Structure and Distribution of Glycosyl Diglycerides in Bacteria

Characterization of novel glycolipid antigens with an α-galactose epitope in lactobacilli detected with rabbit anti-Lactobacillus antisera and occurrence of antibodies against them in human sera

Anti-Lactobacillus johnsonii (LJ) antisera generated by immunization of rabbits with LJ reacted with glyceroglycolipids in LJ, i.e. dihexaosyl diacylglycerol (DH-DG), trihexaosyl DG (TH-DG) and tetrahexaosyl DG (TetH-DG), whose reactivities with antisera increased proportionally with longer carbohydrate chains of glycolipids. Structural analyses of glycolipids from LJ revealed that DH-DG was Galα1-2Glcα1-3'DG, and TH-DG and TetH-DG were novel derivatives of it with α-Gal at the non-reducing terminal, i.e. Galα1-6Galα1-2Glcα1-3'DG and Galα1-6Galα1-6Galα1-2Glcα1-3'DG, respectively. DH-DG was commonly present in several lactobacilli examined, but TetH-DG was restricted to LJ, L. intestinalis and L. reuteri, while the TH-DGs from L. casei were Glc1-6Galα1-2Glcα1-3'DG and an esterified derivative of it, Glc1-6Galα1-2Glc(6-fatty acid)α1-3'DG, as reported in the literature. Anti-LJ antisera reacted with TH-DG and esterified TH-DG from L. casei to lesser extents, but not at all with gentibiosyl DG from Staphylococcus epidermidis or kojibiosyl DG from Streptococcus salivalis or sphingoglycolipids containing α-Gal residues. The major molecular species of glycolipids obtained from lactobacilli were 11-octadecenoic and 11,12-methylene-octadecanoic acids-containing ones. Also, human IgM antibodies against TH-DG and TetH-DG from LJ were detected in human sera, with various antibody titres, indicating that an immune reaction to symbiotic lactobacilli occurs against their glycolipid antigens, TH-DG and TetH-DG.

Excretion into feces of asialo GM1 in the murine digestive tract and Lactobacillus johnsonii exhibiting binding ability toward asialo GM1. A possible role of epithelial glycolipids in the discharge of intestinal bacteria

In the digestive tract of mice (HR-1, 5 months old, ♀), asialo GM1 (GA1) exhibiting receptor activity toward several intestinal bacteria was preferentially expressed in the small intestine. Also, less than 10% of GA1 in the small intestine was converted into fucosylated and sulfated derivatives, but it was completely converted to fucosyl GA1 (FGA1) in the stomach, cecum and colon. Among the lipid components in these tissues, glycolipids other than Forssman antigen and cholesterol sulfate (CS) were present in the digestive tract contents. However, sulfated GA1, sulfatide and fucosyl GM1 in the gastro-intestinal contents were not present in the cecal and colonic contents, in which the major glycolipids were ceramide monohexoside (CMH), GA1 and FGA1. The total amount of GA1 in the whole contents was 20% of that in the tissues. Thus, glycolipids were stable during the process of digestion, and excreted from the body together with cholesterol and CS. On the other hand, Lactobacillus johnsonii (LJ), whose receptor is GA1, was detected in the cecal and colonic contents on sequential analysis of 16S-ribosomal RNA and TLC-immunostaining of antigenic glycolipids with anti-LJ antiserum. LJ was found to comprise 20% of the total bacteria cultured in the lactobacillus medium under aerobic conditions, and to be present in the cecal and colonic contents, 9.8 × 10(7) cells versus 37 μg GA1 and 1.4 × 10(8) cells versus 49 μg GA1, respectively. Thus, GA1 in the contents might facilitate the discharge of intestinal bacteria by becoming attached them to prevent their irregular diffusion.

Distribution of receptor glycolipids for Lactobacilli in murine digestive tract and production of antibodies cross-reactive with them by immunization of rabbits with Lactobacilli

In the digestive tract of mice (HR-1 strain), glycolipids belonging to the ganglio-series were revealed to be expressed in region-specific manners, i.e. FGA1 and FGM1 in the stomach, GA1 in the small intestine, and FGA1 and sulphatides in the cecum. The amount of GA1 as a receptor glycolipid for Lactobacilli was especially higher in the small intestine than in the other regions, it comprising 1.6-2.8 microg/mg dry weight. On immunization of rabbits with Lactobacillus johnsonii and Lactobacillus intestinalis, both of which are murine intestinal bacteria, antibodies toward bacterial glycolipids, i.e. Galalpha1-2Glcalpha1-3DG, and tri- and tetrahexaosyl DGs, were effectively generated and, in addition, they were found to cross-react with GA1 and GalCer, but not with structurally related glycolipids such as Lc(4)Cer, nLc(4)Cer and IV(3)Galalpha-nLc(4)Cer, indicating that GA1 is a preferable antigen for anti-lactobacillus antisera and suggesting the presence of epitopes common to both Lactobacilli and the host. In fact, molecules reacting with anti-GA1 antibodies were detected among bacterial proteins on Western blotting, indicating a possible occurrence of the carbohydrate structure mimicking GA1 in bacterial proteins.

Lipoteichoic acid from Bacillus licheniformis 6346 MH-1. Comparative studies on the lipid portion of the lipoteichoic acid and the membrane glycolipid

A lipoteichoic acid and a membrane glycolipid were isolated from Bacillus licheniformis 6346 MH-1. The fatty acid composition of the two preparations were similar. Most of the fatty acids were of the branched chain type. The glycolipid was shown to be a diacyl derivative of O-beta-D-glucopyranosyl-(1 leads to 6)-O-beta-D-glucopyranosyl-(1 leads to 3)-glycerol. The lipoteichoic acid contained lipid, polyglycerol phosphate, and glucosamine. The lipid was released by treatment with hydrofluoric acid and by hydrolysis in dilute acid and was shown to have a structure identical with that of the membrane glycolipid.

A genetic model for the evolution of the glycosphingolipids

The glycosphingolipids have been found in many animal tissues, but the complexity of their molecular structure varies considerably among the different phyla. Relatively simple structures have been found in invertebrate species, while the most complex have been demonstrated in brain tissue of modern fishes and amphibians. The data on the phylogenetic distribution of the glycosphingolipids has been interpreted to indicate that a significant number of gene duplications, involving many different structural genes, may have occurred during a few specific periods of vertebrate evolution. The transition from invertebrate to jawless vertebrate, the divergence of rays and skates from true sharks, the advent of modern bony fishes and the transition from aquatic to terrestrial vertebrates, each could have veen accompained by duplications of genes involved in the synthesis and degradation of glycosphingolipids. The evolutionary study of such a multi-enzyme system may be one means to detect alterations in the genome as a whole. The apparent correspondence in time of these gene duplications involved in glycosphingolipid metabolism and periods of rapid vertebrate evolution which may have been accompanied by significant increases in the amount of cellular DNA suggests that such changes may have occurred via the mechanism of tetraploidization.

Properties of a membrane-bound cardiolipin synthetase from Lactobacillus plantarum

Cardiolipin (CL) synthetase of Lactobacillus plantarum 17-5 catalyzed the stoichiometric conversion of 2 mol of phosphatidylglycerol to 1 mol of CL. The enzyme activity was linear with time for 30 min at 37 C and with protein concentration between 20 and 200 mug of protein per ml. The enzyme was membrane associated, had a pH optimum of 5.1 in phosphate buffer, and was not stimulated by Mg2+, and the activity was not affected by the addition of ethylenediaminetetraacetic acid, cytidine diphosphate diglyceride, or cytidine triphosphate. The reaction was inhibited about 95% by Triton X-100 (0.5% final concentration) and by CL, the end product of the reaction. The activity of this enzyme was studied as a function of growth. The CL synthetase specific activity was highest during the early and midexponential growth phases, as was the cellular content of CL. The results demonstrate a correlation between enzyme-specific activity and lipid content of the cells.

Effect of inhibition of protein synthesis on lipid metabolism in Lactobacillus plantarum

In Lactobacillus plantarum 17-5, lipid synthesis appears to be correlated with protein synthesis. Inhibition of protein synthesis by chloramphenicol (50 mug/ml) caused the nearly simultaneous inhibition of incorporation of radioactive oleic acid into polar lipids before the cessation of growth. In addition, de novo fatty acid synthesis, as determined by the incorporation of radioactive acetate into cellular lipids, was also inhibited. Removal of the antibiotic resulted in the resumption of growth, protein synthesis, and polar lipid synthesis. Inhibition of protein synthesis by leucine deprivation also produced a marked reduction in the incorporation of radioactive oleic acid into the total polar lipids at about the same time that growth stopped (30 to 60 min after the removal of leucine). However, the different classes of lipids behaved differently. For example, the incorporation of oleic acid into cardiolipin was inhibited immediately upon removal of leucine from the cultures, whereas incorporation into phosphatidyl-glycerol was maintained at near normal rates for 60 min after the removal of leucine and then ceased. In contrast, the accumulation of radioactive oleic acid in a neutral lipid identified as diglyceride occurred to a much greater extent in leucine-deprived cultures than in control (+ leucine) cultures. Upon addition of leucine to leucine-deprived cultures, the rates of synthesis of phosphatidyl-glycerol and cardiolipin returned to normal; the amount of radioactivity in the diglyceride fraction decreased to normal levels concomitantly with increased phospholipid synthesis.

Phosphatidylkojibiosyl Diglyceride: metabolism and function as an anchor in bacterial cell membrane

The recently discovered phosphoglycolipid, phosphatidylkojibiosyl diglyceride (PKD), was first observed as a biosynthetic by-product of glycosyl diglyceride metabolism in Streptococcus faecalis (faecium) ATCC 9790. Its structure is 1, 2-diacyl-3-O-alpha-Dglucopyranosyl-6'-O-phosphoryl- [1'', 2''-diacyl-3''-O-sn-glycerol]-alpha-D-glucopyranosyl)-sn-glycerol. The biosynthesis of phosphatidyl-kojibiosyl diglyceride occurs by a novel transphosphatidylation reaction in which a phosphatidyl glycerol to the primary alcohol function at the 6 position of the internal glucose of kojibiosyl diglyceride. The reaction is catalyzed by a membrane-derived enzyme. Phosphatidyl-kojibiosyl diglyceride is bound covalently through a phosphodiester bond to the polyglycerol phosphate moiety of membrane lipoteichoic acid from S. faecalis. Phosphatidylkojibiosyl diglyceride has four nonpolar long chain fatty acyl groups and appears to have the necessary physico-chemical properties to anchor the long hydrophilic glycerol phosphate polymer of lipoteichoic acid to the hydrophobic enviroment of the membrane of S. faecalis and probably other gram-positive bacteria as well.

Characterization of the lipids of mesosomal vesicles and plasma membranes from Staphylococcus aureus

Mesosomal vesicles and plasma membranes were isolated from Staphylococcus aureus ATCC 6538P by protoplasting and differential centrifugation. The lipids of each of the two membrane fractions were extracted with pyridine-acetic acid-N-butanol, and the nonlipid contaminants were removed by Sephadex treatment. The lipids were then separated by passage through diethylaminoethyl-cellulose columns and characterized by thin-layer chromatographic, chemical, and spectral analyses. The lipids were separated into four discrete diethylaminoethyl fractions: (i) vitamin K2, carotenoids, C55 isoprenoid alcohol, and monoglucosyl diglyceride; (ii) cardiolipin, carotenoids, phosphatidyl glycerol, diglucosyl diglyceride, and an unidentified ninhydrin-positive component; (iii) cardiolipid and phosphatidyl glyderol; (iv) cardiolipin, phosphatidyl glycerol, and phosphatidyl glucose. Qualitatively, no difference in lipid composition between mesosomal vesicles and plasma membranes was found. However, based on equal dry weights of membrane materials, a relative quantitative difference in the amount of specific lipids in mesosomal vesicles and plasma membranes was observed. There are 4 times more monoglucosyl diglyceride, 2.6 times more diglucosyl diglyceride, 3.8 times more phosphatidyl glucose, 2 times more carotenoids, and 2 times more vitamin K2 found in mesosomal vesicles than in plasma membranes. The concentration of cardiolipin and phosphatidyl glycerol is 3.6 and 6 times greater, respectively, in mesosomal vesicles.

Extractable lipids of gram-negative marine bacteria: phospholipid composition

Phospholipid compositions of 20 strains of marine and estuarine bacteria were determined. Results showed that phospholipids of marine bacteria differed very little from those of nonmarine organisms with phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol being the predominant phospholipids in all strains examined. Lyso-phosphatidylethanolamine occurred in significant quantities among a number of the marine bacteria, and two of the isolates contained significant quantities of poly-beta-hydroxybutyrate. Effects of age and growth temperature on the phospholipid composition were also investigated. It is suggested that phylogenetic relationships among bacteria may be correlated with phospholipid composition.

Lipid composition of Mycoplasma neurolyticum

The total lipid content of Mycoplasma neurolyticum comprises about 14% of the dry weight of the organisms and is about equally distributed between the phospholipid and the neutral-glycolipid fractions. The neutral lipids were identified as triglycerides, diglycerides, and cholesterol. The glycolipid fraction contained 1-O-beta-glucopyranosyl-d-2,3-diglyceride and 1-[O-beta-d-glycopyranosyl-(1-->6)-O-beta-d-glucopyranosyl]-d-2,3-diglyceride. The latter lipid is structurally identical to the diglucosyl diglyceride which occurs in Staphylococcus aureus. The phospholipids of the organism consist of a fully acylated glycerophosphoryl-glycerophosphoryl glycerol, phosphatidic acid, diphosphatidyl glycerol, phosphatidyl glycerol, and amino acyl esters of phosphatidyl glycerol. Phosphatidic acid and phosphatidyl glycerol account for greater than 90% of the phospholipids of organisms in the exponential phase of growth. The predominant fatty acids found in all of the acyl lipids were palmitic, stearic, and oleic acids.

The effect of the polar moiety of lipids on the ion permeability of bilayer membranes

Bilayer membranes were prepared with the negatively charged lipids phosphatidylglycerol and diphosphatidylglycerol, the positively charged lipid lysyl phosphatidylglycerol, the zwitterionic lipid phosphatidylethanolamine, and an uncharged glycolipid, diglucosyldiglyceride, all isolated from gram-positive bacteria. Bilayer membranes of all these lipids manifested specific resistances of 10(7) to 10(9) Ω cm(2) and capacitances of 0.3 to 0.4 μF cm(-2). The membrane potentials of these bilayers were measured as a function of the sodium chloride, potassium chloride, and hydrogen chloride transmembrane concentration gradients (0.01 to 0.10M) and were found to be linear with the logarithm of the salt activity gradients. Membranes made from lysyl phosphatidylglycerol (one net positive charge) were almost completely chloride selective, whereas membranes from phosphatidylglycerol and diphosphatidylglycerol (one and two net negative charges, respectively) were highly cation selective. Membranes prepared with either diglucosyldiglyceride or phosphatidylethanolamine showed only slight cation selectivity. These findings indicate that the charge on the polar head group of membrane lipids plays an important role in controlling the ion-selective permeability of the bilayer.

Metabolism of the glycosyl diglycerides and phosphatidylglucose of Staphylococcus aureus

A glucose containing lipid, phosphatidylglucose (probably 3-sn-phosphatidyl-1'-glucose) and a lipid tentatively identified as phosphatidylethanolamine have been characterized in the lipids of Staphylococcus aureus. These lipids together comprise less than 2% of the total phospholipids of exponentially growing S. aureus and accumulate to 14% of the total phospholipid in stationary-phase cells. These lipids lost no (32)P when cells grown with H(3) (32)PO(4) were transferred to nonradioactive medium during the exponential growth phase. This was in marked contrast to the other phospholipids which lost (32)P rapidly. The loss of (32)P from phosphatidic acid and cardiolipin in exponentially growing cells was biphasic, suggesting heterogeneity of phospholipid phosphate metabolism. The mono- and diglucosyl diglycerides showed a rapid loss of (14)C-glucose during growth in nonradioactive medium but no loss of (14)C from the fatty acids of these lipids. The (14)C in the glucose and fatty acids of the glucosyl diglycerides was derived from glucose.

Characterization of the lipids of Butyrivibrio fibrisolvens

Butyrivibrio fibrisolvens strain D-1 was grown on a lipid-free chemically defined medium. The lipids were extracted with chloroform-methanol and separated into nonpolar and polar fractions by silicic acid column chromatography. Further separations were made by preparative thin-layer chromatography. The lipid fractions were identified by specific staining reactions and R(F) values, by phosphorus and nitrogen determinations, by chromatography of hydrolysis products, and by the use of infrared spectroscopy. The major nonpolar lipid was free fatty acid. Four major polar lipids were identified: phosphatidylethanolamine, phosphatidyl glycerol, lipoaminoacid, and glycolipid. The lipoaminoacid contained alanine, leucine, and isoleucine. The glycolipid contained galactose. The major fatty acids identified were C16:0 and C18:1. The significance of the presence of lipoaminoacid is discussed.

Lipid composition of Bacillus cereus during growth and sporulation

The lipid composition of Bacillus cereus during growth and sporulation was examined. The total lipid extract accounted for 2 to 3% of the dry weight of the cells and consisted of neutral lipids (30 to 40%) and phospholipids (60 to 70%). Phospholipids were separated by thin-layer chromatography into eight components; phosphatidyl ethanolamine, phosphatidyl glycerol, and diphosphatidyl glycerol were the major phospholipids and accounted for over 90% of the total. Also identified was a diglycosyl diglyceride and an alanine ester of phosphatidyl glycerol. Diphosphatidyl glycerol was more difficult to extract than the other components in vegetative and stationary-phase cells, but became increasingly easy to extract during spore maturation, and during sporulation cellular levels increased. Phosphatidyl glycerol had a high turnover rate; it accounted for about 70% of the phospholipid synthesis throughout sporulation but only represented between 30 and 40% of the total phospholipid at any time. Phosphatidyl ethanolamine, on the other hand, accounted for about 20% of the synthesis but was the major phospholipid (50 to 60% of the total).

Biosynthesis of glucosyl diglycerides by Mycoplasma laidlawii strain B

Monoglucosyl diglyceride is synthesized from 1,2-diglyceride and uridine-5'-diphosphoglucose (UDP); diglucosyl diglyceride from monoglucosyl diglyceride, and uridine-5'-diphosphoglucose by membranes of Mycoplasma laidlawii strain B. All of these enzymatic activities reside in the membrane. Membranes solubilized by detergent action or succinylation and acetone powders of membranes were inactive. Requirements for Mg(2+), UDP, and appropriate lipid acceptor were demonstrated for biosynthesis of both glycolipids. Glucose-1-phosphate plus uridine triphosphate could replace the UDP requirement. A medium of relatively high ionic strength and a critical concentration of sodium lauryl sulfate stimulated biosynthesis of the monoglucosyl diglyceride. The optimal pH for both reactions was 8.0. A specificity for 1,2-diglyceride from the homologous organism was found for optimal synthesis of the monoglucosyl diglyceride, and a specificity for monoglucosyl diglyceride was found in the case of diglucosyl diglyceride synthesis. Both reactions were specific for UDP.

Separation and identification of the polar lipids of Chromatium strain D

The polar lipids of the autotrophically grown, obligately anaerobic, photosynthetic bacterium Chromatium strain D were separated by paper chromatography. Four major phospholipids were identified: lysophosphatidylethanolamine, phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin. In addition, three glycolipids were observed and characterized, namely, monoglucosyldiglyceride, which is found in other biological systems, and (mannosyl, glucosyl)-diglyceride and (dimannosyl, glucosyl)-diglyceride, which heretofore have not been observed in nature.