Chemical structure of the ether lipids of thermophilic acidophilic bacteria of the Caldariella group

The lipids of the Caldariella group of extremely thermophilic acidophilic bacteria are based on a 72-membered macrocyclic tetraether made up from two C₄₀ diol units and either two glycerol units or one glycerol and one nonitol. The C₄₀ components have the 16,16′-biphytanyl skeleton and the detailed structure of three of them is established.     

Structure of calditol,a new branched-chain nonitol,and of the derived tetraether lipids in thermoacidophile archaebacteria of the Caldariella group

A second category of membrane lipids in extreme thermoacidophile archaebacteria of the Caldariella group is based on the same type of macrocyclic tetraether, incorporating two 16,16′-biphytanyl chains, as those described earlier, but only one of the hydrophilic components is glycerol; the second hydrophilic component is calditol, a unique branched-chain nonitol. It is also shown that in the biphytanyl chains there can be up to 4 cyclopentane rings whose location is demonstrated.     

Incorporation of labelled glycerols into ether lipids in Caldariella acidophila

The lipids of Caldariella acidophila, an extreme thermophile member of the new archaebacteria group, are macrocyclic tetraethers. They are made up of two glycerol molecules (or one glycerol and one nonitol) bridged through ether linkages by two C₄₀16,16′-biphytanyl chains. To elucidate the biosynthesis of the glycerol moiety of these tetraethers and the mechanism of glycerol ether assembly, labelled [U-¹⁴C, 1(3)-³H]glycerol and [U-¹⁴C, 2-³H]glycerol, were fed to C. acidophila. Both precursors were selectively incorporated with high efficiency, and without any change in the ³H/¹⁴C ratio, in the glycerol moiety of tetraethers. These results suggest that the ether forming step in the biosynthesis of tetraether lipids of C. acidophila, occurs without any loss of hydrogen from any of the glycerol carbons which in turn could be directly alkylated by geranylgeranyl pyrophosphate. The incorporation of radioactivity in the isoprenoid chains and into nonitol is also analysed.     

Complex lipids of Caldariella acidophila,a thermoacidophile archaebacterium

Isoprenoid ether lipids are common to the ‘urkingdom’ archaebacteria, within which members of the Caldariella group of extreme thermoacidophiles and some methanogenic species have lipids based on macrocyclic tetraethers containing two 16,16′-biphytanyl chains. As a step towards closer classification, the complex lipids of Caldariella acidophila have been more fully characterized.     

A new respiratory quinone, 2-methyl-3-VI,VII-tetrahydroheptaprenyl-1,4-naphthoquinone isolated from Thermoleophilum album

Abstract A new menaquinone has been isolated from the Gram-negative bacterium, Thermoleophilum album , an organism obligate for thermophily and n -alkane substrates. On the basis of mass spectrometry and proton nuclear magnetic resonance (¹H-NMR) spectrometry the novel quinone is shown to correspond to 2-methyl-3-VI,VII-tetrahydroheptaprenyl-1,4-naphthoquinone.     

Carbon isotope-labelling experiments indicate that ladderane lipids of anammox bacteria are synthesized by a previously undescribed, novel pathway

Ladderane lipids are unusual membrane lipids of bacteria that anaerobically oxidize ammonium to dinitrogen gas (anammox). Ladderane lipids contain linearly concatenated cyclobutane rings for which the pathway of biosynthesis is currently unknown. To investigate the possible biosynthetic routes of these lipids, 2-¹³C-labelled acetate was added to a culture of the anammox bacterium Candidatus Brocadia fulgida. Labelling patterns obtained by high-field ¹³C nuclear magnetic resonance spectroscopy of isolated lipids indicated that C . Brocadia fulgida synthesizes C_16:0 and iso C_16:0 fatty acids according to the known pathway of type II fatty acid biosynthesis. The ¹³C-labelling pattern of the C₈ alkyl chain of the C₂₀ [3] ladderane monoether also indicated the use of this route. However, carbon atoms in the cyclobutane rings and the cyclohexane ring were nonspecifically labelled and did not correspond to known patterns of fatty acid synthesis. Taken together, our results indicate that it is unlikely that ladderane lipids are formed from the cyclization of polyunsaturated fatty acids as hypothesized previously and suggest an alternative, although as yet unknown, pathway of biosynthesis.     

Monolayers of ether lipids from archaebacteria

The surface behavior of six different ether lipids from archaebacteria, based on condensation of glycerol or more complex polyols with two isoprenoid alcohols at 20 or 40 carbon atoms, was investigated in monolayers at the air-water interface.The compounds with no complex polar group (GD, GDGT, GDNT) form monolayers showing a reversible collapse at surface pressure as low as 22 dynes/cm. This collapse pressure decrease with temperature in such a way that the film tension remains constant. In condensed films, these molecules do not assume a completely upright position.Lipids with complex polar ends (HL, GLB, PLII) form films more stable to compression. Forcearea characteristics and surface moment values of HL monolayers are similar to those of analogous ester lipids with fatty acid chains. Monolayers of the two bipolar lipids, GLB and PLII, at room temperature present a more condensed state, probably due to the lateral cohesion between long alkyl chains, but a lower collapse pressure.For all bipolar lipids, the area expansion induced by temperature increase is larger than that of monopolar ones.Abbreviations GD Glycerol diether (2,3-di-O-phytanyl-sn-glycerol - GDGT Glycerol-dialkyl-glycerol tetraether - GDNT Glycerol-dialkyl-nonitol tetraether - GLB Glycolipid B - PLII Phospholipid II - HL Total lipid extract from Halobacterium halobium     

Effects of temperature on ether lipid composition of Caldariella acidophila

The composition of the ether lipids of a strain of Caldariella acidophila, with respect to the different numbers of cyclizations of the biphytanyl components, is shown to differ between the various complex lipid classes, but the degree of cyclization increases systematically with the growth temperature in the range 75–89°. The problem of distinguishing adaptive from phyletic features in archaebacterial lipids is considered.     

Synthesis and chiroptical properties of neutral ether lipids

A variety of neutral ether lipids was synthesized. A method for the synthesis of 1,3-O-dialkyl-sn-glycerols was developed which involves selective alkylation of 3-O-alkyl-sn-glycerols. The ORD and CD curves of the various glyceryl ethers and their esters were analyzed. The correlation between the CD sign of the acyl residue and its position in the glycerol derivative was clarified.     

Temperature range variants of Bacillus megaterium

Facultatively and obligately thermophilic variants were isolated from 3 out of 12 tested mesophilic Bacillus megaterium strains. The variants occurred at a frequency of 10^-8–10^-9. The ability to grow at elevated temperatures was cured by means of treatment with acridine orange. Stable revertants were isolated from facultatively and obligately thermophilic variants. An unknown type of megacin was produced by the facultative thermophiles. This megacin attacked mesophilic and obligately thermophilic strains. The thermophiles displayed a few divergent taxonomic characteristics but a close relationship between the strains was indicated by the megacin spectrum and sensitivity to phage. Arrhenius plots revealed that the strains could be considered as temperature range variants and that the temperature characteristic increased with growth at a higher temperature range. The case for a plasmid involvement in the phenomenon is discussed.Abbreviations M Mesophilic - Fp facultatively psychrophilic - Ft facultatively thermophilic - Ot obligately thermophilic     

TOTAL LIPID PRODUCTION OF THE GREEN ALGA NANNOCHLOROPSIS SP. QII UNDER DIFFERENT NITROGEN REGIMES1

The green alga Nannochloropsis sp. QII was cultivated in media with sufficient and growth-limiting levels of nitrogen (nitrate). Nitrogen deficiency promoted lipid synthesis yielding cells with lipids comprising 55% of the biomass. The major lipids were triacylglycerols (79%), polar lipids (9%) and hydrocarbons (2.5%). The polar lipids consisted of a broad range of phospholipids, glycolipids and sulfolipids. Other lipids identified were pigments, free fatty acids, saponifiable and unsaponifiable sterol derivatives, various glycerides, a family of alkyl-1, 4-dioxane derivatives and a series of alkyl- and hydroxyalkyl-dimethyl-acetals. Experiments in which ¹⁴CO₂ was provided at different times in the growth cycle demonstrated that enhanced lipid biosynthesis at low nitrogen levels resulted principally from de novo CO₂ fixation.     

Saturated and unsaturated 1-O-alkyl-2-O-acetoyl-sn-glycero-3-phosphocholines derived from ratfish liver oil: effect on human leukocyte migration

A mixture of 1-O-alkyl-2-O-acetoyl-sn-glycero-3-phosphocholines containing saturated alkyl moieties and a mixture of such compounds with saturated and unsaturated alkyl moieties, prepared from ratfish (Hydrolagus colliei) liver oil, were studied for their in vitro effect on human neutrophil migration. The mixture containing unsaturated compounds (II) was more active compared to the saturated (I) ones at a range from 10^-6 M to 10^-10 M concentrations. At 10^-4 M, II was cytotoxic. Both I and II were more potent than synthetic ‘PAF-acether’ (III) and the material prepared from beef heart plasmalogens (IV). Preincubation and checker-board titration experiments showed that the ether phospholipids derived from ratfish liver oil have primarily chemokinetic, but also chemotactic effects on neutrophils, as has been reported for compound III. These compounds are therefore highly potent stimulants of human neutrophils with potentially unique membrane-activating properties.     

Diacyl,Alkylacyl, and Alkenylacyl Phospholipids of Meloidogyne javanica Females

The phospholipid composition and acyl, alkyl, and alkenyl group compositions of diacyl, alkylacyl, and alkenylacyl phosphoglycerides of M. javanica were investigated. Phospholipid was comprised of 61.7% choline phosphoglyceride, 22.0% ethanolamine phosphoglyceride, and smaller quantities of six other lipids. Phospholipid fatty acid was more unsaturated than neutral lipid fatty acid and contained 61.3% octadecenoic (18:1) acid. Fatty acid at the 1-position of diacyl phospholipids was shorter and more saturated than that at the 2-position. Compared to choline phosphoglyceride, ethanolantine phosphoglyceride contained less 18:1 and 20:5 and more 18:0 and 20:0 acid. Alkenylacyl and alkylacyl compounds comprised 34.6% and 9.3%, respectively, of the ethanolamine phosphoglyceride but only 0.5% and 0.6% of the choline phosphoglyceride. Alkenylacyl and alkylacyl ethanolamine phosphoglycerides contained a smaller percentage of 20-carbon polyunsaturated acid at their 2-positions than did their diacyl analogue. At least 95% of the alkenyl and alkyl groups were 18:0 compounds. Tomato roots did not contain alkenylacyl or alkylacyl phosphoglycerides; their occurrence in M. javanica is a significant biochemical difference between the nematode and its host.     

Synthesis of 2,3-di-O-phytanyl-1-O-(α-D-glucopyranosyl)-sn-glycerol derivatives,analogues of polar lipids isolated from a halophilic bacterial strain

2,3-Di-O-phytanyl-1-O-glucopyranosylglycerol and polar derivatives of its 6-glucose moiety have been synthesized. The target molecule contains the diphytanyl-sn-glycerol moiety which is -linked to glucose. The key step in its synthesis involves the coupling of phytanyl bromide and isopropylidene threitol. We also demonstrated that the 6-hydroxyl group of glycolipids can be functionalized without protection of the sugar moiety.     

Semisynthetic preparation of choline and ethanolamine plasmalogens

Choline and ethanolamine plasmalogens containing defined acyl chains are prepared by deacylation and reacylation of beef heart plasmalogens. During the reactions, the amino group of ethanolamine plasmalogens is protected by the trityl group. Deacylation is achieved by mild alkaline hydrolysis, and the lysoplasmalogens are reacylated with oleoylimidazolide in the presence of the methylsulfinylmethide anion. The protective group is removed from N-trityl ethanolamine plasmalogen by treatment with silicic acid in hexane. The choline and ethanolamine plasmalogens prepared by the procedures described are free of geometric, positional and steric isomers.     

细菌纤维素的研究进展

细菌纤维素是由醋酸杆菌属、根瘤菌属、土壤杆菌属、八叠球菌属等的某些细菌在一定条件下产生的,其中最有代表性的细菌是木醋杆菌。与传统植物纤维素相比,细菌纤维素具有很高的化学纯度。主要介绍细菌纤维素性质、生物合成的方法及其在食品工业、造纸工业和作为一种生物材料在医学工程等方面的应用。