Glycolipids of mycobacteria and related microorganisms

A Review on Mycobacteriophages: From Classification to Applications

Mycobacterial infections are a group of life-threatening conditions triggered by fast- or slow-growing mycobacteria. Some mycobacteria, such as Mycobacterium tuberculosis, promote the deaths of millions of lives throughout the world annually. The control of mycobacterial infections is influenced by the challenges faced in the diagnosis of these bacteria and the capability of these pathogens to develop resistance against common antibiotics. Detection of mycobacterial infections is always demanding due to the intracellular nature of these pathogens that, along with the lipid-enriched structure of the cell wall, complicates the access to the internal contents of mycobacterial cells. Moreover, recent studies depicted that more than 20% of M. tuberculosis (Mtb) infections are multi-drug resistant (MDR), and only 50% of positive MDR-Mtb cases are responsive to standard treatments. Similarly, the susceptibility of nontuberculosis mycobacteria (NTM) to first-line tuberculosis antibiotics has also declined in recent years. Exploiting mycobacteriophages as viruses that infect mycobacteria has significantly accelerated the diagnosis and treatment of mycobacterial infections. This is because mycobacteriophages, regardless of their cycle type (temperate/lytic), can tackle barriers in the mycobacterial cell wall and make the infected bacteria replicate phage DNA along with their DNA. Although the infectivity of the majority of discovered mycobacteriophages has been evaluated in non-pathogenic M. smegmatis, more research is still ongoing to find mycobacteriophages specific to pathogenic mycobacteria, such as phage DS6A, which has been shown to be able to infect members of the M. tuberculosis complex. Accordingly, this review aimed to introduce some potential mycobacteriophages in the research, specifically those that are infective to the three troublesome mycobacteria, M. tuberculosis, M. avium subsp. paratuberculosis (MAP), and M. abscessus, highlighting their theranostic applications in medicine.

Mono- and dialdehyde of trehalose: new synthons to prepare trehalose bio-conjugates

Trehalose, a non-reducing disaccharide of glucose, is a natural bioactive and non-toxic sugar. It is found in many organisms that synthesise it when their cells are exposed to stress conditions. While not produced by mammalian cells, this disaccharide and also some of its derivatives have been shown to have a number of interesting properties that indicate their importance in the treatment of certain human diseases. Differentiating the two glucosyl moieties in the trehalose molecule has often been a synthetic challenge. We report here an easy way to obtain the monoaldehyde of trehalose, as well as the relevant symmetrical dialdehyde. The reactivity of the aldehyde functionalities involved in the molecular structure of these synthons allows the easy preparation of the corresponding amino or carboxy derivatives of trehalose, as well the synthesis of some new trehalose conjugates useful for diagnostic or therapeutic purposes.

Characterization of the Rothia spp. and their role in human clinical infections

The genus Rothia are emerging as opportunistic pathogens associated with various infections in immunocompromised and immunocompetent individuals. This review describes the taxonomy, cell wall structure, pathogenesis, phenotypic and molecular characteristics, clinical diseases, treatment and, as well as, the related genera that may be misidentified by Rothia species.

Synthesis of trehalose glycolipids

Chemical synthesis of trehalose glycolipids such as DAT, TDM, SL-1, SL-3, and Ac₂SGL from MTb, emmyguyacins from fungi, succinoyl trehalose from rhodococcus, and maradolipids from worms, as well as mycobacterial oligosaccharides is reviewed.

Structure and function of glycoglycerolipids in plants and bacteria

Phosphoglycerolipids are abundant membrane constituents in prokaryotic and eukaryotic cells. However, glycoglycerolipids are the predominant lipids in chloroplasts of plants and eukaryotic algae and in cyanobacteria. Membrane composition in chloroplasts and cyanobacteria is highly conserved, with monogalactosyldiacylglycerol (MGD) and digalactosyldiacylglycerol (DGD) representing the most abundant lipids. The genes encoding enzymes of galactolipid biosynthesis have been isolated from Arabidopsis. Galactolipids are crucial for growth under normal and phosphate limiting conditions. Furthermore, they are indispensable for maximal efficiency of photosynthesis. A wide variety of glycoglycerolipids is found in different bacteria. These lipids contain glucose or galactose, in some cases also mannose or other sugars with different glycosidic linkages in their head group. Some bacterial species produce unusual glycoglycerolipids, such as glycophospholipids or glycoglycerolipids carrying sugar head groups esterified with acyl residues. A number of genes coding for bacterial glycoglycerolipid synthases have been cloned and the enzymes characterized. In contrast to the breadth of information available on their structural diversity, much less is known about functional aspects of bacterial glycoglycerolipids. In some bacteria, glycoglycerolipids are required for membrane bilayer stability, they serve as precursors for the formation of complex membrane components, or they are crucial to support anoxygenic photosynthesis or growth during phosphate deficiency.

Synthesis of alkyl [(alkyl 6-deoxy-alpha-D-gluco-heptopyranosyl- uronate) 6-deoxy-alpha-D-gluco-heptopyranosid]uronates, a novel type of mirror pseudo cord factor

The 1-octyl, 1-pentadecyl, 1-hexadecyl, 1-heptadecyl, and 1-octadecyl diesters of (6-deoxy-alpha-D-gluco-heptopyranosyluronic acid) 6-deoxy-alpha-D-gluco-heptopyranosiduronic acid, a new homolog of trehalosuronic acid, were prepared by two procedures. One procedure involved conversion of the peracetylated acid into its dichloride, reaction of the latter with the alkanols, and acid-catalyzed deacetylation of the products, whereas the other consisted of reaction of alkyl mesylates with the potassium salt of the unprotected acid.

Molecular species of mycolic acid subclasses in eight strains of Mycobacterium smegmatis

Thin layer chromatographic and gas chromatographic separation and mass spectrometric identification of mycolic acid subclasses and molecular species from eight strains of Mycobacterium smegmatis were established. Two major adjacent spots and a lower minor one were detected on silica gel thin layer chromatograms of methyl esters. The most abundant subclass showing the highest Rf value on TLC was that of alpha-mycolic acids (M1), the second was that of alpha-mycolic acids (M1), a shorter homologue than alpha-mycolates, and the third was the hydroxy mycolic acids (M4) derived from epoxy mycolic acids. They were identified by gas chromatography-mass spectrometry as their trimethylsilylether derivatives. alpha'-Mycolic acids were monoenoic acids ranging from C60 to C66 and possessing an alpha-unit of C24:0. Such profiles of alpha'-mycolic acids were common in eight strains. alpha-Mycolates were dienoic acids ranging from C75 to C79 and possessing an alpha-unit of C24:0. In most strains, the major molecular species of alpha-mycolates were odd-carbon-numbered, centering at C77 and C79, possessing a methyl branch in the even-carbon-numbered straight chain. The average carbon number of alpha-mycolates, from seven strains examined, was about 78, but that of the Takeo strain was 76.3. The profiles of epoxy mycolic acid molecular species composition from eight strains ranging from C75 to C81 were very similar to their M1 subclass profiles.

Determination of molecular species composition of C80 or longer-chain alpha-mycolic acids in Mycobacterium spp. by gas chromatography-mass spectrometry and mass chromatography

The molecular species composition of alpha-mycolic acids ranging from C68 to C86 in 13 rapidly growing and 12 slowly growing mycobacterial species was determined by gas chromatography, gas chromatography-mass spectrometry, and mass chromatography. In gas chromatographic analysis, the molecular species of alpha-mycolic acids were well separated as trimethylsilyl ether derivatives of the methyl esters, according to their total carbon numbers. The total carbon and double-bond numbers of mycolic acids at each peak on gas chromatograms were determined from the [M]+, [M - 15]+, and [M - 90]+ ions on the mass spectrum, and straight and branched chain structures were identified by the mass fragment ions [A]+, due to C2--C3 cleavage [R-CH-O-Si(CH3)3]+, and [B]+, due to C3--C4 cleavage [(CH3)3-Si-O-CH-CH(R')-COOCH3]+. The concentration of odd- and even-carbon-numbered mycolic acids, which often overlap each other on gas chromatograms, and the composition of three homologous mycolic acids with different alpha units (C22:0, C24:0, and C26:0) were clearly determined by mass chromatography monitoring [M - 15]+ ions and [B - 29]+ ions, respectively. The molecular species composition of alpha-mycolic acids and their average carbon numbers (av. cn.) as a simple expression of the composition were calculated from the mass chromatograms. Each mycobacterial species examined was demonstrated to possess a characteristic profile of alpha-mycolic acid composition, and based on this the species were classified approximately into eight groups: C68 to C76 (av. cn. 72), dienoic, possessing a C20 alkyl branch at the 2 position (C22 alpha-unit) for Mycobacterium diernhoferi and Mycobacterium sp. strain 3707, a chromogenic rapid grower; C72 to C78 (av. cn. 75), dienoic with both C22 and C24 alpha units, containing a small or a large amount of odd-carbon-numbered molecules, for M. vaccae, M. rhodesiae, and M. phlei (chromogenic rapid growers); C72 to C80 (av. cn. 75 to 77), dienoic with C24 alpha-unit, containing a moderate or a large amount of odd-carbon-numbered molecules, for M. smegmatis, M. chitae, M. chelonae (M. chelonei), and M. fortuitum (nonchromogenic rapid growers); C78 to C82 (av. cn. 80), even-carbon-numbered dienoic with C24 alpha unit for M. agri and M. thermoresistible (rapid growers); C75 to C81 (av. cn. 77 to 79), odd-carbon-numbered dienoic with C24 alpha unit for M. nonchromogenicum complex (M. nonchromogenicum, M. terrae, and "M. novum") (slow growers); (vi) C76 to C84 (av. cn. 79 to 81), even-carbon-numbered dienoic with C24 alpha unit for MAIS complex including M. scrofulaceum, M. avium, and M. intracellulare (slow growers); (vii) C72 to C80 (av. cn. 77 to 79), even-carbon-numbered dienoic with C24 alpha unit for M. szulgai, M. gordonae, and M. kansasii (chromogenic slow growers); and (viii) C76 to C86 (av. cn. 79 to 81), even-carbon-numbered dienoic with C26 alpha unit M. bovis Ravenol and BCG and M. tuberculosis H37Rv. This study demonstrated that gas chromatography-mass spectrometric analysis of the molecular species composition of alpha-mycolic acid can give rapid, important, and very precise information for the identification of pathogenic and nonpathogenic mycobacterial species.

Chemical composition of antigen 60 from Mycobacterium bovis BCG

Antigen 60 (A60), the main thermostable immunogen of tuberculin and PPD, has been purified from Mycobacterium bovis BCG cytoplasm, and identified by crossed immunoelectrophoresis with anti-BCG polyclonal antiserum. Two A60 fractions, free lipids and lipid-conjugated compounds, have been recognized. The free lipids represented about 30% (dry weight), and consisted essentially of C16-C18 fatty acids, and of phosphatidyl-inositol-mannosides. Lipoconjugates, upon DEAE-cellulose chromatography and gel filtration, yielded two main fractions of neutral and polar components. Chromatography of delipidated and deproteinized A60 on Sephadex G-100 yielded: a high molecular weight fraction (Al, 18%, a lipoglucan of congruent to 10(6)), and a low molecular weight fraction (B, 10%, a lipopeptidoglycan of congruent to 10(4)) containing mannose, glucose, and small amounts of arabinose. The polysaccharide moieties of fractions Al and B were submitted to acetylation, methylation, and acid hydrolysis, and the structure of the hydrolysed polymer was deduced by combined gas chromatography/mass spectrometry analysis. The results indicated a branched structure involving 1,4-, 1,6-, and 1,4,6-linked D-gluco- or D-manno-pyranosyl residues. Glucan- and peptidoglycan-bound fatty acids were identified as saturated (C16-C18) and monounsaturated linear acids (C12-C18). Immunodiffusion on agarose gel indicated that delipidation and proteolysis did not suppress the ability of A60 to yield immunoprecipitates with anti-A60 antiserum. The high polymer fractions obtained by chromatography on DEAE cellulose and Sephadex G-100 were also reactive. It is concluded that A60 is made of free lipids and of lipopeptidoglycans of high molecular weights (10(6)-10(7)) endowed with immunogenic properties.

Haptenic oligosaccharides in antigenic variants of mycobacterial C-mycosides antagonize lipid receptor activity for mycobacteriophage D4 by masking a methylated rhamnose

The simple apolar C-mycosides, i.e., structurally well-defined hydrophobic glycopeptidolipids of several Mycobacterium species (see diagram below), were earlier shown to behave as receptors for adsorption of mycobacteriophage D4. This phage is usually virulent for Mycobacterium smegmatis. More complex, polar C-mycosides with additional carbohydrate substituents attached solely to the deoxytalose have recently been described. They are the highly specific serotyping antigens discovered by W. B. Schaefer--lipids which characterize members of the Mycobacterium avium-Mycobacterium intracellulare-Mycobacterium scrofulaceum (MAIS) complex. Both kinds are depicted in the structure below: (Formula: see text) where X equals H (for simple, apolar C-mycosides) and X equals small oligosaccharides (for antigenic forms; more complex, polar C-mycosides). The present investigations showed that the purified polar antigenic lipids exhibit considerably less adsorptive activity for D4 than do the apolar C-mycosides. Thus, the haptenic oligosaccharides are believed to shield the site in the molecule that the phage recognizes, and the blocking is reinforced by the specific antibodies that the antigens elicit. Although the MAIS serovars usually also produce the phage-reactive apolar C-mycosides, they are not permissive hosts for D4, nor do whole cells adsorb the phage. We suggest that in these species the apolar forms are probably "covered" at the cell surface by the antigenic lipids. Therefore, these antigenic mycosides may play a putative role in virulence of the MAIS members by protecting these mycobacteria from their own potential pathogen. The results of chemical transformations at specific sites of the mycoside core coupled with studies of simple synthetic lipid glycosides indicated that the principal phage receptor activity resides in the terminal methylated rhamnose (see diagram). It is this sugar which is evidently masked by the (seemingly remote) haptenic oligosaccharides.

Separation and analysis of novel polyunsaturated mycolic acids from a psychrophilic, acid-fast bacterium, Gordona aurantiaca

More than 30 molecular species of highly unsaturated mycolic acids, ranging from C60 to C78 and possessing between two and seven double bonds, have been obtained from a new genus of acid-fast bacteria, Gordona aurantiaca. They were fully separated and identified as their trimethylsilyl ether derivatives by a combination of silica gel thin-layer chromatography (TLC), argentation thin-layer chromatography and gas chromatography/mass spectrometry (GC/MS). On silica gel thin-layer chromatography two adjacent spots, corresponding to mycolic acids possessing different structures of straight-chain and alpha-alkyl branch, were detected. The lower spot was separated by argentation TLC into four subclasses: monoenoic (including a small amount of saturated), dienoic, trienoic and tetraenoic mycolic acids ranging from C62 to C74 and possessing a C16:0, C18:0 or C20:0 alkyl branch at the C-2 position. The upper spot was separated by argentation TLC into five subclasses: dienoic (including a small amount of monoenoic), trienoic, tetraenoic, pentaenoic and hexaenoic (heptaenoic) acids ranging from C64 to C78 and possessing a C18:1 or C20:1 alkyl branch at the C-2 position. These types of mycolic acid structure differ from those reported previously in Mycobacteria and Nocardia, in the numbers of both carbon atoms and double-bonds and the intermediate length of the alpha-alkyl branch. The characteristic polyenoic structure of the straight-chain alkyl unit was also confirmed by GC/MS analysis of the meromycolaldehydes obtained after pyrolysis of the methyl mycolates. The major aldehydes obtained from the lower-spot mycolic acids were C44, C46, C48, C50 and C52, while those from the upper-spot mycolic acids were C48, C50, C52, C54 and C56, centering at C54. These aldehydes were also shown to possess between two and four double bonds in the lower-spot and between two and seven double bonds in the higher-spot mycolic acids, respectively. The physiological role of such highly polyunsaturated mycolic acids in psychrophilic acid-fast bacteria is discussed.

Mycolic acid composition and thermally adaptative changes in Nocardia asteroides

The nocardomycolic acid compositions of extractable and the cell wall-bound lipids from five strains of Nocardia asteroides (A-23007, A-23094, B-23006, B-23095, and IFO 3384) were compared by using gas chromatography-mass spectrometry. The molecular species composition of mycolic acid differed significantly among the strains of N. asteroides. The A-23007 strain possessed the shortest species, centering at C(44(46)), and the A-23094 and IFO-3384 strains followed, each centering at C(52). The B-23006 and B-23095 strains possessed the longest species, centering at C(56) or C(54), thus indicating that N. asteroides strains accommodate a heterogeneous group in respect to carbon numbers of mycolic acids. The doublebond isomers of mycolic acids from the representative strain IFO 3384 were fully separated and analyzed by argentation thin-layer chromatography, followed by gas chromatography-mass spectrometry. The reference strain (IFO 3384) possessed up to four double bonds on the straight chain of mycolic acids ranging from C(46) to C(60). All of the species possessed a C(14) alkyl branch at C-2. The more highly unsaturated subclasses consisted of the longer-chain mycolic acids. Marked changes in mycolic acid composition were induced by altering the growth temperature of strain IFO 3384. The cells grown at the higher temperature (50 degrees C) contained more saturated mycolic acids, whereas those grown at the lower temperature (17 degrees C) had more polyunsaturated (up to tetraenoic) mycolic acids, although a significant difference in carbon chain length was not detected. These changes in the degree of unsaturation of mycolic acids occurred shortly after shifting the growth temperature from 17 to 50 degrees C at logarithmic stages of the bacterial growth, thus indicating that N. asteroides can adapt to changes in the environmental temperature by altering the structure of mycolic acids of the cell walls.

Recent European research activities in mycobacteriology

The subject of mycobacteriology is becoming an increasingly popular and complex one and the contribution by European scientists has been considerable. The important areas of research include taxonomy and the improvement of identification methods; biochemistry, including enzymology, metabolic regulation, lipid chemistry, iron uptake and metabolism, pigment synthesis and DNA chemistry; genetics and bacteriophages; ecology, including the effect of contact with environmental mycobacteria on the mammalian immune response; immunology; and the association of disease and cell-wall-free mycobacteria and studies on the leprosy bacillus. The European Society of Mycobacteriologists has recently been founded to unite workers in these disciplines and to promote and disseminate knowledge in this subject.

Investigation of the component of Propionibacterium acnes (Corynebacterium parvum) responsible for macrophage activation

Mouse peritoneal macrophages, activated with Propionibacterium acnes (Corynebacterium parvum) in vivo, exhibited altered morphological characteristics, increased acid phosphatase activity, and release of [EH]thymidine-labeled DNA from tumor cells in vitro. Comparison with macrophages from mice injected with a control organism, P. jensenii, showed that the morphological changes, but not acid phosphatase, correlated with the development of tumoricidal activity. Investigation of the microbial component responsible for this activity indicated it was heat stable and refractory to extraction by methanol-chloroform, dilute acid, butanol, or a serial combination of extraction procedures. When the cells were disrupted by mechanical breakage, no activity could be found in the cell wall, soluble cytoplasm, or particulate cytoplasm. These results suggest that intact organisms are required for macrophage activation, and they may resolve conflicting reports on the nature of the immunostimulating activity of P. acnes.

Lipids of the Streptomycettes. Structural investigation and biological interrelation a review

During a systematic investigation of lipids of Streptomycetes a series of compounds of biochemical and microbiological interest have been isolated and characterized. These include several menaquinones, glycosyl diglycerides (glucuronosyl and isoladobinosym diglycerides), two ornithino lipids and a diol phospholipid. Some of these lipids were not known previously as constituents of streptomycete cells although they have been encountered elsewhere; others have proved to be novel lipids. The results of structural studies of these lipids are reviewed and some of their possible biological functions are discussed.

The polar lipids of group B Streptococci. I. Glucosylated diphosphatidylglycerol, a novel glycopholipid

1. From group B Streptococci a novel glycophospholipid was isolated, which contained D-glucose, glycerol, acyl groups and phosphorus in a molar ratio of approx. 1:3:4:2. It was established to be 2'-O-alpha-D-glucopyranosyl-, 1',3'-bis-(1,2-diacyl-sn-glycero-3-phospho)-glycerol. 2. The structure of the deacylated core was accomplished by analyses of the breakdown products obtained on (i) strong alkaline hydrolysis, (ii) Smith-degradation, and (iii) periodate oxidation with subsequent hydrazinolysis. The four acyl groups were located by sequential degradation of the native lipid with phospholipase A2 and 98% acetic acid. 2. In group B Streptococci approximately 25% of diphosphatidylglycerol occurs in the form of its glucosylated derivative which accounts for 18% of the lipid phosphorus. The glucosylated phosphatidylglycerol analogue could not be detected. A phosphoglucolipid, however, was present, which was tentatively identified as glycerophosphodiglucosyldiacylglycerol.

Biosynthesis of glycosyldiglycerides in Mycobacterium smegmatis

A particulate enzyme preparation from Mycobacterium smegmatis catalyzes the transfer of [(14)C]galactose from uridine 5'-diphosphate (UDP)-[(14)C]galactose and of [(14)C]glucose from UDP-[(14)C]glucose into chloroform-soluble products. The radioactive neutral lipids were purified by passage through diethylaminoethyl-cellulose, followed by thin-layer chromatography. When UDP-glucose was used as substrate, two major radioactive lipids were obtained; one had a hexose-glucose-glycerol ratio of 1:1:1. The second product had a hexose-glycerol ratio of 2:1 and, in addition to glucose, contained lesser amounts of mannose and galactose. With UDP-galactose as substrate, two radioactive products were observed that were chromatographically indistinguishable from the [(14)C]glucosyl-labeled mono- and diglycosyldiglyceride. Palmitate and oleate were the predominant fatty acid constituents in these lipids and were present in equimolar amounts in all of the products examined. The products have thus been identified as monoglycosyldiglyceride and a diglycosyldiglyceride containing glucose as the major hexose along with mannose and galactose. Properties of the galactosyl and glucosyl transferases are described.

Lipid composition of some species of Arthrobacter

The lipids from Arthrobacter crystallopoietes, A. pascens, and A. globiformis were investigated. Each strain contained three glycolipids, a monogalactosyl diglyceride, a digalactosyl diglyceride, and a dimannosyl diglyceride, and traces of triand tetraglycosyl diglycerides. The phospholipids in all three strains consisted of bisphosphatidylglycerol, phosphatidylglycerol, and phosphatidylmyoinositol. No evidence could be obtained for the occurrence of mannophosphoinositides. Analysis of the fatty acids by gas-liquid chromatography showed that they are predominantly C(15:0)anteiso and C(17:0)anteiso compounds. No significant differences were observed in the composition of lipids extracted from homogeneous cell preparations of the rod and sphere forms of A. crystallopoietes.

Wax D fraction of an unclassified Mycobacterium strain

Wax D prepared from the P-6 strain of the scotochromogenic species of Mycobacterium scrofulaceum constituted 0.3% of the dry bacilli. In the acid hydrolysates, alanine, glutamic acid, glycine, and mesodiaminopimelic acid were found as amino acid constituents. Mannose, galactose, and glucosamine were detected by paper chromatography. However, arabinose could not be detected. The quantity of hexosamine was 0.2 to 0.3%. Wax D of P-6 was found to be adjuvant-active, as revealed by a positive corneal reaction. The antigenicity of wax D of P-6 was shown by the agglutination reaction between the suspension of wax D and the anti-wax D antiserum. Periodate oxidation of the hydrosoluble portion reduced the inhibitory effect of the hydrosoluble portion on agglutination of the suspension of wax D. The light fraction of wax D had a peptide portion consisting of alanine, glutamic acid, glycine, and diaminopimelic acid and was found to be adjuvant-active in an amount of 1,000 mug.

Acute granulomatous response produced in mice by trehalose-6,6-dimycolate

Trehalose-6,6-dimycolate, a toxic lipid derived from tubercle bacilli, injected intravenously into mice in 10% emulsions of Bayol F caused a three- to fourfold increase in the weights of lungs compared with those of mice injected with emulsions of Bayol F alone or emulsions of Wax D. This change is due to a heavy infiltration of the lungs with granulocytes and large numbers of macrophages, with formation in some of the infiltrates of round foci, resembling granulomas.

Immunochemical analysis of serologically active lipids of Mycoplasma pneumoniae

The major complement-fixing antigen of Mycoplasma pneumoniae is found in the lipid fraction of the organism. When the lipids of M. pneumoniae were fractionated by column chromatography on silicic acid, serological activity against both rabbit and human immune sera was found in two fractions, B and D. Fraction B, eluted with chloroform-methanol (9:1), was a minor component in terms of total complement-fixing activity and contained a complex of lipids which were detected in the region characteristic of phosphatidic acids by thin-layer chromatography on Silica Gel G. Fraction D, eluted with ethyl acetate-methanol (3.5:2), had approximately the same complement-fixing antigen titer as the original lipid extract and appeared as a "comet-shaped" spot between phosphatidylethanolamine and phosphatidylcholine on Silica Gel G plates charred with sulfuric acid. However, by thin-layer chromatography on Silica Gel H impregnated with sodium tetraborate, it was demonstrated that fraction D did contain multiple components, all but one of which were carbohydrate-containing lipids (giving positive reactions when sprayed with orcinol-sulfuric acid reagent). Fraction D was found to contain glycerol and phosphate in equimolar ratios but did not contain nitrogen. Two sugars were detected which migrated on paper chromatograms with glucose and galactose.