Lipid composition of Escherichia coli in relation to resistance to penicillin.

Clinical isolates of Escherichia coli sensitive and resistant to penicillin were compared in lipid composition and 14C-labelled penicillin uptake, as possible factors in resistance. Except for a slight increase in the triglyceride fraction in sensitive strains there were no qualitative or quantitative differences in the classes of extractable lipids present. Gas-liquid chromatography of the phospholipid and triglyceride fatty acids of the polar and non-polar fatty acids of the bound lipids showed that the same kinds of fatty acids were present. There was an increase of myristate in the chloroform-methanol extractable lipids of highly resistant strains accompanied by a rather general decrease of other fatty acids. Gas-chromatographic analysis of the polar-bound lipids showed an increase of the beta-hydroxydecanoic acid in the resistant strains. By studying the uptake of 14C-labelled benzylpenicillin and the crypticity of the beta-lactamase, evidence has been produced that a decreased permeability of resistant strains to penicillin cooperates with beta-lactamase to induce a high level of resistance. The altered lipid metabolism may reflect the special architectural changes in the cell wall which cause decreased permeability.     

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.     

Survey of extreme solvent tolerance in gram-positive cocci: membrane fatty acid changes in Staphylococcus haemolyticus grown in toluene

We exploited the unique ecological niche of oil fly larval guts to isolate a strain of Staphylococcus haemolyticus which may be the most solvent-tolerant gram-positive bacterium yet described. This organism is able to tolerate 100% toluene, benzene, and p-xylene on plate overlays and saturating levels of these solvents in monophasic liquid cultures. A comparison of membrane fatty acids by gas chromatography after growth in liquid media with and without toluene showed that in cells continuously exposed to solvent the proportion of anteiso fatty acids increased from 25.8 to 33.7% while the proportion of 20:0 straight-chain fatty acids decreased from 19.3 to 10.1%. No changes in the membrane phospholipid composition were noted. Thus, S. haemolyticus alters its membrane fluidity via fatty acid composition to become more fluid when it is exposed to solvent. This response is opposite that commonly found in gram-negative bacteria, which change their fatty acids so that the cytoplasmic membrane is less fluid. Extreme solvent tolerance in S. haemolyticus is not accompanied by abnormal resistance to anionic or cationic detergents. Finally, six strains of Staphylococcus aureus and five strains of Staphylococcus epidermidis, which were not obtained by solvent selection, also exhibited exceptional solvent tolerance.     

Lipid alterations in cell envelopes of polymyxin-resistant Pseudomonas aeruginosa isolates.

The lipid composition of cells of Pseudomonas aeruginosa strains resistant to polymyxin was compared with the lipid composition of cells of polymyxin-sensitive strains as to their content of readily extractable lipids (RELs), acid-extractable lipids, the fatty acid composition of RELs, and the contents of various phospholipids in the REL fraction. The polymyxin-resistant strains had an increased content of RELs, but a decreased phospholipid content. The REL fraction from the polymyxin-resistant strains had an increased content of unsaturated fatty acids accompanied by a decreased content of cyclopropane fatty acids as compared with the fatty acid composition of RELs from polymyxin-sensitive strains. The phosphatidylethanolamine content was greatly reduced in the polymyxin-resistant strains, whereas the content of an unidentified lipid, thought to be a neutral lipid lacking either a phosphate, free amino, or choline moiety, was greatly increased. Cell envelopes of the polymyxin-resistant strains contained reduced concentrations of Mg2+ and Ca2+ as compared with the cell envelopes of polymyxin-sensitive strains. It appears that polymyxin resistance in these strains is associated with a significant alteration in the lipid composition and divalent cation content of the cell envelope.     

Lipopolysaccharide Layer Protection of Gram-Negative Bacteria Against Inhibition by Long-Chain Fatty Acids

Growth, amino acid transport, and oxygen consumption of Escherichia coli and Salmonella typhimurium are inhibited by short-chain (C(2)-C(6)) but not by medium or long-chain fatty acids (C(10)-C(18)) at concentrations at which these processes are completely inhibited in Bacillus subtilis. The resistance of gram-negative organisms is not correlated with their ability to metabolize fatty acids, since an E. coli mutant unable to transport oleic acid is still resistant. However, mutants of both E. coli and S. typhimurium in which the lipopolysaccharide layer does not contain the residues beyond the 2-keto-3-deoxyoctonate core are inhibited by medium (C(10)) but not by long-chain (C(18)) fatty acids. Furthermore, removal of a portion of the lipopolysaccharide layer by ethylenediaminetetraacetate treatment renders the organisms sensitive to medium and partially sensitive to long-chain fatty acids. The intact lipopolysaccharide layer of gram-negative organisms apparently screens the cells against medium and long-chain fatty acids and prevents their accumulation on the inner cell membrane (site of amino acid transport) at inhibitory concentrations. These results are relevant to the use of antimicrobial food additives, and they allow the characterization of gram-positive versus gram-negative bacteria and their lipopolysaccharide mutants.     

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.     

Survey of Extreme Solvent Tolerance in Gram-Positive Cocci: Membrane Fatty Acid Changes in Staphylococcus haemolyticus Grown in Toluene

We exploited the unique ecological niche of oil fly larval guts to isolate a strain of Staphylococcus haemolyticus which may be the most solvent-tolerant gram-positive bacterium yet described. This organism is able to tolerate 100% toluene, benzene, and p-xylene on plate overlays and saturating levels of these solvents in monophasic liquid cultures. A comparison of membrane fatty acids by gas chromatography after growth in liquid media with and without toluene showed that in cells continuously exposed to solvent the proportion of anteiso fatty acids increased from 25.8 to 33.7% while the proportion of 20:0 straight-chain fatty acids decreased from 19.3 to 10.1%. No changes in the membrane phospholipid composition were noted. Thus, S. haemolyticus alters its membrane fluidity via fatty acid composition to become more fluid when it is exposed to solvent. This response is opposite that commonly found in gram-negative bacteria, which change their fatty acids so that the cytoplasmic membrane is less fluid. Extreme solvent tolerance in S. haemolyticus is not accompanied by abnormal resistance to anionic or cationic detergents. Finally, six strains of Staphylococcus aureus and five strains of Staphylococcus epidermidis, which were not obtained by solvent selection, also exhibited exceptional solvent tolerance.     

Variations in the membrane fatty acid composition of resistant or susceptible Leuconostoc or Weissella strains in the presence or absence of Mesenterocin 52A and Mesenterocin 52B produced by Leuconostoc mesenteroides subsp. mesenteroides FR52

Mesenterocins 52A (Mes52A) and 52B (Mes52B) are antimicrobial peptides produced by Leuconostoc mesenteroides subsp. mesenteroides FR 52. Mes52A is a class IIa bacteriocin of lactic acid bacteria with a broad spectrum of activity. Mes52B is an atypical class II bacteriocin with a narrow spectrum of activity. Four Leuconostoc and Weissella wild-type strains were selected for their susceptibility or insensitivity to these mesenterocins. Four strains resistant to Mes52A or Mes52B were generated from the three susceptible wild-type strains by increasing bacteriocin concentrations in culture media. These resistant strains were at least 30 times more resistant than the wild-type strains. No cross-resistance to Mes52A and Mes52B was observed in these strains. No significant differences in membrane fatty acid composition were observed among the three susceptible wild-type strains and the four resistant strains cultured in MRS broth. Thus, the mesenterocin resistance is unlikely to be due to changes in membrane fatty acid composition. When cultured with Mes52A or Mes52B, the membranes of insensitive and resistant strains contained more saturated fatty acids (1 to 10% more) and less unsaturated fatty acids (3 to 6% less), resulting in a more rigid membrane. Thus, the presence of mesenterocin in the culture media of insensitive or resistant strains induced a significant increase in saturated fatty acid contents and a decrease in unsaturated fatty acid contents. Weissella paramesenteroides DSM 20288BR, resistant to Mes52B, responded atypically, probably due to the production of an inhibitor.     

Occurrence,localization, and possible significance of an ornithine-containing lipid in Paracoccus denitrificans

A ninhydrin-positive, phosphorus-negative lipid from Paracoccus denitrificans ATCC 13543 has been isolated and purified by mild alkaline methanolysis followed by silicic acid column chromatography and preparative thin-layer chromatography. The lipid was identified as an ornithine-containing lipid. The major ester-linked fatty acid was cis vaccenic acid. Major amide-linked fatty acids were 3-OH-20:1 and 3-OH-18:0. Ornithine-containing lipid was a major lipid component of P. denitrificans. Phospholipids made up about 57% and ornithine-containing lipid about 14% of the weight of the total lipid of the organism. The ratios of lipid ornithine: lipid phosphorus were 0.23, 0.65 and 0.58 in cytoplasmic membrane, outer membrane, and an NaCl extract, which is thought to represent chiefly outer membrane, respectively. Thus ornithine-containing lipid appears to be present in larger amounts in outer membrane than cytoplasmic membrane. No substantial variations in lipid ornithine levels were noted in stationary phase versus exposnential phase organisms, organisms grown in complex medium versus organisms grown in minimal medium with and without amino acid supplements, or in organisms grown in low phosphate-containing medium.Non standard abbreviations TLC thin-layer chromatography - Tris-HCl tris(hydroxymethyl)aminomethane hydrochloride - TMS trimethylsilyl - TFA triluoroacetyl - NPPN ninhydrin-positive, phosphorus-negative - ECL equivalent chain length     

Composition and positional distribution of fatty acids in polar lipids from Chlorella ellipsoidea differing in chilling susceptibility and frost hardiness

The composition and positional distribution of fatty acids in the polar lipids from 4 strains of Chlorella differing in chilling susceptibility and frost hardiness were analyzed by enzymatic hydrolysis and gas-liquid chromatography. Analysis of the polar lipids from chilling-sensitive, chilling-resistant and chilling-sensitive revertant strains of Chlorella ellipsoidea IAM C-102 showed that the sum of palmitic and trans -3-hexadecenoic acid in phosphatidylglycerol (PG) is about 60% for the sensitive strains and 53% for the resistant strain. The sum of dipalmitoyl and 1-palmitoyl-2-( trans -3-hexadecenoyl) PG as estimated from the positional distribution of their fatty acids, is about 10% in the case of each of the three strains. The contents of unsaturated fatty acids in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were higher in the resistant than in the sensitive strain. This suggests that unsaturation of fatty acids in not only PG but also PC and PE is involved in chilling sensitivity of Chlorella . On the other hand, lipid changes during the development of frost hardiness of C. ellipsoidea IAM C-27, a frost hardy strain, were examined. The results showed that fatty acids in most lipid classes are unsaturated in the hardening process but their degree of unsaturation is not greatly different from that of the chilling-resistant strain, suggesting that not only unsaturation of fatty acids in lipids but also other factors are necessary for the development of frost hardiness.     

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.     

Sterol and fatty acid composition of polyene macrolide antibiotic resistant Torulopsis glabrata.

Successive reculturing of Torulopsis glabrata on media containing increasing concentration of the polyene macrolide antibiotics nystalin or lucensomycin resulted in the segregation of cultures resistant to these antibiotics. Isolates resistant to lucensomycin showed good resistance to nystatin, and vice versa. Analysis of the sterols and fatty acids of sensitive and polyene resistant T. glabrata revealed that compositional changes occurred in both classes of lipids upon acquistion of resistance. The sterol composition of nystatin and lucensomycin resistant cultures possessed reduced amounts of, or no ergosterol (the major sterol of the sensitive parent culture), and increased amounts of sterols which were biogenetically more primitive than ergosterol. Resistant cultures in which ergosterol was absent possessed a fatty acid composition that did not differ significantly from the parent sensitive culture grown under identical conditions. Resistant cultures containing significantly reduced amounts of ergosterol were found to possess altered fatty acid compositions. Generally it was observed that these latter cultures possessed fatty acids containing shorter and more saturated chains. These results are considered to indicate that alteration in both lipid and sterol composition is involved in determination of culture resistance to polyene macrolides.     

Analysis of lipids by gas-liquid chromatography and complementary methods in four strains of Aedes aegypti mosquitoes

Fatty acid composition of total lipids, neutral lipids and phospholipids of strains of Aedes aegypti were determined. The fatty acid composition of the strains differed quantitatively with regard to the relative percentage of commonly occurring fatty acids. Gas-liquid chromatography of fatty acid methyl esters showed 18:1 (oleic or elaidic) to be the predominant fatty acid. The fatty acid was identified as oleic by argentation thin-layer chromatography. A modified colorimetric method was used to determine tissue-free fatty acids. The lipids were predominantly triacylglycerol with lesser amounts of free fatty acids and decreasing amount of sterol ester, sterol, monoacylglycerol, diacylglycerol and hydrocarbons. The data show considerable lipid differences between the Caribbean strains (Les Cayes, Haiti, and San Juan, Puerto Rico) and the Jakarta (Indonesia) strain. The Shimba Hills (Kenya) strain was more similar to Jakarta than to the Caribbean strains. The results obtained with the different strains are discussed in relation to the established oral susceptibility to Dengue 1 and Dengue 2, yellow fever, and genetic analysis by isoenzyme studies.     

Membrane fluidity and lipid composition in clinical isolates of Candida albicans isolated from AIDS/HIV patients

In this study, we describe the membrane lipid composition of eight clinical isolates (azole resistant and sensitive strains) of Candida albicans isolated from AIDS/ HIV patients. Interestingly, fluorescence polarization measurements of the clinical isolates displayed enhanced membrane fluidity in fluconazole resistant strains as compared to the sensitive ones. The increase in fluidity was reflected in the change of membrane order, which was considerably decreased (decrease in fluorescence polarization "p" value denotes higher membrane fluidity) in the resistant strains. The ergosterol content in azole susceptible isolates was greater, almost twice as compared to the resistant isolates. However, no significant alteration was observed in phospholipid and fatty acid composition of these isolates. Labeling experiments with fluorescamine dye revealed that the percentage of phosphatidylethanolamine exposed to the membrane's outer leaflet was higher in the resistant strains as compared to the sensitive strains, indicating increased floppase activity of the two major ABC drug efflux pumps, CDR1 and CDR2 possibly due to their overexpression in resistant strains. The results of the present study suggest that changes in the status of membrane lipid phase especially the ergosterol content and increased activity of drug efflux pumps by overexpression ofABC transporters, CDR1 and CDR2 might contribute to fluconazole resistance in C. albicans isolated from AIDS/HIV patients.     

Preparation and characterization of membrane fractions enriched in outer and inner envelope membranes from spinach chloroplasts. II. Biochemical characterization

In the previous paper (Block, M. A., Dorne, A.-J., Joyard, J., and Douce, R. (1983) J. Biol. Chem. 258, 13273-13280), we have described a method for the separation of membrane fractions enriched in outer and inner envelope membranes from spinach chloroplasts. The two envelope membranes have a different weight ratio of acyl lipid to protein (2.5-3 for the outer envelope membrane and 0.8-1 for the inner envelope membrane). The two membranes also differ in their polar lipid composition. However, in order to prevent the functioning of the galactolipid:galactolipid galactosyltransferase during the course of envelope membrane separation, we have analyzed the polar lipid composition of each envelope membrane after thermolysin treatment of the intact chloroplasts. The outer envelope membrane is characterized by the presence of high amounts of phosphatidylcholine and digalactosyldiacylglycerol whereas the inner envelope membrane has a polar lipid composition almost identical with that of the thykaloids. No phosphatidylethanolamine or cardiolipin could be detected in either envelope membranes, thus demonstrating that the envelope membranes, and especially the outer membrane, do not resemble extrachloroplastic membranes. No striking differences were found in the fatty acid composition of the polar lipids from either the outer or the inner envelope membrane. The two envelope membranes also differ in their carotenoid composition. Among the different enzymatic activities associated with the chloroplast envelope, we have shown that the Mg2+-dependent ATPase, the UDP-Gal:diacylglycerol galactosyltransferase, the phosphatidic acid phosphatase, and the acyl-CoA thioesterase are associated with the inner envelope from spinach chloroplasts whereas the acyl-CoA synthetase is located on the outer envelope membrane.     

Study of the action of nystatin on the plasmatic membranes of the liver of rabbits]

The effect of mystatin on the plasmic membranes of the rabbit liver after intravenous administration of the antibiotic to the animals in a dose of 5 mg/kg was studied. It was found that intravenous administration of nystatin had no effect on the quantitative content of protein, lipids and nucleic acids in the plasmic membranes of the liver. The method of electrophoresis in polyacrylamide gel revealed significant changes in the composition of the liver membrane protein due to the treatment with nystatin. The effect of nystatin on the composition of lipids and fatty acids contained in the membrane lipids was also investigated. The data of the thin layer chromatography showed that nystatin did not affect the qualitative composition and the content of separate lipid fractions in the lipids of the liver plasmic membranes. However, the fatty acid analysis of the membrane lipids after intravenous administration of nystatin revealed a number of qualitative and quantitative differences in the composition of the lipid fatty acids of the membranes tested. The results showed that nystatin affected the membrane structures of the rabbit liver cells.     

Lipids of antibiotic-resistant and -susceptible members of the Enterobacteriaceae.

Lipids of antibiotic-resistant and related -susceptible strains of the Enterobacteriaceae were extracted with chloroform-methanol and characterized by thin-layer chromatography, densitometry, and fatty acid analysis using gas chromatography. Quantitative differences which correlated with antibiotic resistance existed among the phospholipids and fatty acids. A relatively higher concentration of a ninhydrin-positive phospholipid concentration with a lower amount of phosphatidylethanolamine was observed in antibiotic-resistant strains of serratia marcescens. Bacterial strains which harbored R-factor 222 had a higher ratio of phosphatidylglycerol to diphosphatidylglycerol than their respective parent strains while those strains which were resistant to the polymyxins had a lower ratio of these phospholipids. Differences in the relative amounts of certain unsaturated and cyclopropane fatty acids were observed between susceptible and resistant strains. Such differences, however, were dependent upon a particular genus and species.     

Characteristics of the composition of higher fatty acids in methicillin-resistant and methicillin-sensitive Staphylococci

The composition of fatty acids of methicillin-resistant (MR) and methicillin-sensitive (MS) strains of Staph. aureus and Staph. epidermidis was determined with the method of reactive gas liquid chromatography. The MS staphylococci of the above species differed by the content of acids with branched chains of iso- and anteisostructures and straight chains. Anteisoacids in the cells of Staph. epidermidis amounted almost to 80 per cent of the total number of the acids, while in the cells of Staph. aureus, their total number amounted only to a half of the fatty acid pool. Comparison of the composition of the fatty acids of the MS and MR strains of Staph. aureus revealed differences in the proportions of the anteiso- and isoacids. The total number of the long-chain C20.0 acid in the cells of Staph. epidermidis resistant to methicillin was lower as compared to that in the sensitive cells.     

Lipid composition of isolated epiphyseal cartilage cells, membranes and matrix vesicles.

1. Intact cells, cell fragments (membranes) and matrix vesicles were isolated from the proliferating and calcifying layers of epiphyseal cartilage by sequential hyaluronidase and collagenase digestion and differential centrifugation. Lipids were extracted and analyzed for various lipid classes and their fatty acid composition by column, thin-layer, paper and gas-liquid chromatography. 2. On a protein basis the isolated matrix vesicles had more total lipid than either the membrane or cell fractions, the vesicles and membranes being richer in non-polar lipids and containing smaller quantities of phospholipids than whole cells. Expressed as a percentage of the total lipid, the cells were richer in triacylglycerols and lower in free fatty acids than in the membrane or vesicle fractions. The proportion of free cholesterol and the cholesterol/phospholipid ratio were nearly twice as high in the matrix vesicles as in the other tissue fractions. Choline and ethanolamine phosphoglycerides progressively declined in the membrane and matrix vesicle fractions, whereas serine phosphoglycerides and sphinogomyelin increased. Non-phosphorus-containing polar lipids were present in all fractions, the vesicles being richer in polyhexosyl ceramides, cerebrosides, glycosyldiacylglycerols and certain uncharacterized acidic polar lipids. 3. Fatty acid patterns of the matrix vesicles were distinctive from those of isolated cells, being generally richer in 18 : 0 and 18 : 2, and lower in 16 : 1 and 18 : 1 fatty acids. Monoacyl forms were similarly increased in 16 : 0 and/or 18 : 0, and reduced in 16 : 1, 18 : 1 or 20 : 2 fatty acids, depending on the lipid class. The fatty acid composition of diphosphatidylglycerol from cells and matrix vesicles was markedly different, providing evidence that the cardiolipin in the vesicles was not from mitochondrial components. 4. Based on the fact that the matrix vesicles were significantly enriched in free cholesterol, sphingomyelin, glycolipids and serine-phosphoglycerides, it is concluded that they are derived from the plasma membrane of the cell, supporting earlier conclusions based upon morphological and enzymological evidence.     

Lipid and Fatty Acid composition of chloroplast envelope membranes from species with differing net photosynthesis

Lipid and fatty acid compositions were determined for chloroplast envelope membranes isolated from spinach (Spinacia oleracea L.), sunflower (Helianthus annuus L.), and maize (Zea mays L.) leaves. The lipid composition was similar in sunflower, spinach, and undifferentiated maize chloroplast envelope membranes and different in maize mesophyll chloroplast envelope membranes. The predominant lipid constituents in all envelope membranes were monogalactosyldiglyceride (27 to 46%), digalactosyldiglyceride (18 to 33%), and phosphatidylcholine (7 to 30%). The fatty acid composition was also similar in sunflower and spinach chloroplast envelope membranes in comparison to those from maize. The major acyl fatty acids of the chloroplast envelope membrane were palmitic (C_16:0, 41 and 36%) and linolenic (C_18:3, 29 and 40%) acids for spinach and sunflower; palmitic (77%) and stearic (C_18:0, 12%) acids for young maize; and palmitic (61%), stearic (14%), and linolenic (13%) acids for mature maize. The differences in lipid and acyl fatty acid compositions among these plants which vary in their rates of net photosynthesis were largely quantitative rather than qualitative.