Activation of host phospholipases C and D in macrophages after infection with Listeria monocytogenes.

Infection of the J774 murine macrophage-derived cell line with Listeria monocytogenes results in several elevations of intracellular calcium during the first 15 min of infection. These appear to result from the actions of secreted bacterial proteins, including phosphatidylinositol-specific phospholipase C (PI-PLC), a broad-range phospholipase C, and listeriolysin O (LLO) (S. J. Wadsworth and H. Goldfine, Infect. Immun. 67:1770-1778, 1999). We have measured hydrolysis of host PI and the activation of host polyphosphoinositide-specific PLC and host phospholipase D (PLD) during infection with wild-type and mutant L. monocytogenes. Elevated hydrolysis of host PI occurred within the first 10 min of infection and was dependent on both bacterial PI-PLC and LLO, both of which were required for the earliest elevations of intracellular calcium in the host cell. A more rapid hydrolysis of host PI was observed at 30 min after infection, at the time when wild-type bacteria have been internalized. Activation of host PLC, also occurred in the first 10 min of infection but was not dependent on the presence of bacterial PI-PLC. Similar observations were made in murine bone marrow-derived macrophages. In J774 cells, activation of host PLD was observed after 20 min of infection and was dependent on bacterial LLO. Mutants in the bacterial phospholipases produced levels of PLD activation similar to those produced by the wild type. Phorbol myristate acetate (PMA) also activated host PLD, while long-term treatment with PMA resulted in loss of the ability of L. monocytogenes to activate host PLD, suggesting an involvement of protein kinase C (PKC) in the activation of PLD. Rottlerin, an inhibitor of PKC delta in J774 cells, also inhibited the activation of PLD, but hispidin, an inhibitor of PKC betaI and betaII, did not. Pretreatment of J774 cells with the PLD inhibitor, 2, 3-diphosphoglycerate partially inhibited escape of the bacteria from the primary phagocytic vacuole.

Porcine 987P glycolipid receptors on intestinal brush borders and their cognate bacterial ligands.

Certain strains of enterotoxigenic Escherichia coli adhere to piglet intestinal epithelial cells by means of the 987P fimbriae. The 987P fimbrial structure consists of a helical arrangement of three fimbrial proteins, namely, the major subunit FasA and two minor subunits, FasF and FasG. FasG, which is located at the fimbrial tip and at various positions along the fimbriae, mediates 987P binding to glycoprotein receptors. In this study, we isolated and analyzed the structure of piglet glycolipid brush border receptors and characterized their cognate ligands on the 987P fimbriae. Two major glycolipid bands recognized by 987P fimbrial probes in thin-layer chromatography overlay assays were further purified by high-performance thin-layer chromatography and shown to comigrate with control galactosylceramide containing hydroxylated fatty acids and with sulfatide. Their structures were confirmed by fast atom bombardment mass spectrometry, which detected homologous series of ceramide monohexoside and sulfatide with hydroxylated fatty acyl chains ranging from h16:0 to h24:0. Assembled 987P fimbriae, pre- and postassembly dissociated fimbrial subunits, and Fab fragments of specific anti-FasG, -FasF, and -FasA were used to inhibit 987P-mediated bacterial binding to the two identified piglet glycolipids and corresponding isoreceptor controls. Only assembled fimbriae and anti-FasG Fab fragments were significantly able to inhibit bacterial binding to sulfatide, indicating that in addition to glycoproteins, FasG recognizes a specific glycolipid of piglet brush borders. In contrast, only anti-FasA Fab fragments were significantly able to inhibit bacterial binding to galactosylceramide with hydroxylated fatty acids and piglet hydroxylated ceramide monohexoside, indicating that FasA may determine a third type of ligand-receptor interaction in the piglet intestines. Since these bacterial adhesins recognize their respective glycolipid receptors only after being assembled in their final fimbrial quaternary structure, adhesin binding may involve cooperative interactions and the subunits by themselves may have very low binding affinities. Alternatively, conformation-sensitive domains of these subunits present in the assembled fimbriae may be required for glycolipid binding.

The two distinct phospholipases C of Listeria monocytogenes have overlapping roles in escape from a vacuole and cell-to-cell spread.

Listeria monocytogenes secretes two distinct phospholipases C, a phosphatidylinositol-specific phospholipase C (PI-PLC) and a broad-range phospholipase C (PC-PLC). In this study, single in-frame deletion mutants with mutations in each PLC and a double mutant lacking both PLCs were characterized with regard to virulence in mice, escape from a primary vacuole, and cell-to-cell spread in cell culture. The mutant lacking PI-PLC, previously shown to be twofold less virulent than the wild type in mice, had a minor defect in escape from a primary vacuole but was not notably affected in cell-to-cell spread. The mutant lacking PC-PLC was 20-fold less virulent in mice and was defective in cell-to-cell spread but had no measurable defect in escape from a primary vacuole. The mutant lacking both PLCs was 500-fold less virulent in mice and was severely diminished in its ability to escape from the primary vacuole and to spread cell to cell. Cellular levels of diacylglycerol and ceramide, products of PLC activity, accumulated beginning 3 to 4 h after infection of cells with wild-type bacteria. The bacterial PLCs were partially responsible for this activity, since cells infected with the mutant lacking both PLCs had a reduced increase in diacylglycerol and no increase in ceramide. Elevation of diacylglycerol in the absence of bacterial PLCs indicated that host cell phospholipase(s) was activated during infection. The results of this study were consistent with the two bacterial PLCs having overlapping functions throughout the course of intracellular infection. Furthermore, the PC-PLC, and possibly PI-PLC, appeared to be enzymatically active intracellularly.

Isolation and characterization of new phosphatidylglycerol acetals of plasmalogens. A family of ether lipids in clostridia.

A new phosphatidylglycerol acetal of cardiolipin plasmalogen has been isolated from Clostridium innocuum. The structure was derived from the results of quantitative group analyses, the identification of the products of acid hydrolysis, alkaline methanolysis, hydrolysis by a cardiolipin-specific phospholipase D and by one- and two-dimensional proton NMR. Two other minor ether phospholipids: the lyso form of the phosphatidylglycerol acetal of cardiolipin plasmalogen, and the phosphatidylglycerol acetal of plasmenylglycerol have been identified in C. innocuum lipid extracts.

Novel polar lipid composition of Clostridium innocuum as the basis for an assessment of its taxonomic status.

The extractable polar lipids of Clostridium innocuum have been shown to consist of glycosyldiradylglycerols, phospholipids and phosphoglycolipids. The major glycosyldiradylglycerols are D-Glcp(alpha 1-3)radyl2Gro and D-Galp(alpha 1-2)D-Glcp(alpha 1-3)radyl2Gro. Both glycolipids have some 1-O-(alk-1-enyl)-2-O-acyl species, in addition to diacyl species. The phospholipids include bisphosphatidylglycerol (cardiolipin), lysocardiolipin and phosphatidylglycerol (PG). In addition, several novel lipids have been found, including a PG acetal of cardiolipin plasmalogen, smaller amounts of a lyso form of this lipid, a PG acetal of PG plasmalogen, and two phosphoglycolipids, which represent 65% of total polar lipids. The latter have been identified as 2'-amino-1',3'- dihydroxypropane-3'-P-6-D-Galp(alpha 1-2)D-Glcp(alpha 1-3)radyl2Gro and a derivative of this lipid containing an acyl chain esterified to O-6 of the glucopyranosyl ring. Based on rRNA sequence data, C. innocuum is considered to be a relative of the mycoplasmas. Its unique lipid composition permits an assessment of the taxonomic status of C. innocuum, since the lipid amphiphiles display marked differences from those of Acholeplasma laidlawii.

Nonspecific phospholipase C of Listeria monocytogenes: activity on phospholipids in Triton X-100-mixed micelles and in biological membranes.

Listeria monocytogenes secretes a phospholipase C (PLC) which has 39% amino acid sequence identity with the broad-specificity PLC from Bacillus cereus. Recent work indicates that the L. monocytogenes enzyme plays a role during infections of mammalian cells (J.-A. Vazquez-Boland, C. Kocks, S. Dramsi, H. Ohayon, C. Geoffroy, J. Mengaud, and P. Cossart, Infect. Immun. 60:219-230, 1992). The homogeneous enzyme has a specific activity of 230 mumol/min/mg when phosphatidylcholine (PC) is dispersed in sodium deoxycholate. With phospholipid-Triton X-100 mixed micelles, the enzyme had a broad pH optimum between 5.5 and 8.0, and the rates of lipid hydrolysis were in the following order: PC > phosphatidylethanolamine (PE) > phosphatidylserine > sphingomyelin >> phosphatidylinositol (PI). Activity on PC was stimulated 35% by 0.5 M NaCl and 60% by 0.05 mM ZnSO4. When Escherichia coli phospholipids were dispersed in Triton X-100, PE and phosphatidylglycerol, but not cardiolipin, were hydrolyzed. The enzyme was active on all phospholipids of vesiculated human erythrocytes including PI, which was rapidly hydrolyzed at pH 7.0. PI was also hydrolyzed in PI-PC-cholesterol liposomes by the nonspecific PLC from L. monocytogenes and by the homologous enzyme from B. cereus. The water-soluble hydrolysis product was identified as inositol-1-phosphate. For the hydrolysis of human erythrocyte ghost phospholipids, a broad pH optimum was also observed. 32P-labelled Clostridium butyricum protoplasts, which are rich in ether lipids, were treated with PLC. The enzyme hydrolyzed the plasmalogen form of PE, its glycerol acetal, and cardiolipin, in addition to PE. I-, Cl- and F- stimulated activity on either PC- Triton X-100 mixed micelles or human erythrocyte ghosts, unlike the enzyme from B. cereus which is strongly inhibited by halides. Tris-HCl, phosphate, and calcium nitrate had similar inhibitory effects on the enzyme on the enzymes from L. monocytogenes and B. cereus.

Replacement of the aliphatic chains of Clostridium acetobutylicum by exogenous fatty acids: regulation of phospholipid and glycolipid composition.

The membrane lipid aliphatic chains of Clostridium acetobutylicum ATCC 4259 have been extensively modified by growth in biotin-free medium containing vitamin-free casein hydrolysate supplemented with either elaidic acid, oleic acid, or mixtures of palmitic and oleic acids. Growth with elaidic acid resulted in polar lipids containing 88.6% 18:1 acyl chains and 94.5% 18:1 ether-linked chains. Growth with oleic acid resulted in comparable levels of enrichment of the lipids with 18:1 chains and C19 chains containing cyclopropane rings. When cells were grown with mixtures of palmitic and oleic acids, the ether-linked chains of the plasmalogens were greater than or equal to 64% 18:1 plus C19 chains containing cyclopropane rings at all ratios of oleic to palmitic acid in the medium. The acyl chains reflected the palmitic acid content of the medium more closely. Marked changes were observed in both phospholipid and glycosyldiglyceride compositions as the lipid acyl and ether-linked chains became more enriched with unsaturated and cyclopropane chains. The ratio of the glycerol acetal of plasmenylethanolamine to phosphatidylethanolamine increased, the ratio of cardiolipin to phosphatidylglycerol decreased, and the ratio of diglycosyldiglyceride to monoglycosyldiglyceride increased. However, the monoglycosyldiglyceride/diglycosyldiglyceride ratio was lower for cells grown on 100% oleic acid than for cells grown on 60 or 80% oleic acid. In the membranes of cells grown on 100% oleic acid, the ratio of glycolipids to phospholipids was lower than that found in cells grown on 60% oleic acid. These results indicate that C. acetobutylicum regulates its polar lipid composition in a complex manner involving phospholipids and glycosyldiglycerides. These changes can affect the equilibria between those lipids that form bilayers and those lipids that tend to form nonlamellar phases when enriched with unsaturated aliphatic chains. Phosphoglycolipids of unknown structure were also observed in cells grown either with biotin or with fatty acids. The content of the most abundant phosphoglycolipid also varied with the degree of unsaturation of the cellular lipids.

Isolation and characterization of a novel four-chain ether lipid from Clostridium butyricum: the phosphatidylglycerol acetal of plasmenylethanolamine.

We describe the isolation and characterization of a novel four-chain ether phospholipid in Clostridium butyricum grown on petroselinic acid in the absence of biotin. The results of quantitative analyses of hydrolytic products, selective hydrolysis by mild acid or phospholipase C, 1H-, 13C-, and 31P-NMR, and fast atom bombardment-mass spectroscopy (FABMS) have resulted in the determination of the structure of this lipid as a phosphatidylglycerol acetal of plasmenylethanolamine. Smaller amounts of this lipid have been found in cells grown under similar conditions in the presence of oleic, cis-vaccenic, elaidic or dihydrosterculic acids. It also appears to be present in small amounts in cells grown with biotin. This lipid is structurally related to the more plentiful glycerol acetal of plasmenylethanolamine found in these cells.

Lipid shape as a determinant of lipid composition in Clostridium butyricum. The effects of incorporation of various fatty acids on the ratios of the major ether lipids.

The lipid composition of Clostridium butyricum is strongly influenced by the aliphatic chain compositions of the membrane lipids. Growth on cis-monounsaturated fatty acids in the absence of biotin was shown to affect the relative proportions of phosphatidylethanolamine, plasmenylethanolamine, and the glycerol acetal of plasmenylethanolamine most strongly, with smaller effects on the acidic lipids, phosphatidylglycerol and cardiolipin. The ratio of the glycerol acetal of plasmenylethanolamine to total phosphatidylethanolamine in cells grown on a series of fatty acids is shown to decrease in the following order; cis-vaccenic acid greater than or equal to oleic acid = C19-cyclopropane fatty acid greater than linoleic acid greater than petroselinic acid greater than elaidic acid greater than 14-methylhexadecanoic acid (anteiso-C17) greater than 12-methyltridecanoic acid (iso-C14). All fatty acids were extensively incorporated into the lipid acyl, alkenyl, and alkyl chains. There was considerable chain-elongation of the iso-C14 to iso-C16. The results are consistent with the hypothesis that the membrane lipid composition is strongly influenced by lipid shape and that the observed changes in lipid composition serve to stabilize the bilayer arrangement of the cell membrane.

Deuterium nuclear magnetic resonance studies on the plasmalogens and the glycerol acetals of plasmalogens of Clostridium butyricum and Clostridium beijerinckii.

Deuterium nuclear magnetic resonance was used to investigate the structure of different lipid fractions isolated from the anaerobic bacteria Clostridium butyricum and Clostridium beijerinckii. The fractions isolated from C. butyricum were (1) phosphatidylethanolamine/plasmenylethanolamine and (2) the glycerol acetal of plasmenylethanolamine, and from C. beijerinckii similar fractions containing principally (1) phosphatidyl-N-monomethylethanolamine, along with its plasmalogen, and (2) the glycerol acetal of this plasmalogen were isolated. The third fraction from both species consisted largely of the acidic lipids phosphatidylglycerol and cardiolipin along with plasmalogen forms of these lipids. Palmitic acid with deuterium labels at C-2, C-3, or C-4 or oleic acid with deuterium labels at C-2 and C-9,10 was added to the growth medium and incorporated to various extents in the lipid fractions. Biochemical analysis showed that palmitic acid and oleic acid were preferentially bound to the sn-2 and sn-1 positions, respectively, of the glycerol backbone when both fatty acids were added to the medium. From the 2H NMR spectra, the hydrocarbon chain ordering near the lipid-water interface could be determined and appeared to be similar for all three lipid fractions. The deuterium quadrupole splitting and order parameter were low at the C-2 segment and increased by almost a factor of 2 at positions C-3 and C-4 for cells fed with deuterated palmitic acid along with unlabeled oleic acid. These results agree with previous findings on pure diacyl lipids in which the sn-2 chain was found to adopt a bent conformation at the carbon segment C-2. However, two unusual quadrupole splittings could be detected for the plasmalogens.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of bilayer stability in Clostridium butyricum: studies on the polymorphic phase behavior of the ether lipids.

Three of the major phospholipids of the cell membrane of Clostridium butyricum are phosphatidylethanolamine (PE), plasmenylethanolamine (PlaE), and the glycerol acetal of plasmenylethanolamine. When cultured in the absence of biotin in media supplemented with a cis-unsaturated fatty acid, the cellular lipids become highly enriched with the fed fatty acid. Under these conditions, the ratio of the glycerol acetal of PlaE to the sum of PE plus PlaE increases markedly over that seen in cells containing mixtures of saturated and unsaturated fatty acids [Johnston, N.C., & Goldfine, H. (1985) Biochim. Biophys. Acta 813, 10-18]. We have studied the polymorphic phase behavior of the phospholipids from C. butyricum grown on oleic acid using differential scanning calorimetry, 31P nuclear magnetic resonance, and X-ray diffraction. The mixed PE plus PlaE fraction undergoes a transition from the gel to liquid-crystalline state at -1.9 degrees C and a lamellar to reversed hexagonal (L----H) transition at or near 0 degrees C. The glycerol acetal of PlaE melts at 16.1 degrees C, and as predicted from lipid packing theory, the lamellar phase is stabilized, up to 50 degrees C. Addition of the oleate-enriched glycerol acetal of PlaE to dioleoylphosphatidylethanolamine, or the PE plus PlaE fraction from oleate-grown cells, stabilized the lamellar arrangement of the mixtures. A ratio of glycerol acetal of PlaE to total PE (PE plus PlaE) of 0.5, which is close to that found in cells grown on palmitic plus oleic acid, 0.6-0.7, did not produce a lamellar phase at 37 degrees C when the lipids enriched with oleic acid were tested,(ABSTRACT TRUNCATED AT 250 WORDS)

2H-NMR studies on ether lipid-rich bacterial membranes: deuterium order profile of Clostridium butyricum.

Palmitic acid specifically deuterated at different carbon atoms, has been incorporated biosynthetically into the membrane lipids of Clostridium butyricum. The lipids of this organism are rich in plasmalogens and their glycerol acetals and exhibit an unusual fatty acyl and alkenyl chain distribution with saturated chains mainly at the sn-2 position and unsaturated chains at the sn-1 position. The ordering of the deuterated hydrocarbon chains in whole cells was measured with deuterium nuclear magnetic resonance and was compared to the order profiles of isolated cell membranes and membranes formed from the total phospholipid extract. The shape of the order profiles was similar for all three membranes, but the absolute values of the order profiles in whole cells and isolated membranes were lower than those of the liposomal lipids. The order profiles have the same characteristic shape as those found for the lamellar liquid-crystalline phases of synthetic diacylphospholipids.

Phospholipid aliphatic chain composition modulates lipid class composition, but not lipid asymmetry in Clostridium butyricum.

The phospholipid composition of the butyric acid-producing clostridia is responsive to the degree of enrichment of the lipids with cis-unsaturated fatty acids. When Clostridium butyricum and Clostridium beijerinckii are grown on oleic acid in media devoid of biotin, the acyl and alk-1-enyl chains of the phospholipids become highly enriched with 18:1 and C19-cyclopropane. Under these conditions there is a marked increase in the glycerol acetals of the major plasmalogens of these organisms. We have grown both species on mixtures of palmitate and oleate in the absence of biotin. The alk-1-enyl chains were highly enriched with C18-unsaturated and C19-cyclopropane residues at all but the highest ratios of palmitate to oleate (80:20, w/w) added to the medium. At ratios of palmitate to oleate greater than or equal to 40:60, the saturated acid was incorporated predominantly into the phospholipid acyl chains in both organisms. The effects of increasing unsaturation of the acyl chains as the ratio of oleate to palmitate was increased was examined in C. butyricum. In cells grown on mixtures of palmitate and oleate equal to or exceeding 40% palmitate, the ratio of glycerol acetal lipid to total phosphatidylethanolamine (PE) was relatively constant. As the proportion of oleic acid added to the medium was increased, the ratio of glycerol acetal lipid to PE increased from 0.7 to 2.0. Thus the ratio of the polar lipids appears to respond to the content of phospholipids that contain two unsaturated chains. The fraction of PE present as plasmalogen remained relatively stable (0.82 +/- 0.05) at varying ratios of medium oleic and palmitic acids. Both the glycerol acetal of ethanolamine plasmalogen, and ethanolamine plasmalogen, are shown to be 80% or more in the outer monolayer of the cell membrane. These two polar lipids represent approx. 50% of the phospholipids in cells grown on exogenous fatty acid. The bulk of the remainder is polyglycerol phosphatides. We suggest that the ability of both species to grow with highly unsaturated membranes is related to their ability to modulate their polar lipid composition.

Lipid composition in the classification of the butyric acid-producing clostridia.

An examination of 20 strains of butyric acid-producing Clostridium species for phospholipid class compositions, plasmalogen content, and acyl and alk-l-enyl chains showed that the deoxyribonucleic acid homology groups I (Clostridium butyricum) and II (Clostridium beijerinckii) could be distinguished by their lipid compositions. The phospholipids of C. butyricum strains had ethanolamine as the major nitrogenous lipid polar head-group moiety, more octadecenoate plus C19-cyclopropane than hexadecenoate plus C17-cyclopropane acyl chains, and the predominant alk-l-enyl chain was C18-monounsaturated. Clostridium beijerinckii strains had N-methylethanolamine plus ethanolamine in phospholipid head-groups, more hexadecenoate plus C17-cyclopropane than octadecenoate plus C19-cyclopropane acyl chains, and the major alk-l-enyl chain was C16-saturated. Three species falling outside the two homology groups Clostridium fallax, Clostridium pseudofallax and Clostridium acetobutylicum had ethanolamine as the major phospholipid base, but these species could be distinguished from C. butyricum by their acyl and alk-l-enyl chain compositions. The lipid composition of Clostridium pasteurianum is even more distinct.

Effects of growth temperature on fatty acid and alk-1-enyl group compositions of Veillonella parvula and Megasphaera elsdenii phospholipids.

Veillonella parvula ATCC 10790, an anaerobic gram-negative coccus, contains diacyl and alk-1-enyl acyl (plasmalogen) forms of phosphatidylethanolamine and phosphatidylserine. We studied the effect of growth temperature on the lipid composition of this strain. There was a small increase in the phosphatidylethanolamine content but no change in the content of plasmalogens at the lower growth temperatures tested. The total acyl chains and the plasmalogen acyl chains contained between 73 and 80% mono-unsaturated fatty acids at all growth temperatures. The plasmalogen alk-1-enyl chains were significantly more unsaturated in cells grown at 30 and 25 degrees C than in cells grown at 37 degrees C. Differential scanning calorimetry of the hydrated phospholipids showed lower phase transition temperatures for the lipids from the cells grown at the lower temperatures. In Megasphaera elsdenii lipids, which are similar in composition to the lipids of V. parvula, the proportion of phosphatidylethanolamine also increased slightly at lower growth temperatures, with no significant change in the content of plasmalogens. M. elsdenii contained cyclopropane fatty acyl and alk-1-enyl chains in addition to the mono-unsaturated and saturated chains previously reported. As cells entered the stationary phase of growth at 30 and 42.5 degrees C, there was a reciprocal increase in the proportion of cyclopropane acyl chains and decrease in the unsaturated moieties. The total proportion of cyclopropane and unsaturated acyl and alk-1-enyl chains was more than 65% at all growth temperatures studied, and there was no discernible increase in the sum of these moieties at the lower growth temperatures.

Phase behavior of ether lipids from Clostridium butyricum.

Ether lipids have been isolated from the phospholipid fraction of Clostridium butyricum IFO 3852 cells which had been grown in media devoid of biotin with added elaidic acid or oleic acid. The plasmalogen form of phosphatidylethanolamine (plasmenylethanolamine) from elaidate-grown cells was highly enriched with 18:1 in both the alk-1-enyl and acyl chains. A transition from the gel to liquid-crystalline state, with a peak maximum (Tm) at 33 degrees C and enthalpy delta H = 5.7 kcal/mol, was observed by differential scanning calorimetry. With the fluorescent probes cis- and trans-parinaric acids, transitions were observed at 33 degrees C on heating and at 29 degrees C on cooling. These transition temperatures are 5-6 degrees C lower than those reported for the corresponding diacyl lipid, dielaidoylphosphatidylethanolamine. A similar study of the phase behavior of both the elaidate-enriched and oleate-enriched glycerol acetal derivative of plasmenylethanolamine from C. butyricum revealed a large hysteresis of 12.5-16 degrees C. Hysteresis in the polar head group motion was also observed by 31P nuclear magnetic resonance. The elaidate-enriched lipid, which melted between 28 and 33 degrees C, appears to undergo supercooling prior to the transition to the gel state at about 18-13 degrees C, depending on the scanning rate. The formation of a more ordered gel state relative to plasmenylethanolamine was indicated by a 2-fold increase in delta H. Electron microscopy revealed a marked reorganization from typical multilamellar liposomes above Tm to large needle-like structures below Tm. The oleate-enriched glycerol acetal lipid formed the gel phase at -4 degrees C, which is 10 degrees C above the transition temperature reported for dioleoylphosphatidylethanolamine. Stabilization of oleate-enriched glycerol acetal lipid bilayers may result from hydrogen bonding between polar head groups. The relationship of the phase behavior of the ether lipids to the lipid composition and phase behavior of C. butyricum membranes is discussed.

Novel fatty acids from the royal jelly of honeybees (Apis mellifera, L.).

Three new compounds isolated from the royal jelly of honeybees (Apis mellifera, L.) have been identified as 8-hydroxyoctanoic acid, 3-hydroxydecanoic acid and a dextrorotatory isomer of 3,10-dihydroxydecanoic acid.