Homeoviscous theory under pressure. I. The fatty acid composition of Tetrahymena pyriformis NT-1 grown at high pressure

Tetrahymena was grown at up to 260 atm to see if the bilayer-ordering effect of pressure increased the proportion of unsaturated fatty acids in the membrane lipids. Both whole cells and microsomes showed no such change in their fatty acid composition. The most striking effect was seen in the former which showed a pressure-dependent increase in the proportion of C16:0 in relation to C16:Δ9. Homeoviscous adaptation to pressure does not appear to occur in this cell.     

Proteomic profile changes in membranes of ethanol-tolerant <Emphasis Type="Italic">Clostridium thermocellum</Emphasis>

Clostridium thermocellum, a cellulolytic, thermophilic anaerobe, has potential for commercial exploitation in converting fibrous biomass to ethanol. However, ethanol concentrations above 1% (w/v) are inhibitory to growth and fermentation, and this limits industrial application of the organism. Recent work with ethanol-adapted strains suggested that protein changes occurred during ethanol adaptation, particularly in the membrane proteome. A two-stage Bicine-doubled sodium dodecyl sulfate-polyacrylamide gel electrophoresis protocol was designed to separate membrane proteins and circumvent problems associated with membrane protein analysis using traditional gel-based proteomics approaches. Wild-type and ethanol-adapted C. thermocellum membranes displayed similar spot diversity and approximately 60% of proteins identified from purified membrane fractions were observed to be differentially expressed in the two strains. A majority (73%) of differentially expressed proteins were down-regulated in the ethanol-adapted strain. Based on putative identifications, a significant proportion of these down-regulated proteins were involved with carbohydrate transport and metabolism. Approximately one-third of the up-regulated proteins in the ethanol-adapted species were associated with chemotaxis and signal transduction. Overall, the results suggested that membrane-associated proteins in the ethanol-adapted strain are either being synthesized in lower quantities or not properly incorporated into the cell membrane.     

脂肪酸对盐胁迫大麦幼苗液泡膜微囊膜脂组分及功能的影响

用１００ｍｍｏｌ／ＬＮａＣｌ处理大麦（ＨｏｒｄｅｕｍｖｕｌｇａｒｅＬ．）幼苗２ｄ,根系液泡膜微囊膜脂不饱和度上升,并不随外源脂肪酸的饱和度而改变。外源硬脂酸和亚油酸降低大麦幼苗对Ｎａ＋的吸收及其向地上部的运输,增加Ｋ＋的吸收和向地上部的运输,降低根系的电解质渗漏率。增加液泡膜磷脂、糖脂结合半乳糖含量及Ｈ＋ＡＴＰａｓｅ和Ｈ＋ＰＰａｓｅ（焦磷酸酶）活性,与它们调节大麦对离子的吸收、分配的结果相一致,硬脂酸和亚油酸均有一定程度的缓解盐害的效应,亚油酸的效应大于硬脂酸     

The influence of the fatty acid composition of Acholeplasma laidlawii membranes on the growth inhibitory activity of narasin,a polyether ionophorous antibiotic

Narasin, a polyether ionophorous antibiotic capable of acting as a transmembrane carrier of cations, has a growth inhibitory effect on Acholeplasma laidlawii, permitting only 20% survival when present at 0.1 μg/ml in an undefined growth nutrient or fatty acid-deficient nutrient supplemented only with palmitic acid. When A. laidlawii is propagated in fatty acid-deficient nutrient supplemented with linoleic acid, however, the organisms become 40 times more sensitive to the growth inhibitory effect of this antibiotic. The actual fatty acid compositions of the membranes would indicate that a higher degree of unsaturation enhances ionophore activity.     

14种微藻总脂含量和脂肪酸组成研究

比较分析了14种微藻的总脂含量和脂肪酸组成,结果表明：除小球藻、亚心形扁藻、极微小环藻、微绿球藻外,其他微藻的总脂含量均超过其干重的10％。每一纲的微藻脂肪酸组成都有各自特点,绿藻纲中16：0、16：1(n-7)、18：1(n-9)含量较高,但微绿球藻中16：1(n-7)、20：5(n-3)(EPA)含量远高于其他绿藻;金藻纲中含大量14：0、16：0、18：3(n-3)、22：6(n-3)(DHA);硅藻纲中14：0、16：0、16：1(n-7)、EPA含量较高;黄藻纲的异胶藻富含16：0、16：1(n-7)和EPA。     

Specificity of fatty acid composition of highly migratory fish. A comparison of docosahexaenoic acid content in total lipids extracted in various organs of bonito (Euthynnus pelamis)

Fatty acid composition of lipids in various organs of the bonito (Euthynnus pelamis), a typical species within the tuna species, caught in the sea off the Pacific coast of Japan, was determined by gas-liquid chromatography. The major fatty acids of all organs examined were palmitic acid (16:0), palmitoleic acid (16:1), oleic acid (18:1), icosapentaenoic acid (20:5), and docosahexaenoic acid (22:6). 22:6 (DHA) was the dominant fatty acid accounting for 25% or more of the total fatty acids in all organs of the bonito, caught in the sea off the Japanese coast.     

Fatty acid effects on calcium influx and efflux in sarcoplasmic reticulum vesicles from rabbit skeletal muscle

Low concentrations of fatty acids inhibited initial Ca uptake by sarcoplasmic reticulum vesicles, the extent of inhibition varying with chain length and unsaturation in a series of C₁₄–C₂₀ fatty acids. Oleic acid was a more potent inhibitor of initial Ca uptake than stearic acid at 25°C, whereas at 5°C there was less difference between the inhibitory effects of low concentrations of these fatty acids. When the fatty acids were added later, during the phase of spontaneous Ca release that follows Ca uptake in reactions carried out at 25°C, 1–4 μM oleic and stearic acids caused Ca content to increase. This effect was due to marked inhibition of Ca efflux and slight stimulation of Ca influx. At concentrations of >4 μM, both fatty acids inhibited the Ca influx that occurs during spontaneous Ca release; in the case of oleic acid, this inhibition resembled that of initial Ca uptake at 5°C. The different effects of fatty acids at various times during Ca uptake reactions may be explained in part if alterations in the physical state of the membranes occur during the transition from the phase of initial Ca uptake to that of spontaneous Ca release.     

The sphingomyelin pools in the outer and inner layer of the human erythrocyte membrane are composed of different molecular species

Analyses of the fatty acid composition of the outer and inner pools of sphingomyelin in the human erythrocyte membrane revealed significant differences in molecular species composition of these two pools. The sphingomyelin in the inner monolayer, representing 15–20% of the total sphingomyelin content of this membrane, is characterized by a relatively high content (73%) of fatty acids, which have less than 20 carbon atoms, whereas these account for only 31% of the total fatty acids in the sphingomyelin in the outer leaflet. On the other hand, the ratio saturated/unsaturated fatty acids in the two pools is similar. Significant differences are also observed for the fatty acid composition of the sphingomyelin in human serum when compared to that in the outer monolayer of the corresponding red cell. These results are interpreted to indicate an (almost) complete absence of transbilayer movements of sphingomyelin molecules in the human erythrocyte membrane, whereas an exchange of this phospholipid between the red cell membrane and serum is either virtually absent, or affects only a minor fraction of the sphingomyelin in the outer membrane layer.     

高寒山区牧草根质膜和脂肪酸组分对冷冻低温的适应反应

在秋末冬初测定了高寒山区自然生境中生长的垂穗披碱草(Elymus nutans)、早熟禾(Poa sphyondylodes) 和花雀麦(Bromus sinensis)3种牧草根膜脂脂肪酸组分和质膜流动性及ATPase活力。结果表明：随着秋末冬初气温下降到0℃以下,3种牧草根中膜脂肪酸配比发生较大变化,棕榈酸相对百分含量下降40.29％,亚油酸增加3倍多,亚麻酸增加112.39％,脂肪酸不饱和指数(IUFA)增大;同时根质膜流动性在低温期间较大,在融冻阶段有下降,冰冻阶段增大;质膜Mn2+ATPase、Ca2+ ATPase活力增大,Mg2+ ATPase活力下降。在冷冻适应中牧草根膜脂脂肪酸不饱和度的增加直接影响着膜的流动性,影响膜功能和植物抗冻性,并在维持根细胞膜完整性和抵抗组织结冰伤害方面起重要作用。     

Localization and immunological characterization of the cellulolytic enzyme system in Clostridium thermocellum

Abstract The cellulolytic enzyme complex from Clostridium thermocellum JW 20 was purified from the cellulose to which the enzyme was bound during growth. After centrifugation and gel filtration the enzyme complex was analyzed by SDS-PAGE. Three subunits with apparent molecular weights of 195 000 Da, 97 000 Da and 72 000 Da were purified by preparative SDS-PAGE and electroelution. Polyclonal antibodies directed against these three subunits were raised in rabbits. The specificity of the antisera was tested with immunochemical methods. Cross reactions with other subunits of the cellulase complex were observed. Immunoelectron microscopy of protein-A gold labeled, resin embedded cells indicated that the three types of subunits were located in the outer region of the cytoplasm and on structures at the outside of the cell wall.     

梭热杆菌纤维小体研究进展

梭热杆菌(Clostridium thermocellum)是一种嗜热厌氧细菌,通过分泌大量纤维素酶高效降解纤维素.根据作用纤维素的不同部位,梭热杆菌分泌的纤维素酶分为内切纤维素酶和外切纤维素酶.纤维小体是由支架蛋白、锚定元件、黏合蛋白、纤维素结合域和催化单位组成的复合体,其独特的结构,使得它可以比真菌纤维素酶更紧密地结合到纤维素表面,这个复合结构结合着多种催化单位,而此特殊的结构是梭热杆菌高效降解纤维素的必要条件.近年来,为更深入透彻地了解纤维小体的结构与功能进行了大量的研究工作,现对相关研究进展进行综述,并给出了未来可能的发展方向.     

The effect of low oxygen concentration on the acyl-lipid and fatty-acid composition of the C4 plant Amaranthus paniculatus L.

Acyl lipids and their constituent fatty acids were studied in leaves, chloroplasts and bundle-sheath strands of the C₄ plant Amaranthus paniculatus L. grown under normal and 4%-oxygen-containing atmospheres. In all fractions the major lipids were found to be monogalactosyldiacylglycerol, digalactosyldiacylglycerol, sulphoquinovo-syldiacylglycerol and phosphatidylglycerol. Significant quantities of phosphatidylcholine and phosphatidylethanolamine were restricted to leaves and bundle-sheath strands. All lipids, except phosphatidylglycerol where 3-trans-hexadecenoic acid was also present, contained palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid. On a chlorophyll basis and compared with whole leaves, the amounts of phosphatidylcholine and phosphatidylethanolamine in bundle-sheath strands were considerably reduced. Three weeks after the change from a normal to a 4% atmospheric O₂ level, the galactolipid content, particularly in the bundlesheath strands, was enhanced. There were no significant differences in the degrees of saturationunsaturation of total acyl lipid for the plants grown in the low oxygen and normal atmospheres, although under 4% O₂ the phosphatidylglycerol contained an increased proportion of 3-trans-hexadecenoic acid at the expense of palmitic acid.Abbreviations DGDG digalactosyldiacylglycerol - MGDG monogalactosyldiacylglycerol - PC phosphatidylcholine - PE phosphatidylethanolamine - PG phosphatidylglycerol - SQDG sulphquinovosyldiacylglycerol     

外源胆固醇对水稻幼苗膜脂组成及抗冷力的影响

分析了水稻幼苗低温胁迫前后膜脂和膜脂脂肪酸含量变化。结果表明,经胆固醇处理的幼苗叶和根细胞膜脂中LPC、PS和PG含量比对照下降少,PA含量增加也较少。胆固醇处理的幼苗叶和根棕榈酸(16:0)增加量和亚麻酸(18:3)与IUFA减少量均明显比对照少。试验结果证明,水稻幼苗叶片和根系的抗冷力与PA含量和脂肪酸不饱和程度变化有密切关系。外源胆固醇处理水稻幼苗能阻止低温对膜脂的破坏作用,提高幼苗抗低温胁迫能力。     

Breakdown of crystalline cellulose by synergistic action between cellulase components from Clostridium thermocellum and Trichoderma koningii

Abstract Certain isolated components of fungal cellulases, which cannot effect the breakdown of highly ordered cellulose individually, interact together synergistically to do so when recombined. Suprisingly, not all fungal cellulase components exhibit this property, and no such synergism has been observed so far between fungal and bacterial cellulases.
The cellulase complex of Clostridium thermocellum cannot effect the extensive breakdown of highly ordered cellulose unless Ca²⁺ and dithiothreitol (DTT) are present. However, we now report that isolated cellobiohydrolase from Trichoderma koningii can combine with C. thermocellum cellulase to effect the breakdown of cellulose in the absence of Ca²⁺ and DTT. enhanced activity is observed if Ca²⁺ and DTT are present.
This finding may have important applications in industry: it certainly has important implications for those interested in the basic mechanism of cellulase action in C. thermocellum .     

The effect of ethanol on the phase behavior of membrane lipids extracted from Clostridium thermocellum strains

The phase behavior of aqueous dispersions of extracted lipids from Clostridium thermocellum wild-type and ethanol-tolerant C919 cells has been examined by DSC. The optimum growth temperature of this anaerobe is 60°C. The wild-type lipids exhibit a broad phase transition centered at 30°C; the C919 mutant lipids show a 10°C lower T_m. The direct addition of growth inhibiting concentrations of ethanol has no significant effect on T_m or headgroup mobility (monitored by ²H-NMR) of either set of lipids. In contrast, wild-type cells adapted to growth in ethanol exhibit a broadened and lower T_m (15–25°C plateau); C919 membrane lipids do not exhibit significantly altered phase behavior when adapted to growth in ethanol. Both wild-type and mutant membranes have fatty acid composition changes upon growth in ethanol, which increases lower-melting components. It is concluded that fatty acid changes which occur upon adaptation of the organism to growth in ethanol are secondary responses and not necessarily direct responses to alter membrane fluidity.     

Fatty acid alterations in Saccharomyces cerevisiae exposed to ethanol stress

The influence of ethanol concentration on fatty acid alterations in total phospholipids (PL), phosphatidylcholine (PCH), phosphatidylethanolamine (PE), phosphatidylinositol (PI), sterol esters (ES) and triacylglycerols (TAG) of Saccharomyces cerevisiae was studied. Ethanol induced the elevation of palmitic and oleic acid level in major membrane phospholipids (PCH and PE) and also the palmitoleic acid content in ES and TAG.