid displayed a progressive decrease during the whole period of development from 3 hr after fertilization. Throughout all the developmental periods the fatty acid composition of total polar lipids remained essentially constant. The polar lipids of the yolk sac displayed virtually the same fatty acid composition as the larval bodies, but the neutral lipids of the yolk sac were low in PUFA compared to the larval bodies. The results are discussed with reference to changes in lipid class composition during development. The conservation of high levels of PUFA in lipids during embryogenesis and early larval development reflects the importance of these fatty acids during development.     

Effect of vacuum‐packaging on the changes of Russian sturgeon muscle lipids during frozen storage

The changes in fatty acid composition, non‐polar (triglycerols) and polar lipids (phospholipids), total free fatty acids and total cholesterol of Russian sturgeon (Acipenser gueldenstaedtii) were studied during 360 days of storage at ?18°C. It was established that total neutral lipids and phospholipids content decreased and total free fatty acids concentration increased significantly during the frozen storage. Lower non‐polar and polar lipids content and higher free fatty acids concentration of vacuum‐packaged samples in comparison with air‐packaged samples were found. The changes in total cholesterol concentration and phospholipid classes of frozen stored sturgeon were not influenced by the frozen storage period and the type of packaging. It was established that the sturgeon polar lipids consisted mainly of phosphatidylcholine – 54.98 ± 0.85%, phosphatidylethanolamine – 28.42 ± 0.61%, and phosphatidylserine – 8.64 ± 0.45%. The increase of the total free fatty acids concentration was associated with the free n ? 3 PUFA accumulation as a result of hydrolysis of non‐polar and polar lipids. During the frozen storage DHA percentage of non‐polar lipids and phospholipids decreased approximately 3 and 1.75%, respectively. After 360 days of storage at ?18°C the n ? 3/n ? 6 PUFA ratio of total lipids decreased 4.9%.     

Polyunsaturated fatty acids and neutral lipids in developing larvae of the oyster,Crassostrea virginica

The fatty acid composition of oyster larvae at various stages, as well as of the algal diet, were determined by gas liquid chromatography (GC). Saturated fatty acids are the major fatty acid components in all larval stages and account for 34–62%, 30–35% and 35–81% of the neutral, polar and total lipids of algal-fed larvae respectively. Weight percentage of saturated fatty acid in “starved” larvae was consistently higher (63–81%) during the whole period. The total polyunsaturated fatty acids were higher in the polar lipids than in the neutral lipids. The concentration of the ω3 fatty acids also was comparatively higher in the polar lipids than in the neutral lipids. In the total and neutral lipid fractions, the weight percentage of polyunsaturated and ω3 fatty acids was higher in the eyed than in the pre-eyed (pediveliger) larvae. Eicosapentaenoic acid (20∶5ω3) and 22∶6ω3 were not detected in lipids of “starved” and young larvae. There was an accumulation of 20∶5ω3, 22∶6ω3, and total ω3 fatty acids in the older larvae. Lipid classes were separated by thin layer chromatography (TLC). There was no qualitative change in lipid composition during larval development, but a marked increased of triacylglycerol in larvae up to the stage of maturation in algae-fed larvae. Contribution number 1195 of the Virginia Institute of Marine Science, Gloucester Point, VA 23062     

Fungi pathogenic to insects: III. Neutral and polar lipids ofEntomophthora coronata

The neutral and polar lipid composition ofEntomophthora coronata was determined qualitatively. The fungus was grown on a chemically nondefined medium (Sabouraud dextrose yeast extract) and a chemically defined medium for a period up to 26 days. The lipids were characterized by thin-layer, column, gas chromatography, and selective sprays,³²P-labeling, and mass spectrometry. The neutral lipids consist of monoglycerides, diglycerides, cholesterol, free fatty acids, triglycerides, and cholesteryl esters. The polar lipids consist of phospholipids (phosphatidyl ethanolamine, phosphatidyl choline, lysophosphatidyl ethanolamine, lysophosphatidyl choline, and spingomyelin), a number of glycolipids including cerebrosides, and many unrecognizable lipids, most of which are present in trace amounts. The cerebrosides and spingomyelin are present in significant amounts, and their concentration increased with age of the culture. The major fatty acids (>10%) of the total, neutral, and polar lipids of the mycelia are 14∶0, 16∶0, 18∶1, 18∶3(γ), and 24∶1. The polar lipids of total culture (unsaturation index 0.88) and of the conidia (unsaturation index 1.48) are considerably more unsaturated than the corresponding neutral lipids (unsaturated index 0.50 and 0.49). The mycelial polar lipids, compared to the neutral lipids, possess less 14∶0 and 18∶1 but contain a greater percentage of 16∶0, 18∶2, 18∶3(γ), 24∶0, and 24∶1. The major fatty acid of the conidia (>10%) are 13∶0, 14∶0, 18∶1, 18∶2, 18∶3(γ), and 20∶4. Their polar lipids have a higher proportion of 18∶2, 18∶3(γ), and 20∶4. The cerebrosides possess 24.1 in high relative proportion (30.1%). Presented at the AOCS Meeting, Atlantic City, October 1971.     

Lipid and alkali extractable fatty acids fromMucor rouxii: Effect of thermal changes in growth environment and age of cells

The lipid levels of the fungusMucor rouxii are affected markedly by both the growth temperature and the age of the cells. Both chloroform-methanol extractable (fraction I) and alkali extractable (fraction II) fatty acids are present in these cells, and the fraction II/fraction I ratio increased significantly with decreasing growth temperature. This ratio was, however, reasonably constant during the entire growth period at each specific growth temperature. In all cases, the unsaturation index of the fraction II fatty acids was significantly lower than the corresponding value for the fraction I fatty acids. Examination of the unsaturation indeces of the two fractions during the early log-phase growth period (48 hrs) indicated that the indeces decreased with increasing growth temperature; however, as the age of the cells increased, this relationship changed dramatically. At the end of 144 hrs growth, the unsaturation index for fraction II has reversed its temperature dependance completely, since the index is a maximum at the higher growth temperature. The degree of unsaturation for fraction I is a maximum at 25 C and is lower for cells grown at 15 and 35 C; this relationship is true between 96–144 hr after inoculation.     

Changes in lipids of pigeon “milk” in the first week of its secretion

Pigeon “milk” (PM) collected from the crop of 1- to 5-day-old squabs was analyzed to examine whether there were changes in lipid composition during the first week of secretion. The high PM fat content (9–11%) remained fairly constant in the first 5 days of secretion. The mean percentage of neutral lipids, glycolipids and phospholipids was 80, 12 and 8%, respectively. Unlike the content of neutral lipids, glycolipid and phospholipid levels increased significantly between day 1 and day 5 of secretion. Triglycerides, the major neutral lipids, decreased by 24% between day 1 and day 5, while free sterols, monoglycerides and hydrocarbons increased by 8%, 11% and 2.5%, respectively, during the same period; diglycerides and sterol esters, however, remained unchanged. The ratio of saturated to unsaturated fatty acids was 0.27 and it remained unchanged. Medium-chain (C₁₀, C₁₂ and C₁₄) and oddchain (C₁₅ and C₁₇) fatty acid contents were low. Fatty acids longer than C₂₀ were absent. Palmitic acid, the major saturated fatty acid, increased by 42% from day 1 to day 5, whereas stearic acid decreased by 48% during the same period. Oleic acid, the predominant unsaturated fatty acid, also decreased from 51 to 45% between the first and fifth day of PM secretion. Polyunsaturated acids (18∶2, 18∶3 and 20∶4) accounted for 26% and 30% of the total fatty acids on day 1 and day 5, respectively. Although lipid changes in the crop of squabs prior to collection of samples cannot totally be ruled out, the nature of lipid changes is likely to reflect cellular breakdown that precedes PM secretion by parent pigeons.     

Sphingophosphonolipids, phospholipids, and fatty acids from aegean jellyfish Aurelia aurita

The goal of this study is to elucidate and identify several sphingophosphonolipids from Aurelia aurita, an abundant but harmless Aegean jellyfish, in which they have not previously been described. Total lipids of A. aurita were 0.031-0.036% of fresh tissue, and the lipid phosphorus content was 1.3-1.7% of total lipids. Phosphonolipids were 21.7% of phospholipids and consisted of a major ceramide aminoethylphosphonate (CAEP-I; 18.3%), as well as three minor CAEP (II, III, IV) methyl analogs at 1.3, 1.1, and 1.0%, respectively. The remaining phospholipid composition was: phosphatidylcholine, 44.5%, including 36.2% glycerylethers; phosphatidylethanolamine, 18.6%, including 4.5% glycerylethers; cardiolipin, 5.6%; phosphatidylinositol, 2.6%; and lysophosphatidylcholine, 5.0%. In CAEP-I, saturated fatty acids of 14-18 carbon chain length were 70.8% and were combined with 57.3% dihydroxy bases and 23.4% trihydroxy bases. The suite of the three minor CAEP methyl analogs were of the same lipid class based on the head group, but they separated into three different components because of their polarity as follows: CAEP-II and CAEP-III differentiation from the major CAEP-I was mainly due to the increased fatty acid unsaturation and not to a different long-chain base, but the CAEP-IV differentiation from CAEP-I, apart from fatty acid unsaturation, was due to the increased content of hydroxyl groups originated from both hydroxy fatty acids and trihydroxy long-chain bases. Saturated fatty acids were predominant in total (76.7%), polar (83.0%), and neutral lipids (67.6%) of A. aurita. The major phospholipid components of A. aurita were comparable to those previously found in a related organism (Pelagia noctiluca), which can injure humans.     

Salivary lipid profiles of the leech (Hirudo medicinalis)

Saliva was collected from sixteen leeches (Hirudo medicinalis). The saliva was analyzed for its total lipid content (3.26±0.31 mg of total lipids per 100 mL saliva). The lipids were separated into polar and nonpolar by chromatographic techniques. The neutral fraction was approximately 2/3 of the total, and the polar fraction was approximately 1/3 of the total lipids. Thin-layer chromatography was used to obtain the individual profiles of the polar and nonpolar lipids. Of the identified lipids, phosphatidic acids and free fatty acids represented the largest percentage. These results suggest that the leech contains a unique lipid distribution, and that some of these components may be potent phospholipases and lipases that probably are present in its saliva for the purpose of preventing plugging or healing of the wound in the attacked organism.     

Rapid separation of neutral lipids,free fatty acids and polar lipids using prepacked silica sep-Pak columns

A method is described for the separation of neutral lipid, free fatty acid and polar lipid classes using small (600 mg), prepacked silica Sep-Pak columns. Combinations of hexane and methyltertiarybutylether were used to progressively elute cholesteryl ester first then triglyceride from the column. After column acidification, fatty acids were eluted followed by cholesterol. Recoveries of these lipids were 96% or greater. Polar lipids were eluted from the column using combinations of methyltertiarybutylether, methanol and ammonium acetate. Phospholipid classes could not be separated completely from each other. Phosphatidylethanolamine and phosphatidylinositol eluted together, whereas the more polar phosphatidylcholine, sphingomyelin and lysophosphatidylcholine were eluted as a second fraction. Recoveries of each phospholipid was greater than 98%.     

Thermophilic fungi: IV. The lipid composition of six species

The lipid composition of six thermophilic fungi (Myriococcum albomyces, Mucor miehei, Papulaspora thermophila, Rhizopus sp.,Thielavia thermophila (+)Thielavia thermophila (−), andTorula thermophila) was examined. The relative per cent total lipids (4.9–26.3%), neutral lipids (55.5–88.3%), polar lipids (11.7–44.6%) and the fatty acid profile of each lipid fraction was determined. The predominant fatty acids were 16∶0, 18∶0 and 18∶2, and lesser amounts of 12∶0, 14∶0, 15∶0, 16∶1, 16∶2, 17∶0 and 18∶3 were present. The total lipids contained an average of 0.96 double bonds per mole fatty acid (unsaturation index [USI]) the neutral lipids 0.86 USI and the polar lipids 0.84 USI, excluding the values forTorula thermophila. These data show a high degree of saturation and are consistent with data reported for other fungal thermophiles.Torula thermophila possessed abnormally high USI values (1.15–1.50) and was cultured at three different temperatures (25, 45 and 51 C). As the culture temperature ofTorula thermophila increased, the USI decreased. The USI of the polar lipids ofTorula thermophila at 25, 45 and 51 C were 1.50, 1.28 and 1.11, respectively. Thus the membrane lipids of this fungus appear unusual for a thermophile.     

Lipid composition of normal male rat islets

Lipid composition was studied in fresh isolated isolets from normal male rats. Extractable lipids represent 1856 μg per mg islet protein. In such extracts, phospholipids and neutral lipids reprsent 13.5% and 86.5%, respectively. Phosphatidylcholine (45.8%) and phosphatidyl-ethanolamine (20.6%) were the major components of the phospholipid fraction, and phosphatidylinositol (8.9%) was the minor component. Esterified cholesterol (38.5%), cholesterol (25.5%) and free fatty acids (24.4%) were the major components of the neutral lipid fraction. Fatty major components of the neutral lipid fraction. Fatty acids esterified to phospholipids account for 619.7 pmol/islet, and, 2710 pmol/islet were esterified to neutral lipids. In the phospholipid fraction, saturated and unsaturated fatty acids were in a similar proportion. Conversely, in the neutral lipids, two-thirds of the fatty acids were unsaturated. The ω6 family was the main component of the phospholipid unsaturated fatty acids. In the ω6 and ω3 families, the long-chain fatty acids represent the main components. In the neutral lipid fraction, a different percentage of each family was found: ω3>ω6>ω9. The long-chain polyunsaturated fatty acids were also predominant species in the ω6 and ω3 families. Further studies on the lipid composition of islets, obtained from rats with normal and altered islet functions, could provide new insights into the knowledge of the mechanism of insulin secretion.     

Temperature acclimation in the crayfish: Effects on phospholipid fatty acids

Acclimation to different temperatures by a poikilothermous animal must include modification of its membrane lipids to maintain the proper physical properties. The simplest way to achieve this acclimation would seem to be by modification of the phospholipid fatty acids. In a freshwater cray-fish,Procambarus clarkii, rapid changes in the degree of unsaturation of newly synthesized phospholipid fatty acids were correlated with changes in environmental temperature, both in whole animals and in slices of hepatopancreas tissue. At 5 C, the rate of fatty acid synthesis was about half that occurring at 23 C. Hepatopancreas tissue from animals acclimated to either 5 C or 23 C, when incubated for 2 hr at 5 C, incorporated a higher percentage of exogenous [1-¹⁴C] acetate into polyunsaturated acids (27–38% of the radioactivity in total fatty acids) than when incubated at 23 C (12–14%); conversely, more saturated fatty acids were synthesized at 23 C (73–80% vs 51–73%). The higher average unsaturation of the fatty acids biosynthesized at 5 C constitutes an effective response to the animal's need for modification of lipids to maintain adequate membrane function at the lower environmental temperature. Presented at the AOCS meeting in Mexico City, Mexico, April 27–May 2, 1974. Work done at the Laboratory of Nuclear Medicine and Radiation Biology, University of California, Los Angeles, CA 90024.     

The lipids of corn germ and endosperm

Mature kernels of an inbred corn were hand dissected into germ and endosperm fractions. Among various solvents tested, boiling, water-saturatedn-butanol extracted the most lipid from endosperm, and it was used as t h e extracting solvent for both germ and endosperm. The germ contained 78% of the total lipids and the endosperm 17%. The most striking differences in the fatty acid compositions of the triglycerides and polar lipids were higher levels of stearic and linolenic acids in the endosperm lipids. Although precautions were taken during extraction to inactivate lipases, immediately after harvest the free fatty acid level of the total lipids of the whole kernel was 6.5%. Ninety-five percent of the free fatty acids was in the endosperm fraction where the free fatty acids made up 36.5% of the total lipids. In germ, free fatty acids represented only 0.6% of the total lipids. The individual phospholipid and glycolipid classes of the endosperm and germ lipids were similar except for high levels of lyso compounds in the endosperm lipids. The higher levels of linolenic acid, free fatty acids and lyso lipids in endosperm may affect the keeping quality of the corn grain and of fractions milled from the endosperm. Presented at the AOCS meeting, St. Louis, May 1978.     

The effects of fat-free,saturated and polyunsaturated fat diets on rat liver and plasma lipids

The liver and plasma lipids and fatty acid composition of rats fed synthetic diets of differing fat type and content were studied. All animals were starved for 48 hr and then refed a high carbohydrate, fat-free diet for 48 hr. They were then divided into three groups and fed for an additional 48 hrs the following: group 1, the fat-free diet; group 2, a diet containing 44% of calories from corn oil; and group 3, a diet containing 44% calories from completely hydrogenated soybean oil. The total lipid concentration of the liver in the animals on the fat-free diet was elevated at 72 and 96 hr. The addition of either saturated or unsaturated fat in the diet at 48 hr prevented this accumulation. The total phospholipid and cholesterol concentrations of the liver were relatively uninfluenced by any diet in this study. Plasma total fatty acid concentration was elevated at 72 hr in the animals on a fat-free diet compared to those fed the stock diet, starved for 48 hr or fed the fat-containing diets. By 96 hr, however plasma fatty acid concentrations in all groups were similar to those in animals fed only the stock diet. The release of de novo synthesized fatty acids into plasma from the liver was strongly inhibited by dietary fat, either saturated or polyunsaturated. With the fat-free diet there was a significant increase in the saturated and monounsaturated fatty acids in both liver and plasma. The addition of corn oil to the diet facilitated a reversion of the fatty acid composition in liver and plasma to that found in the animals fed the stock diet ad libitum, but saturated fat did not. No effect of diet on the fatty acid composition of the red cells was observed during the course of this study. Exogenous saturated fatty acids, although similar chemically to the fatty acids synthesized by the liver, may have physiological actions that differ from endogenously synthesized fat.     

Changes in flax (Linum usitatissimum L.) seed lipids during germination

Flax (Linum usitatissimum L.) seeds were germinated for 8 d under laboratory conditions, and changes in their lipid fraction were studied by various chemical and chromatographic methods. Total lipid content of the seeds was reduced fourfold at the end of the 8-d germination period as compared to ungerminated seeds on a fresh weight basis. The neutral lipids comprised the major fraction of seed lipids, and triacylglycerols predominated over all other lipid components even during the germination period. Both the spectrophotometric and thin-layer chromatography-flame-ionization detection methods of quantification showed a considerable increase in the content of free fatty acids. The glycolipid fraction of lipids increased, but the phospholipid fraction exhibited only minor changes. Lipase activity of flaxseed increased at the beginning of germination and then remained constant until the fifth day. Phosphatidylcholine was the major phospholipid of flaxseed lipids, and its content was reduced during the germination. The contents of lysophosphatidylcholine and phosphatidic acid increased from negligible amounts to 46% of the total phospholipids. Linolenic, linoleic, and oleic acids, respectively, were the predominant fatty acids of all the lipid fractions of flaxseed, and remained unchanged during the germination period. The glycolipid fraction had the lowest content of polyunsaturated fatty acids. Fatty acids C_14:0, C_20:0, C_24:0, C_20:1, C_22:1, and C_20:5 appeared after d 2 of germination in neutral, glyco- and phospholipid fractions.     

Polar lipids ofMacrophomina phaseolina

Macrophomina phaseolina was grown on a defined medium at three different carbon/nitrogen ratios. The lipids of the mycelia and the sclerotia were extracted; fractionated into polarity groups; and separated by thin layer, column, and gas liquid chromatographies. Sclerotia contained higher levels of neutral lipids and lower amounts of polar lipids than mycelia. The neutral lipid content of sclerotia increased, up to 77% of total lipids, and phospholipids decreased as carbon/nitrogen ratio increased from 10 to 320. The glycolipid content was not altered significantly by changes in carbon/nitrogen ratios. Although cardiolipin could not be detected in sclerotial polar lipids, both sclerotia and mycelia contained similar phospholipid profiles with major quantitative differences. Phosphatidic acid and phosphatidyl glycerol were major components of sclerotia, whereas phosphatidyl ethanolamine and phosphatidyl inositol were the major phosphatides of mycelia. Phosphatidyl choline was present in both mycelia and sclerotia. The fatty acid distribution did not show any particular pattern of saturation or unsaturation due to differences in carbon/nitrogen ratio. However, mycelial lipids tended to contain C24∶1, C18∶3, and C22∶1 as major fatty acids, whereas the major fatty acids in sclerotial lipids were C18∶2, C18∶1, C22∶1, C20∶0, and C16∶1. Saturated fatty acids were present in lesser concentrations.     

Isovaleric acid as a precursor of odd numbered iso fatty acids in Tetrahymena

Tris isovalerate-supplementedTetrahymena pyriformis W showed no qualitative change in fatty acid composition; however, an increase in polar lipids that contain odd numbered iso acids (C₁₃, C₁₅, C₁₇, C₁₉) occurred. This change was accompanied by a decrease in the proportional amount of even numbered normal acids (C₁₄, C₁₆, C₁₈). The neutral and polar lipids from cells incubated with [1-¹⁴C] isovaleric acid were found to contain radioactivity. The methyl esters of the saturated fatty acids obtained from the polar lipids by alkaline methanolysis were separated by reversed phase chromatography, the identities confirmed by gas chromatography-mass spectrometry, and the specific activities determined. Iso acids were found to be the most heavily labeled materials. In addition to ceramide, two sphingolipid components were detected. One yielded saturated fatty acids after acidic methanolysis, while the other contained >93% α-hydroxy fatty acids. Radioactivity was noted in the long chain base fraction derived from the sphingolipids. Progressive growth inhibition occurred as the isovalerate concentration was increased in the culture medium; however, the ciliates were morphologically indistinguishable from unsupplemented cells.