发菜膜脂及其脂肪酸组成

对野生发菜(Nostocflagelliforme Bom.et Flab)的膜脂(主要成分为类囊体膜脂)及其脂肪酸组成进行了测定分析.发菜的膜脂由单半乳糖甘油二酯(MGDG)、双半乳糖甘油二酯(DGDG)、磷酯酰甘油(PG)和硫代异鼠李糖甘油二酯(SQDG)组成,其酯酰基连接有棕榈酸(16:0)、十六碳烯酸(16:1)、硬脂酸(18:0)、油酸(18:1)、亚油酸(18:2)和亚麻酸(18:3)6种脂肪酸.发菜的不饱和脂肪酸含量可达总脂的73%,特别是16:1和18:3分别高达29%和34%,远远高于已报道的其他蓝藻,说明了发菜类囊体膜具有较强的抗逆性特点.同时还对复水30 min和复水后生长24 h的发菜膜脂及其脂肪酸组成进行了分析.结果表明,复水对野生发菜的膜脂及其脂肪酸组成没有显著影响,说明发菜的膜脂和脂肪酸组成在干燥-吸水过程中能保持很高的稳定性.     

Membrane lipid composition of the unusual cyanobacterium Gloeobacter violaceus sp. PCC 7421, which lacks sulfoquinovosyl diacylglycerol

Gloeobacter violaceus sp. PCC 7421 is an unusual cyanobacterium with only one cellular membrane, which lacks the thylakoid membranes found in other oxygenic photosynthetic organisms. The cell membrane lipids in G. violaceus sp. PCC 7421 are monogalactosyl diacylglycerol, digalactosyl diacylglycerol, phosphatidyl glycerol and phosphatidic acid in the molar proportion of 51, 24, 18 and 4% respectively. This lipid composition resembles that of the cell membrane from other cyanobacteria, but completely lacks sulfoquinovosyl diacylglycerol. This lack of sulfoquinovosyl diacylglycerol is exceptional for a photosynthetic membrane. The membrane lipids are esterified to 14:0, 16:0, 16:1, 18:0, 18:1, 18:2 and α18:3 fatty acids. Received: 28 December 1995 / Accepted: 26 April 1996     

Adaptation of Synechococcus sp. PCC 7942 to phosphate starvation by glycolipid accumulation and membrane lipid remodeling

Organisms use various adaptive strategies against phosphate stress, including lipid remodeling. Here, the response of major membrane lipids to phosphate stress was analyzed in Synechococcus sp. PCC 7942. Unlike plants and eukaryotic microalgae, no significant increases in neutral lipids were found, whereas glycolipids content increased to as high as 6.13% (of dry cell weight, DCW) and phospholipids decreased to 0.34% (of DCW) after 16 days of cultivation without phosphate. Glycolipids accumulation were mainly attributed to the significant increase of digalactosyldiacylglycerol (DGDG) by 50% and sulfoquinovosyldiaclglycerol (SQDG) by 90%, both of which acted as complementary lipids for phosphatidylglycerol (PG) in the cyanobacterial membrane. Also, a notable increase in content (by 48%) of C18 fatty acids (especially C18:1) was observed in all glycolipids at the expense of C12 and C14 (72%). These changes may contribute to membrane fluidity and photosynthetic activity for basic cell metabolism and phosphate stress adaptation. Lipidomic analyses showed the reduction of PG 18:1/16: 0 (by 52%) with the increase of DGDG 18:1/16:0 (133%) and SQDG 18:1/16:0 (245%), strongly suggesting a direct conversion of PG to DGDG and SQDG. Moreover, the decreasing amount of monogalactosyldiacylglycerol (MGDG) 16:1/16:0 (22%) was consistent with the increase of free fatty acids (125%) on day 2 of phosphate absence, which suggested that MGDG is more likely to provide a pool of fatty acids for de novo synthesis of glycolipids. This study provides valuable insight into cyanobacteria adaptation strategies to phosphate stress by membrane lipid remodeling and unveils the underlying acyl chain fluxes into glycolipids.     

Temperature-induced specific lipid desaturation in the thermophilic cyanobacterium Synechococcus vulcanus

Cyanobacteria desaturate fatty acids in the membrane lipids in response to decrease in temperature. We examined the changes in lipid and fatty acid composition in the thermophilic cyanobacterium Synechococcus vulcanus, which is characterized by an optimum growth temperature of 55°C. During temperature acclimation to 45°C or 35°C, the cells synthesized oleic acid at the expense of stearic acid in the membrane lipids. Unlike mesophilic cyanobacteria, S. vulcanus did not show any significant adaptive desaturation in the galactolipids monogalactosyl diacylglycerol and digalactosyl diacylglycerol, that comprise 50% and 30% of total membrane lipids, respectively. The major changes in fatty acid unsaturation were observed in the sulfolipid sulfoquinovosyl diacylglycerol.     

Changes in Membrane Lipid Composition during Saline Growth of the Fresh Water Cyanobacterium Synechococcus 6311

Growth of Synechococcus 6311 in the presence of 0.5 molar NaCl is accompanied by significant changes in membrane lipid composition. Upon transfer of the cells from a `low salt' (0.015 molar NaCl) to `high salt' (0.5 molar NaCl) growth medium at different stages of growth, a rapid decrease in palmitoleic acid (C16:1Δ9) content was accompanied by a concomitant increase in the amount of the two C18:1 acids (C18:1Δ9, C18:1Δ11), with the higher increase in oleic acid C18:1Δ9 content. These changes began to occur within the first hour after the sudden elevation of NaCl and progressed for about 72 hours. The percentage of palmitic acid (C16:0) and stearic acid (C18:0) remained almost unchanged in the same conditions. High salt-dependent changes within ratios of polar lipid classes also occurred within the first 72 hours of growth. The amount of monogalactosyl diacylglycerol (bilayer-destabilizing lipid) decreased and that of the digalactosyl diacylglycerol (bilayer-stabilizing lipid) increased. Consequently, in the three day old cells, the ratio of monogalactosyl diacylglycerol to digalactosyl diacylglycerol in the membranes of high salt-grown cells was about half of that in the membranes of low salt-grown cells. The total content of anionic lipids (phosphatidylglycerol and sulfoquinovosyl diacylglycerol) was always higher in the isolated membranes and the whole cells from high salt-grown cultures compared to that in the cells and membranes from low salt-grown cultures. All the observed rearrangements in the lipid environment occurred in both thylakoid and cytoplasmic membranes. Similar lipid composition changes, however, to a much lesser extent, were also observed in the aging, low salt-grown cultures. The observed changes in membrane fatty acids and lipids composition correlate with the alterations in electron and ion transport activities, and it is concluded that the rearrangement of the membrane lipid environment is an essential part of the process by which cells control membrane function and stability.     

发状念珠藻(发菜)细胞质膜的分离与性质分析

使用一种新方法首次从野生发菜(Nostoc flagelliforme Born.et Flah.)中分离得到细胞质膜并对其性质进行了分析,该方法的主要特点为联合使用细胞破碎仪和毛地黄皂甙对发菜细胞进行破碎.经过细胞破碎仪处理两次(80MPa)后,样品(20mg干重/mL)中的细胞可被毛地黄皂甙(3mg/mL)有效破碎,细胞质膜即可通过蔗糖密度梯度离心得以分离.纯化后的质膜,其吸收光谱中类胡萝卜素的3个吸收峰分别位于458、487和524 nm,另外一种叶绿素前体在673 nm处有少量吸收,质膜的荧光发射来自该叶绿素前体.通过变性电泳对其进行多肽组成分析,可分辨出30多条多肽,其中分子量为80、28、19和17 kD的多肽含量最高.其膜脂主要包含4种成分:单半乳糖甘油二酯(62.4%)、双半乳糖甘油二酯(18.9%)、硫代异鼠李糖甘油二酯(16.7%)和磷酯酰甘油(2.0%).膜脂酯酰基连接有棕榈酸(16:0)、十六碳烯酸(16:1[9])、硬脂酸(18:0)、油酸(18:1[9])、亚油酸(18:2[9,12])和亚麻酸(18:3[9,12,15])等六种脂肪酸,其中十六碳烯酸和亚麻酸为主要成分,分别占总脂肪酸含量的32.3%和34.4%.质膜中高含量的亚麻酸可能是发菜具有极强抗旱能力的一个重要因素.     

The effect of cadmium on lipid and fatty acid biosynthesis in tomato leaves

This research aims to examine the effect of cadmium uptake on lipid composition and fatty acid biosynthesis, in young leaves of tomato treated seedlings (Lycopersicon esculentum cv. Ibiza F1). Results in membrane lipids investigations revealed that high cadmium concentrations affect the main lipid classes, leading to strong changes in their composition and fatty acid content. Thus, the exposure of tomato plants to cadmium caused a concentration-related decrease in the unsaturated fatty acid content, resulting in a lower degree of fatty acid unsaturation. The level of lipid peroxides was significantly enhanced at high Cd concentrations. Studies of the lipid metabolism using radioactive labelling with [1-¹⁴C]acetate as a major precursor of lipid biosynthesis, showed that levels of radioactivity incorporation in total lipids as well as in all lipid classes were lowered by Cd doses. In total lipid fatty acids, [1-¹⁴C]acetate incorporation was reduced in tri-unsaturated fatty acids (C16:3 and C18:3); While it was enhanced in the palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0) and linoleic (C18:2) acids. [1-¹⁴C]acetate incorporation into C16:3 and C18:3 of galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] and some phospholipids [phosphatidylcholine (PC) and phosphatidylglycerol (PG)] was inhibited by Cd stress. Our results showed that in tomato plants, cadmium stress provoked an inhibition of polar lipid biosynthesis and reduced fatty acid desaturation process.     

Isolation and Characterization of the Cytoplasmic Membrane from the Terrestrial Cyanobacterium -Nostoc flagelliforme

Cytoplasmic membrane of Nostoc flagelliforme Born. et Flah. was isolated for the first time with a new method, the unique feature of which is the combined use of French pressure cell and digitonin to disrupt cells. After passed twice through French pressure cell (at 80 MPa), cells in sample (20 mg of dry weight/mL) were disrupted effectively by digitonin (3 mg/mL), and then the cytoplasmic membrane was isolated by density gradient centrifugation. The membrane contained carotenoids with absorption peaks at 458, 487 and 524 nm and a precursor of chlorophyll a with a minor peak at 673 nm. The fluorescence emission peaks of the membrane were emitted from the precursor of chlorophyll a. More than 30 polypeptides were detected in the membrane, in which the most obvious corresponded to the polypeptides with molecular mass of 80,28,19 and 17 kD. The membrane contained four types of glycerolipids: MGDG(62.4%), DGDG (18.9%), SQDG (16.7%) and PG (2.0%). 16:0, 16:1 [9], 18:0, 18:1 [9], 18:2 [9, 12] and 18:3 [9,12,15] fatty acids were determined in the membrane, in which 16:1 and 18:3 fatty acids were the main components, representing 32.3% and 34.4% of the total fatty acids respectively. High proportion of 18:3 fatty acid in the cytoplasmic membrane may be an important factor of N. flagelliforme in its remarkable drought-tolerant ability.     

The fatty acids of Trypanosoma vivax

A study was carried out to determine the lipid composition of the blood-stream form of the African trypanosome. Trypanosoma vivax. Data from thin layer chromatography showed that the major polar lipids were lysophosphatidylcholine, sphingomyelin, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and diphosphatidylglycerol. The major neutral lipids were sterol, monoacylglycerol, diacylglycerol, free fatty acid and triacyglycerol. 16:0, 18:0, 18:1 and 18:2 constituted the major fatty acids of both the polar and neutral lipid fractions. The work constituted the first detailed study on the fatty acid composition of this African trypanosome.     

BIOCHEMICAL COMPOSITION AND FATTY ACID CONTENT OF FILAMENTOUS NITROGEN-FIXING CYANOBACTERIA

The biochemical composition and fatty acid content of twelve strains of filamentous, heterocystous, nitrogen-fixing cyanobacteria have been determined. When grown under diazotrophic conditions, protein, carbohydrate, lipid, and nucleic acids comprised 37–52%, 16–38%, 8–13%, and 8–11% of the dry weight, respectively. The presence of a combined nitrogen source resulted in an increase in the protein content of the cells and a decrease in the levels of lipids and carbohydrates, although biomass productivity was not affected significantly. Biochemical composition also changed during culture growth, with the highest levels of proteins and lipids occurring as the culture entered stationary phase, whereas the highest levels of carbohydrate and nucleic acids were found during the exponential phase. Total fatty acid levels in the strains assayed ranged between 3 and 5.7% of the dry weight. With regard to fatty acid composition, all strains showed high levels of polyunsaturated fatty acids (PUFAs) and saturated fatty acids (SAFAs), with values of 24–45% and 31–52% of total fatty acids, respectively, whereas the levels of monounsaturated fatty acids (MUFAs) were in general lower (11– 32%). Palmitic acid (16:0) was the most prevalent SAFA, whereas palmitoleic (16:1n- 7) and oleic acid (18:1n-9) were the most abundant MUFAs in all the strains. Among PUFAs, γ-linolenic acid (GLA, 18:3n-6) was present at high levels (18% of total fatty acids) in Nostoc sp. (Chile) and at lower levels (3.6% of total fatty acids) in Anabaenopsis sp. The presence of GLA has not been previously reported in these genera of cyanobacteria. The rest of the strains exhibited high levels (12–35% of total fatty acids) of α-linolenic acid (ALA, 18:3n-3). Linoleic acid (18:2n-6) was also present at a substantial level in most of the strains. Eicosapentaenoic acid (EPA, 20:5n-3) was also detected in Nostoc sp. (Albufera). Some filamentous nitrogen-fixing cyanobacteria therefore represent potential sources of commercially interesting fatty acids.