Effects of CO2 and nitrogen supply on the biochemical composition of Ulva rigida with especial emphasis on lipid class analysis

Lipid class composition was analysed in the green macroalga Ulva rigida grown under normal (350 ppm) and high (10,000 ppm) CO₂ levels, and in nitrate saturated and nitrogen limited conditions. A new protocol for the extraction of lipids has been defined. Culture conditions altered the fate of assimilated carbon, and significant changes were observed in protein and total lipid content in particular. A CO₂-enriched atmosphere conditioned the effects of nitrogen limitation on lipid class composition, revealing deep qualitative changes in carbon metabolism. Triglycerides accumulated at high CO₂ and under nitrogen limitation, while chloroplast-related lipids showed an inverse response. Changes in phospholipids could be related to carbon availability as they did not respond to nitrogen limitation. The ratio sterols/acetone-mobile polar lipids followed a negative linear relation with the optimum quantum yield for photosynthetic electron transport (F_v/F_m), and was considered as an index of the «light status» of the cell. The specificity of the response of lipid classes to growth conditions in U. rigida emphasizes the potential role of lipid class analyses as a diagnostic tool for environmental stress.     

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.     

The Neutral Lipids of Paramecium tetraurelia: Changes with Culture Age and the Detection of Steryl Esters in Ciliary Membranes1

Neutral lipids, particularly triglycerides, accounted for the major decrease in the total lipid content in Paramecium cells that occurs with culture age. Sterols, triglycerides, and steryl esters were the major classes of neutral lipids in cells and isolated cilia. Free as well as high concentrations of esterified sterols were detected in purified ciliary membrane preparations. Stigmasterol and 7-dehydrostigmasterol were the major components of both free and esterified sterols of cells and cilia; however, when cholesterol was present in the growth medium, it was desaturated to 7-dehydrocholesterol and incorporated into cellular and ciliary lipids. Free fatty acids from cells and triglycerides from cells and cilia were low in polyunsaturated fatty acids and reflected the composition of fatty acids in the culture medium. An exception was the reduced concentration of stearate in triglycerides from whole cells. Greater than 50% of triglyceride fatty acids from cilia were saturated. The fatty acid compositions of cellular triglycerides and ciliary steryl esters did not change with culture age, but those of cellular steryl esters and ciliary triglycerides did change. In comparison with phospholipids, these neutral lipid fatty acid compositional changes were smaller. The sensitivity of these stigmasterol-containing cells to polyene antibiotics indicated that they were killed by nystatin > filipin > amphotericin B. The unexpected finding of high concentrations of steryl esters in ciliary membrane preparations is discussed.     

EFFECT OF GROWTH AND LIGHT/DARK CYCLES ON DIATOM LIPID CONTENT AND COMPOSITION1

Total extractable lipid (TEL) and lipid composition were studied throughout the growth cycle in three freshwater diatoms-Cyclotella meneghiniana Kütz., Melosira varians C. A. Ag., and Stephanodiscus binderanus (Kütz.) Krieg under three light regimes (16:8 h LD, 20:4 h LD, and 12:12 h LD) at 20°C. Two of the diatoms demonstrated strong daylength preferences for growth; C. meneghiniana grew best under long-day (20: 4-h LD) conditions, whereas S. binderanus grew best under short-day (12:12-h LD) conditions. The lipid composition of the diatoms was similar throughout the growth cycle. Aged (2-month-old) cells were high in total lipid and triacylglycerols. Before the onset of active growth and during the early part of active growth, there was a reduction in total neutral lipids, primarily triacylglycerols, and an increase in all polar lipids, including chlorophyll a, acetone-mobile polar lipids, and phospholipids. While cell numbers were still increasing, triacylglycerols increased and polar lipids decreased to levels near those found in aged cultures, Results suggest that increased triacylglycerol content of freshwater diatoms is not necessarily indicative of senescent populations.     

Dimorphism-associated variations in the lipid composition of Candida albicans

Yeast and mycelial forms of Candida albicans ATCC 10231, growing together in 12 h and in 96 h cultures, were separated and their lipids were extracted and characterized. The total lipid content of the yeast forms was always lower than that of the mycelial forms. In 12 h cultures the lipids from the two morphological forms consisted mainly of polar compounds, viz, phospholipids and glycolipids. In 96 h cultures both the yeast and mycelial forms accumulated substantial amounts of apolar compounds, mainly steryl esters and triacylglycerols. The mycelial forms were more active than the yeast forms in this respect. Major differences in the lipid composition between the two morphological forms involved the contents of sterols and complex lipids that contain sterols. As a rule, the yeast lipids contained much larger proportions of free sterols than the mycelial lipids. However, the mycelial lipids contained several times more sterols than the yeast forms but bound as steryl glycosides, esterified steryl glycosides and steryl esters. Steryl glycosides and esterified steryl glycosides occurred in yeast lipids only in traces, if at all. The major steryl glycoside in the mycelial forms was unequivocally identified as cholesteryl mannoside. At both phases of growth the apolar and polar lipid fractions from the mycelial forms contained higher levels of polyunsaturated fatty acids (18:2 and 18:3) but lower levels of oleic acid (18:1) than the corresponding fractions from the yeast forms. The lipid content and composition of 12 h and 96 h yeast and mycelial forms of C. albicans KCCC 14172, a clinical isolate, were almost identical with those of C. albicans ATCC 10231.     

Lipids of Rhizopus arrhizus Fischer

The lipids of Rhizopus arrhizus Fischer mycelia and sporangiospores were extracted, isolated, and separated by thin-layer, liquid, and gas chromatography. Structural confirmations of the compounds were made by a gas chromatographmass spectrometer combination. The n-heptane fraction contained squalene (1%) as a major hydrocarbon constituent. Other major lipid classes detected were free fatty acids, naturally occurring methyl esters of fatty acids, triglycerides, sterols, and polar lipids. The polar lipids (44.4%) were found in the highest concentrations, and the triglycerides (22.1%), sterols (16.7%), and free fatty acids (11.7%) were present in lesser concentrations. This is the first report of naturally occuring methyl esters of long-chain fatty acids being present in fungal mycelium. There appears to be a preference for incorporation of unsaturated acids into the complex lipids, with the exception of the triglycerides. The major saturated fatty acids in the mycelium were palmitic (C(16)) and arachidic (C(20)), whereas the major unsaturated acids were oleic (C(18:1)) and linoleic (C(18:2)), respectively.     

Lipids associated with microconidial differentiation in a mutant ofNeurospora crassa

Thepeach-fluffy-cot mutant ofNeurospora crassa produces neither macroconidia nor ascospores but does differentiate microconidia after a defined length of time. Changes in the composition of sterols, sterol esters, triglycerides, free fatty acids, and phospholipids were followed during vegetative growth and differentiation of microconidia. The changes in free sterols before and during microconidial differentiation indicate a change in lipid metabolism associated with differentiation. Free sterols and sterol esters accumulated in the developing microconidia, but decreased rapidly during microconidial maturation. The fatty acid components remained relatively unchanged except for a significant increase in linoleic acid. The linoleic acid change might be associated with the development of microconidia or it might simply be a reflection of the NADP-deficiency common in many morphological mutants ofN. crassa.     

A survey of polar and nonpolar lipids from epidermis and epidermal appendages of the chicken (Gallus domesticus)

Total lipid was extracted from chicken (Gallus domesticus) epidermis, leg scale, claws, feathers and preen glands and analyzed by quantitative thin-layer chromatography. All of the tissue lipids contained large proportions of wax diesters, triglycerides, and free sterols and variable proportions of phospholipids, steryl esters and free fatty acids. All of the keratinized tissues, but not the preen gland, contained ceramides, acylceramides and cholesteryl sulfate. Acylglucosylceramides were found only in full thickness epidermis. Glucosylsterols and acylglucosylsterols were found in the keratinized tissues, and may be of significance in the evolutionary history of the epidermal water barrier.     

The lipid content of cell walls obtained from juvenile,yeast-like and filamentous cells ofCandida albicans

Purified cell walls ofCandida albicans obtained from juvenile cells, mature yeast-like cells and filamentous cells were analyzed for their lipid components. Chloroform: methanol (2:1 v v) extraction of the acetone-treated dried cell walls indicated the total lipid content to be 2.1% of the dry weight of the juvenile cell walls, 1.8% of the mature yeast-like cell walls and 4.5% of the filamentous cell walls. Separation of the chloroform: methanol extractable fraction through a silicie acid column and quantitative determination of the fractions showed significant amounts of sterol esters, triglycerides, sterols, free fatty acids, and phospholipids in these extracts. Following acetone extraction sterols were shown to constitute a greater percentage of the cell wall of juvenile cells than mature cells. Thin-layer chromatography separated the acetone-extractable lipids into at least four components. Diethyl ether extracts of the cell walls indicated the presence of small amounts of glycerol phospholipids in the cell walls of juvenile and mature yeast cells. Boiling 95% ethanol also removed a small lipid fraction from the cell walls of both juvenile and mature yeast which could include sphingosine phosphatides or glycosides.     

LIPID COMPOSITION OF THE BROWN ALGA FUCUS VESICULOSUS1,2

The lipids of the brown alga Fucus vesiculosus consist of approximately 3.6% hydrocarbons (including carotenes) and sterol esters, 11.8% triglycerides, 4.2% free fatty acids, 10.6% sterols, 15.1% chlorophylls and xanthophylls, 29.9% glycolipids, and 6.5% phospholipids. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, and phosphatidylinositol appear to be present and phosphatidylcholine is absent.     

Evidence for a Composite State of an F′his,gnd Element and a Cryptic Plasmid in a Derivative of Salmonella typhimurium LT2

The zoospores of Blastocladiella emersonii, when derived from cultures grown on solid media, contain about 11% total lipid. This lipid was separated chromatographically on silicic acid into neutral lipid (46.6%), glycolipid (15.8%), and phospholipid (37.6%). Each class was fractionated further on columns of silicic acid, Florisil, or diethylaminoethyl-cellulose, and monitored by thin-layer chromatography. Triglycerides were the major neutral lipids, mono- and diglycosyldiglycerides were the major glycolipids, and phosphatidylcholine and phosphatidylethanolamine were the major phospholipids. Other neutral lipids and phospholipids detected were: hydrocarbons, free fatty acids, free sterols, sterol esters, diglycerides, monoglycerides, lysophosphatidylcholine, lysophosphatidylethanolamine, phosphatidic acid, phosphatidylserine, and phosphatidylinositol. Palmitic, palmitoleic, stearic, oleic, gamma-linolenic, and arachidonic acids were the most frequently occurring fatty acids. When B. emersonii was grown in (14)C-labeled liquid media, lipid again accounted for 11% of both mature plants and zoospores released from them. The composition of the lipid extracted from such plants and spores was also the same; however, it differed markedly from that of the lipid in spores harvested from solid media, consisting of 28.3% neutral lipid, 12.0% glycolipid, and 59.7% phospholipid. The major lipids were again triglycerides for neutral lipids, mono- and diglycosyldiglycerides for glycolipids, and phosphatidyl choline and phosphatidylethanolamine for phospholipids.     

The effects of nitrogen fertilisation and elevated CO2 on the lipid biosynthesis and carbon isotopic discrimination in birch seedlings (Betula pendula)

The effects of nitrogen (N) fertilisation and elevated [CO₂] on lipid biosynthesis and carbon isotope discrimination in birch (Betula pendula Roth.) transplants were evaluated using seedlings grown with and without N fertiliser, and under two concentrations of atmospheric CO₂ (ambient and ambient+250 μmol mol^-1) in solar dome systems. N fertilisation decreased n-fatty acid chain length (18:0/16:0) and the ratios of α-linolenate (18:2)/linoleate (18:1), whereas elevated [CO₂] showed little effect on n-fatty acid chain length, but decreased the unsaturation (18:2+18:1)/18:0. Both N fertilisation and elevated [CO₂] increased the quantity of leaf wax n-alkanes, whilst reducing that of n-alkanols by 20–50%, but had no simple response in fatty acid concentrations. ¹³C enrichment by 1–2.5‰ under N fertilisation was observed, and can be attributed to both reduced leaf conductance and increased photosynthetic consumption of CO₂. Individual n-alkyl lipids of different chain length show consistent pattern of δ¹³C values within each homologue, but are in general 5–8‰ more depleted in ¹³C than the bulk tissues. Niether nitrogen fertilisation and elevated CO₂ influenced the relationship between carbon isotope discrimination of the bulk tissue and the individual lipids. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of weak constant magnetic field on the composition and content of lipids in radish seedlings at various temperatures

We studied the effects of weak permanent homogenous hirizontal magnetic field (PMF) (400 A/m) on the composition and content of lipids and composition of their fatty acids (FAs) in radish (Raphanus sativus L. var. radicula D.C., cv. Rosovo-krashyi s belym konchikom) seedlings at temperatures of 20 and 10°C. We compared lipid composition and content in seedlings at the phase of developed cotyledons (20°C, 5-day-old, and 10°C, 8-day-old seedlings) under low light and in darkness with the lipid composition and content in dry seeds. The seedlings grown in geomagnetic field (GMF) served as a control. In dry seeds, about 99% of total lipids comprised neutral lipids (NL) and only 1% were polar lipids (PL). Triacylglycerols predominated among NL comprising 93% of total seed lipids. During seed germination, NLs were consumed and PL were produced: the amount of glycolipids increased in control by 3.5–5 times and the amount of phospholipis, by 1.5–2 times.In the light at 20°C, PMF suppressed the formation of PL (by 18%), whereas in darkness, it stimulated it approximately by 80% as compared with control. In the light at 10°C, PMF slightly stimulated PL formation; in darkness, it did not almost affect their synthesis. In all treatments, PMF increased the ratio of phospholipids to sterols by 30–100%. Among FA, PMF exerted the strongest effect on the content of erucic acid: it increased in the light and in darkness at 20°C approximately by 25% and decreased at 10°C in the light by 13%. PMF behaved as a correction factor affecting lipid metabolism on the background of light and temperature action.     

Lipid and sterol composition of the pollen of the west african oilpalm, Elaeis guineensis

The lipid classes, fatty acid methyl esters and the sterols of oilpalm pollen were analysed. The neutral lipid fraction consisted of triglycerides, esterified and free sterols and trace amounts of hydrocarbons. Monogalactosyl and digalactosyl diglycerides, phosphatidyl choline, phosphatidyl inositol and phosphatidyl ethanolamine represented the polar lipids. The major fatty acids were linoleic, palmitic and linolenic acids together with small to trace amounts of oleic, stearic, arachidic, myristic, lauric, palmitoleic and margaric acids. Unsaturated fatty acids predominated over saturated ones in the ratio of 3:2. The 4-desmethyl sterols were the major phytosterols in the free form but they constituted a lower proportion of the sterols in the esterified state. 28-Isofucosterol was isolated and characterized as the principal sterol.     

Comparative studies on the lipid composition of some digenetic trematodes.

Yusufi A. N. K. &; Siddiqi A. H. 1976. Comparative studies on the lipid composition of some digenetic trematodes. International Journal for Parasitology6: 5–8. Neutral lipids and phospholipids of six digenetic trematodes, Cotylophoron cotylophorum, Gastrothylax crumenifer and Gigantocotyle explanatum from water buffalo, Echinostoma malayanum and Fasciolopsis buski from pig and Isoparorchis hypselobagri from cat-fish were analyzed. Total lipid concentrations in trematodes varied considerably irrespective of their hosts and habitats. While triglycerides were the major components in all species, considerable amounts of phospholipids and free fatty acids were present in all species. Cholesterol was minimum (4–9%) in more or less all species, except in F. buski, where cholesterol, phospholipids and triglycerides constituted 13–14% and free fatty acids around 7%. Among phospholipids, choline and ethanolamine phosphatides were major polar lipids. Sphingomyelin and cardiolipin were present as small fractions and lysophosphatidylcholine was evenly distributed among all the species (9–12%) except in F. buski, which contained a little higher content (15%).     

高大气CO2浓度下氮素对小麦叶片光能利用的影响

关于氮素对高大气CO₂浓度下C₃植物光合作用适应现象的调节机理已有较为深入的研究, 但对其光合作用适应现象的光合能量转化和分配机制缺乏系统分析。该文以大气CO₂浓度和施氮量为处理手段, 通过测定小麦(Triticum aestivum)抽穗期叶片的光合作用-胞间CO₂浓度响应曲线以及荧光动力学参数来测算光合电子传递速率和分配去向, 研究了长期高大气CO₂浓度下小麦叶片光合电子传递和分配对施氮量的响应。结果表明, 与正常大气CO₂浓度处理相比, 高大气CO₂浓度下小麦叶片较多的激发能以热量的形式耗散, 增施氮素可使更多的激发能向光化学反应方向的分配, 降低光合能量的热耗散速率; 大气CO₂浓度升高后小麦叶片光化学淬灭系数无明显变化, 高氮叶片的非光化学猝灭降低而低氮叶片明显升高, 施氮促进PSII反应中心的开放比例, 降低光能的热耗散; 高大气CO₂浓度下高氮叶片通过PSII反应中心的光合电子传递速率(J_F)较高, 而且参与光呼吸的非环式电子流速率(J₀)显著降低, 较正常大气CO₂浓度处理的高氮叶片下降了88.40%, 光合速率增加46.47%; 高大气CO₂浓度下小麦叶片J_F-J₀升高而J₀/J_F显著下降, 光呼吸耗能被抑制, 更多的光合电子分配至光合还原过程。因此, 大气CO₂浓度增高条件下, 小麦叶片激发能的热耗散速率增加, 但增施氮素后小麦叶片PSII反应中心开放比例提高, 光化学速率增加, 进入PSII反应中心的电子流速率明显升高, 光呼吸作用被抑制, 光合电子较多地进入光化学过程, 这可能是高氮条件下光合作用适应性下调被缓解的一个原因。     

Lipid and hydrocarbon production byBotryococcus spp. under nitrogen limitation and anaerobiosis

The production of lipids and hydrocarbons in batch cultures of the algaeBotryococcus braunii andB. protuberans has been studied with respect to nitrogen limitation under aerobic and anaerobic conditions. Nitrogen deficiency significantly decreased the dry weight, chlorophylla and protein contents but the amounts of carotenoids, carbohydrates and lipids increased in both the species. Nitrogen starvation gave a 1.6-fold increase in lipid content. Anaerobiosis under nitrogen deficient conditions gave greater lipid production than anaerobiosis in nitrogen supplemented medium. Under nitrogen deficiency, the hydrocarbon fraction increased and the polar lipids decreased. Anaerobiosis induced hydrocarbon synthesis more significantly than nitrogen deficiency but decreased other non-polar and polar lipids.     

Assessment of <Emphasis Type="Italic">Nannochloropsis gaditana</Emphasis> growth and lipid accumulation with increased inorganic carbon delivery

Algal biomass refineries for sustainable transportation fuels, in particular biodiesel, will benefit from algal strain enhancements to improve biomass and lipid productivity. Specifically, the supply of inorganic carbon to microalgal cultures represents an area of great interest due to the potential for improved growth of microalgae and the possibility for incorporation with CO₂ mitigation processes. Combinations of bicarbonate (HCO₃^?) salt addition and application of CO₂ to control pH have shown compelling increases in growth rate and lipid productivity of fresh water algae. Here, focus was placed on the marine organism, Nannochloropsis gaditana, to investigate growth and lipid accumulation under various strategies of enhanced inorganic carbon supply. Three gas application strategies were investigated: continuous sparging of atmospheric air, continuous sparging of 5% CO₂ during light hours until nitrogen depletion, and continuous sparging of atmospheric air supplemented with 5% CO₂ for pH control between 8.0 and 8.3. These gas sparging schemes were combined with addition of low concentrations (5 mM) of sodium bicarbonate at inoculation and high concentration (50 mM) of sodium bicarbonate amendments just prior to nitrogen depletion. The optimum scenario observed for growth of N. gaditana under these inorganic carbon conditions was controlling pH with 5% CO₂ on demand, which increased both growth rate and lipid accumulation. Fatty acid methyl esters were primarily comprised of C16:0 (palmitic) and C16:1 (palmitoleic) aliphatic chains. Additionally, the use of high concentration (50 mM) of bicarbonate amendments further improved lipid content (up to 48.6%) under nitrogen deplete conditions when paired with pH-controlled strategies.     

Lipids of the Green Alga BotryococcusCultured in a Batch Mode

The lipid fraction of the green alga Botryococcuscultured in a batch mode was found to contain polar lipids (more than 50% of the total lipids), di- and triacylglycerols, sterols and their esters, free fatty acids, and hydrocarbons. In aging culture, the content of polar lipids somewhat decreased and that of triacylglycerols increased by more than four times. The content of hydrocarbons in the algal biomass did not exceed 0.9% and depended little on the culture age. Intracellular lipids contained saturated and unsaturated (mono-, di-, and trienoic) fatty acids. The maximum content of C_{16 : 3}and -C_{18 : 3}fatty acids (up to 35% of the total fatty acids) was detected in the phase of active growth. The extracellular and intracellular lipids of the alga differed in the proportion of particular lipids and in the fatty acid pattern.     

Insights into unique physiological features of neutral lipids in Apicomplexa: from storage to potential mediation in parasite metabolic activities

The fast intracellular multiplication of apicomplexan parasites including Toxoplasma and Plasmodium, requires large amounts of lipids necessary for the membrane biogenesis of new progenies. Hence, the study of lipids is fundamental in order to understand the biology and pathogenesis of these deadly organisms. Much has been reported on the importance of polar lipids, e.g. phospholipids in Plasmodium. Comparatively, little attention has been paid to the metabolism of neutral lipids, including sterols, steryl esters and acylglycerols. In eukaryotic cells, free sterols are membrane components whereas steryl esters and acylglycerols are stored in cytosolic lipid inclusions. The first part of this review describes the recent advances in neutral lipid synthesis and storage in Toxoplasma and Plasmodium. New potential pharmacological targets in the pathways producing neutral lipids are outlined. In addition to lipid bodies, Apicomplexa contain unique secretory organelles involved in parasite invasion named rhoptries. These compartments appear to sequester most of the cholesterol found in the exocytic pathway. The second part of the review focuses on rhoptry cholesterol and its potential roles in the biogenesis, structural organisation and function of these unique organelles among eukaryotes.