Effect of exogenous fatty acids on growth,membrane fluidity,and phospholipid fatty acid composition in yeast

The growth response of a double-mutant fatty acid auxotroph of yeast Saccharomyces cerevisiae to exogenous saturated fatty acids of a homologous series from 12:0 to 16:0, each supplied with oleate, linoleate, linolenate, or cis-Δ¹¹- eicosenoate, cannot be explained in terms of the efficiency of incorporation of the fatty acids into phospholipids or alteration of membrane fluidity. There is, however, a negative correlation between growth and levels of 12:0 plus 13:0 in phospholipids, as well as a positive correlation between growth and levels of 14:0, 1 5:0, and 1 6:0. We, therefore, conclude that the predominant factor in these phospholipid fatty acyl chain modifications is maintenance of an optimal concentration of C14:0 through C16:0 in phospholipids of this organism.     

Isolation and characterization of psychrophilic yeasts producing cold-adapted pectinolytic enzymes

AIMS: The present study was conducted to screen for psychrophilic yeasts that are able to degrade pectin compounds at low temperature, and to examine the cold-active pectinolytic enzymes produced by the isolated psychrophilic yeasts. METHODS AND RESULTS: Psychrophilic yeasts, which grow on pectin as a sole carbon source, pectinolytic-psychrophilic yeast (PPY) strains PPY-3, 4, 5 and 6, were isolated from soil from Abashiri (Hokkaido, Japan). The sequences of 28S rDNA D1/D2 of strains PPY-3 and 4 indicated a taxonomic affiliation to Cryptococcus cylindricus and Mrakia frigida, respectively, strains PPY-5 and 6 belonged to Cystofilobasidium capitatum. The isolated strains were able to grow on pectin at below 5 degrees C, and showed the activities of several cold-active pectinolytic enzymes. CONCLUSION: The findings of this study indicate the possibility that the isolated strains produce novel pectinolytic enzymes that are able to degrade pectin compounds at low temperature. Significance and Impact of the Study: It is possible that the cold-active pectinolytic enzymes from the isolated strains can be applied to the food industry, e.g. the clarification of fruit juice below 5 degrees C.     

不同饵料对卤虫生长、总脂含量及脂肪酸组成的影响

为了提高养殖卤虫的饵料营养价值,了解其不同生长阶段营养成分变化情况,采用单因子试验研究了8种饵料（三角褐指藻、小球藻、微绿球藻、酵母液、三角褐指藻＋小球藻＋微绿球藻、三角褐指藻＋酵母液、小球藻＋酵母液和微绿球藻＋酵母液）对卤虫生长、总脂含量及脂肪酸组成的影响,结果表明：不同饵料种类对卤虫生长、总脂含量及脂肪酸组成的影响显著（P＜0.05）,增长率,以三角褐指藻＋酵母液最优;总脂含量、以三角褐指藻最优（19.67%）,除酵母液外,与其它饵料相差不显著（P＞0.05）;脂肪酸组成效果,以微绿球藻组最优（EPA：18.01%,DNA：0.55%,（n-3）HUFA：19.08%）,与三角褐指藻组相差不大（P＞0.05）,显著高于其它各组（P＞0.05）.同时以三角褐指藻为饵料,研究了卤虫不同生长阶段（体长2、4、6、8、10 mm）总脂含量、脂肪酸组成变化,结果表明：卤虫体长2～10 mm总脂含量为14.27%～20.93%,随体长的增长降低;EPA、DHA及（n-3）HUFA的含量,均随体长的增长降低,EPA含量为：10.47%～20.77%,DNA含量为：0～0.70%,（n-3）HUFA含量为：10.85%～22.01%.结论认为,卤虫以三角褐指藻或三角褐指藻＋酵母液为饵料培养营养价值最佳,其体长小于6 mm营养价值较佳.     

光照强度对四株海洋绿藻总脂含量和脂肪酸组成的影响

采用f/2培养基,在3000lx,5000lx,8000lx光照强度时对杆状裂丝藻(Stichococcus bacillaris,MACC(中国海洋大学微藻种质库)/C19)和3株小球藻(Chlorellasp.MACC/C95,MACC/C97和MACC/C102)等4株海洋绿藻的总脂含量及脂肪酸组成进行了研究。单因子方差分析结果表明,光照强度对4株海洋绿藻的相对生长率、EPA(二十碳五烯酸,20∶5(n-3))含量及PUFA(多不饱和脂肪酸)总量,C19、C97和C102的脂肪含量和SFA(饱和脂肪酸)总量,C19、C95和C102的MUFA(单不饱和脂肪酸)总量均有显著影响(P0.05)。C19和C95的总脂含量随光照强度的增加总体呈降低趋势,C97和C102的总脂含量则随光照强度的升高而明显升高。C19的EPA含量随光照强度的增加呈现低-高-低趋势,C95在中低光照强度下EPA含量较高,C97和C102的EPA含量则随光照强度的增加而明显降低,4株绿藻的AA(花生四烯酸,20∶4(n-6))含量和PUFA总量均随光照强度的增加而降低。多重比较结果表明:C19在高光照强度(8000lx)时总脂含量显著低于其它各组,低光照强度(3000lx)和中光照强度(5000lx)处理间没有显著性差异(12.9%—12.7%),C97和C102则分别在高光照强度时总脂含量显著高于其它各处理(分别为40.6%和33.3%)。C19的EPA含量在中光照强度水平显著高于其它处理(12.7%),C97和C102的EPA含量分别在低光照强度水平显著高于其它处理(分别为12.0%和10.5%),C95的EPA含量在高光照强度水平显著低于其它处理,低光照强度和中光照强度处理间没有显著性差异(14.0%—14.7%);C19和C95的PUFA总量均在高光照强度水平显著低于其它处理,在低光照强度和中光照强度处理间没有显著性差异(分别为19.1%—19.4%和21.3%—21.3%),C97和C102的PUFA总量均在低光照强度水平显著高于其它处理(分别为19.2%和18.9%)。4株绿藻的主要脂肪酸成份为14∶0、16∶0、16∶1(n-7)、16∶4(n-3)、18∶1(n-9)、18∶3(n-3)、20∶4(n-6)和EPA。     

Nonesterified fatty acids and lipid peroxidation

Oxygen free radicals damage cells through peroxidation of membrane lipids. Gastrointestinal mucosal membranes were found to be resistant to in vitro lipid peroxidation as judged by malonaldehyde and conjugated diene production and arachidonic acid depletion. The factor responsible for this in this membrane was isolated and chemically characterised as the nonesterified fatty acids (NEFA), specifically monounsaturated fatty acid, oleic acid. Authentic fatty acids when tested in vitro using liver microsomes showed similar inhibition. The possible mechanism by which NEFA inhibit peroxidation is through iron chelation and iron-fatty acid complex is incapable of inducing peroxidation. Free radicals generated independent of iron was found to induce peroxidaton of mucosal membranes. Gastrointestinal mucosal membranes were found to contain unusually large amount of NEFA. Circulating albumin is known to contain NEFA which was found to inhibit iron induced peroxidation whereas fatty acid free albumin did not have any effect. Addition of individual fatty acids to this albumin restored its inhibitory capacity among which monounsaturated fatty acids were more effective. These studies have shown that iron induced lipid peroxidation damage is prevented by the presence of nonesterified fatty acids.     

Lead-induced tissue fatty acid alterations and lipid peroxidation

Previous work showed that dietary lead (Pb) increases the relative concentration of arachidonic acid (20∶4) as a percentage of total fatty acids, and decreases the relative proportion of linoleic acid (18∶2) to arachidonic acid (18∶2/20∶4) in chick liver, serum, and erythrocyte membranes. The present investigation was undertaken to examine the time-course and magnitude of the fatty acid alterations with increasing dietary Pb levels. We also examined the effects of Pb on the fatty acid composition and lipid peroxide content of hepatic subcellular organelles. In Exp. 1, chicks were fed diets containing 0, 62.5, 125, 250, 500, or 1000 ppm added Pb (as Pb acetate trihydrate) from 1 to 21 d of age. After 21 d, no growth effects were observed; however, Pb lowered the 18∶2/20∶4 ratio and increased 20∶4 concentration in total liver and serum lipids, and in total hepatic phospholipids in a dose-dependent manner. Hepatic mitochondrial membrane fatty acids were not altered, nor was there any increase in hepatic lipid peroxidation. In Exp. 2, chicks were fed diets containing 0, 500, 1000, or 2000 ppm added Pb from 1 to 21 or 22 d of age. Pb depressed growth in a dose-dependent manner. In addition, Pb lowered the 18∶2/20∶4 ratio and increased 20∶4 concentration in total liver lipids and in hepatic mitochondrial and microsomal membranes in a dose-dependent manner. Total hepatic lipid peroxidation was increased over control values by 1000 ppm Pb, and hepatic microsomal lipid peroxidation was increased by dietary Pb levels of 1000 and 2000 ppm. In Exp. 3, body weight, hepatic microsomal lipid peroxidation, and fatty acid composition were determined in 4-, 9-, 14-, 18-, and 23-d-old chicks fed 0 or 1500 ppm added Pb. Body weights of Pb-treated chicks were significantly lower than those of control chicks by day 18. Microsomal 20∶4 concentration and peroxidation increased, and the 18∶2/20∶4 ratio decreased with age in both groups, but the changes were of greater magnitude in the Pb-treated chicks. The results suggest that some of the manifestations of Pb toxicity may be a reflection of increased concentration of 20∶4 in specific membranes. Further, since the Pb-induced alterations in fatty acid composition were noted in the absence of any growth depression, we propose that fatty acid composition is more sensitive than growth rate to the presence of lead in the diet.     

Effect of oilseed type on milk fatty acid composition of individual cows,and also bulk tank milk fatty acid composition from commercial farms

Supplementing dairy cow diets with oilseed preparations has been shown to replace milk saturated fatty acids (SFA) with mono- and/or polyunsaturated fatty acids (MUFA, PUFA), which may reduce risk factors associated with cardio-metabolic diseases in humans consuming milk and dairy products. Previous studies demonstrating this are largely detailed, highly controlled experiments involving small numbers of animals, but in order to transfer this feeding strategy to commercial situations further studies are required involving whole herds varying in management practices. In experiment 1, three oilseed supplements (extruded linseed (EL), calcium salts of palm and linseed oil (CPLO) and milled rapeseed (MR)) were included in grass silage-based diets formulated to provide cows with ~350 g oil/day, and compared with a negative control (Control) diet containing no supplemental fat, and a positive control diet containing 350 g/cow per day oil as calcium salt of palm oil distillate (CPO). Diets were fed for 28-day periods in a 5×4 Latin Square design, and milk production, composition and fatty acid (FA) profile were analysed at the end of each period. Compared with Control, all lipid supplemented diets decreased milk fat SFA concentration by an average of 3.5 g/100 g FA, by replacement with both cis- and trans-MUFA/PUFA. Compared with CPO, only CPLO and MR resulted in lower milk SFA concentrations. In experiment 2, 24 commercial dairy farms (average herd size±SEM 191±19.3) from the south west of the United Kingdom were recruited and for a 1 month period asked to supplement their herd diets with either CPO, EL, CPLO or MR at the same inclusion level as the first study. Bulk tank milk was analysed weekly to determine FA concentration by Fourier Transform mid-IR spectroscopy prediction. After 4 weeks, EL, CPLO and MR all decreased herd milk SFA and increased MUFA to a similar extent (average −3.4 and +2.4 g/100 g FA, respectively) when compared with CPO. Differing responses observed between experiments 1 and 2 may be due in part to variations in farm management conditions (including basal diet) in experiment 2. This study demonstrates the importance of applying experimental research into commercial practice where variations in background conditions can augment different effects to those obtained under controlled conditions.     

Efficacy of extraction methods for lipid and fatty acid composition from fungal cultures

The efficacy of three extraction methods for determining the lipid and fatty acid composition of six fungal cultures was studied. The extraction methods were: chloroform/methanol (2:1), hexane/isopropanol (3:2) and Soxhlet extraction by using hexane. The total lipid and fatty acid composition varied in fungal cultures depending on the extraction conditions. Of the three methods, chloroform/methanol (2:1) was found to be the best for extraction of lipid and fatty acids from fungal cultures.     

Effect of weight at slaughter and breed on beef intramuscular lipid classes and fatty acid profile

The effect of slaughter weight and breed on the composition of intramuscular fat (IMF) of seven Spanish cattle breeds was studied. Lipid classes and fatty acids were evaluated in young bulls of seven local Spanish cattle breeds, Asturiana, Avileña, Morucha, Parda Alpina, Pirenaica, Retinta and Rubia Gallega, slaughtered at a live weight of 320 kg (veal type) and 550 kg (yearling bull type). Higher slaughter weight and early maturating breeds produced higher IMF content in the longissimus muscle (P < 0.001), which was linked to a reduction in phospholipids, monoglycerides, diglycerides, cholesterol and free-fatty acids content, but an increase in triacylglycerols. Besides, heavier animals displayed a higher percentage of saturated and monounsaturated fatty acids (MUFA), but a lower polyunsaturated fatty acids (PUFA) percentage (P < 0.001). The increase in triglycerides (TG), saturated fatty acids (SFA) and MUFA illustrates the increasing importance of lipid storage as fattening proceeds and the acquisition of ruminal functionality. The feeding system based on cereals had a strong influence on the fatty acid profile, giving the studied beef a relatively high PUFA/SFA and n-6/n-3 ratios.     

High-throughput analysis of fatty acid composition of plasma glycerophospholipids

Plasma FA composition, a marker of FA status and dietary intake, is associated with health outcomes on a short- and long-term basis. Detailed investigation of the relationships between plasma FA composition and health requires the analysis of large numbers of samples, but manual sample preparation is very cumbersome and time consuming. We developed a high-throughput method for the analysis of FAs in plasma glycerophospholipids (GPs) with increased sensitivity. Sample preparation requires two simple steps: protein precipitation and subsequent base catalyzed methyl ester synthesis. Analysis of GP FAs is performed by gas chromatography. Coefficients of variation for FAs contributing more than 1% to total FAs are below 4%. Compared with the established reference method, results of the new method show good agreement and very good correlations (r > 0.9). The new method reduces the manual workload to about 10% of the reference method. Only 100 µl plasma volume is needed, which allows for the analysis of samples from infants. The method is well suitable for application in large clinical trials and epidemiological studies.     

5株新分离海洋硅藻总脂和脂肪酸组成的比较研究

从浙江渔山列岛、朱家尖海域拖网采集浮游植物,采用平板分离法和水滴分离法分离、纯化出5株硅藻,用MAV培养基进行培养,采用Bligh—Dyer法和气相色谱-质谱法,对5株海洋硅藻的总脂及脂肪酸组成进行了分析比较。结果表明：在水温17—25℃,盐度25,自然光照,不充气培养条件下,5株海洋硅藻的总脂含量为15．14％-28．07％,除成对海链藻（Thalassiosirabinata）外,大龙骨藻（Tropidoneismaxima）、咖啡双眉藻（Amphoracoffeaeformis）、曼氏骨奈藻SM-2012—1（Skeletonemamunzelii）、曼氏骨条藻SM-2012-2（Skeletonemamunzelii）的总脂含量均超过其干重的20％。除咖啡双眉藻的20：4n_6含量高于20：5n4外,其它4株硅藻的20：5n．3在脂肪酸组成中含量较高,达22．04％-27．74％;5株硅藻中C18系列脂肪酸含量较低,为0．13％-7．6％;咖啡双眉藻除外的其它4株硅藻均舍有一定量的22：6n-3（2．40％-3．45％）。最终选出大龙骨藻（Tropidoneis maxima）、曼氏骨条藻SM-2012-1（Skeletonemamunzelii）、曼氏骨条藻SM-2012-2（Skeletonemamunzelii）具有开发的潜能。     

Changes in fatty acid composition of lipid classes in developing mustard seed

Maturation of mustard (Sinapis alba) seed proceeds with a sharp decrease in the amounts of palmitic and linoleic acids in the total lipids up to 6 weeks after flowering (WAF). Concomitantly, the concentration of oleic acid increases, reaching a plateau at 4 WAF, which is followed by chain elongation of oleic acid to gadoleic and erucic acids. Compositional changes in constituent fatty acids of individual lipid classes indicate that the very long-chain monounsaturated fatty acids (C₂₀ and C₂₂), as opposed to common long-chain fatty acids (C₁₆ and C₁₈), are metabolized to triacylglycerols mainly by esterification to preformed diacylglycerols and monoacylglycerols, rather than via esterification to glycerol-3-phosphate or lysophosphatidic acids.     

Changes in sugar content and fatty acid composition of in vitro sugar beet shoots after cold acclimation: influence on survival after cryopreservation

To cryopreserve sugar beet shoot tips using an encapsulation-dehydration technique, cold hardening of in vitro plants was needed to obtain high survival rates after freezing. Cold acclimation not only enhanced dehydration and freezing tolerance, but also induced several changes in sugar beet shoots. Plants contained greater amounts of sucrose, D-glucose and D-fructose and the fatty acid composition of lipids changed. Furthermore, the unsaturation level of membrane lipids, estimated by the (C_18:2 + C_18:1)/C_16:0 ratio, increased after cold hardening. These changes were correlated with better survival rates after cryopreservation.     

The value of lipid composition in the taxonomy of the Schizosaccharomycetales

In this study, the lipid fractions i.e. neutral (NL), phospho-(PL) and glycolipids (GL) with associated fatty acids (FAs) of 54 strains, representing the Schizosaccharomycetales, were analyzed during stationary growth phase and compared. Trace amounts of linoleic acid (18:2) were present in most of the strains representing Schizosaccharomyces. An increased percentage 18:2 was observed in the PL fraction when compared to the NL fraction. This is possibly related to membranes requiring polyunsaturated FAs for fluidity. On the basis of the percentage oleic acid (18:1) and 18:2 FAs in the different lipid fractions, the Schizosaccharomycetales can clearly be divided into two groups i.e. Group 1 (represented by the genus Hasegawaea) comprising strains producing relatively large amounts of 18:2 and relatively low amounts of 18:1 when compared to Group 2 (represented by the genus Schizosaccharomyces comprising Schizosaccharomyces octosporus and Schizosaccharomyces pombe). These results are in accordance with 18S and 26S rRNA base sequence analyses and emphasize the difference between the genera Hasegawaea and Schizosaccharomyces. Utilizing gas chromatography-mass spectrometry analyses, it was found that these strains were all capable of producing gamma-linolenic acid. This further emphasizes the uniqueness of this order in the Dikaryomycota.     

Low pH-induced membrane fatty acid alterations in oral bacteria

Four oral bacterial strains, of which two are considered aciduric and two are considered acid-sensitive, were grown under glucose-limiting conditions in chemostats to determine whether their membrane fatty acid profiles were altered in response to environmental acidification. Streptococcus gordonii DL1, as well as the aciduric strains S. salivarius 57.I, and Lactobacillus casei 4646 increased the levels of mono-unsaturated membrane fatty acids. The non-aciduric strain S. sanguis 10904 did not alter its membrane composition in response to pH values examined here. Thus, in response to low pH, aciduric oral bacteria alter their membrane composition to contain increased levels of long-chained, mono-unsaturated fatty acids. This suggests that membrane fatty acid adaptation is a common mechanism utilized by bacteria to withstand environmental stress.     

Light,nutrients and the fatty acid composition of stream periphyton

1. While the balance of light and nutrients is known to influence the food quality of herbivores by altering algal phosphorus and nitrogen content, the combined effects of light and nutrients on fatty acid synthesis in freshwater periphyton are relatively unknown. In this study, we manipulated light and phosphorus concentration in large, flow‐through experimental streams to examine their effects on both elemental stoichiometry and fatty acid content in periphyton. 2. Two levels of phosphorus (4 and 80 μg L^?1) and three of light (17, 40, 110 μmol photons m^?2 s^?1) were applied in a factorial design in two separate experiments. Diatoms dominated periphyton communities in both experiments, comprising >95% of algal biovolume. Periphyton growth in the streams was simultaneously affected by both resources, even at low rates of supply. 3. Periphyton C/P and C/N ratios increased with light augmentation and decreased with phosphorus enrichment, and consistent with the light : nutrient hypothesis (LNH). Light effects were strongest in streams with low phosphorus concentrations. 4. Periphyton fatty acids reflected the dominance of diatoms : palmitic (16 : 0), palmitoleic (16 : 1ω7) and eicosapentanoic (20 : 5ω3) were the principal saturated (SAFA), monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA), respectively. Linoleic (18 : 2ω6) and linolenic (18 : 3ω3) acids, characteristic of chlorophytes and cyanophytes, were rare, comprising <2% of total fatty acids. 5. Periphyton fatty acid profiles were highly sensitive to light and phosphorus. The proportion of fatty acids comprised by SAFA and MUFA increased with light augmentation and decreased with phosphorus enrichment, whereas PUFA decreased with light and increased with phosphorus. Light effects on fatty acid composition were strongest in phosphorus‐poor streams. PUFA declined with increasing light/phosphorus ratios in the streams, whereas ‘energy’ fatty acids (16 : 0 and 16 : 1) increased. The ratio of SAFA/PUFA was strongly and positively correlated with C/P and C/N ratios. SAFA and MUFA, normalised to dry mass, increased two‐ to threefold with increasing light, while PUFA normalised to dry mass was not significantly affected by light. 6. Similarities in the responses of fatty acids and elemental stoichiometry to light and phosphorus treatments suggested that they were influenced by a common mechanism. Both components of food quality appeared to be sensitive to light‐regulated rates of carbon fixation which, when coupled with insufficient supplies of phosphorus, caused diatom cells to store surplus carbon in SAFA, MUFA and other carbon‐rich compounds that diluted both essential fatty acids and mineral nutrients.     

Chemotaxonomy of planktonic cyanobacteria based on non-polar and 3-hydroxy fatty acid composition

Twenty-eight axenio planktonic cyanobacterial strains (10 Microcystis, three Oscillatoria, one Spirulina, one Aphanizomenon, 13 Anabaena) were investigated for their fatty acid composition by measurement of non-polar and hydroxy fatty acids. No 2-hydroxy fatty acids were detected in any strain, but 3-hydroxy fatty acids were detected in minor quantities in 24 strains. The highest portion of total fatty acids were non-polar fatty acids. Qualitative and quantitative analyses of 3-hydroxy fatty acids showed no taxonomic value in these strains, while the type of non-polar fatty acid composition was shown to be consistent within Microcystis and Anabaena strains, distinguishing them as type 4, characterized by the presence of 18:4, and type 2, characterized by 18:3 (α) of the Kenyon-Murata system. Two Oscillatoria agardhii Gomont strains were also included in the type 2 group due to the presence of 18: 3 (α), but the difference in characteristics of 16:2 and 16:3 between O. agardhii and Anabaena further divided type 2 into two subgroups: type 2A for Anabaena and type 2B for O. agardhii. A simplified unweighted pair group method with arithmetic averages (UPGMA) dendrogram demonstrated that the classification of 28 strains (Microcystis spp., Anabaena spp., Aphanizomenon flos-aquae (Lemmermann) Ralfs f. gracile (Lemmermann) Elenkin, O. agardhii and Spirullnasubsalsa Oersted ex Gomont based on numerical analysis of non-polar fatty acids corresponded to morphological species criteria, suggesting that non-polar fatty acid composition is a valuable chemical marker in the taxonomy of planktonic cyanobacteria. However, the fatty acid composition in Oscillatoria raciborskii is similar to that of Microcystis and very different from that of O. agardhii, suggesting its special position in Oscillatoria and the chemical diversity in the genus Oscillatoria.     

Lipids in roots of Pinus sylvestris seedlings and in mycelia of Pisolithus tinctorius during ectomycorrhiza formation: changes in fatty acid and sterol composition

The composition of fatty acids and sterols in soil lipid fractions is often used as a global indicator for the status and changes of soil microbial communities. In order to validate such analyses in the context of ectomycorrhizal communities, an experiment was performed in which seedlings of Pinus sylvestris and the fungus Pisolithus tinctorius were grown separately, or combined to form ectomycorrhiza under axenic conditions. Fatty acids of the neutral lipid fraction (NLFAs) and the phospholipid fraction (PLFAs) as well as sterols were identified and quantified by gas chromatography–mass spectrometry. When grown separately, the two organisms differed strongly with respect to the sterol composition. Sterols had a much higher relative abundance in the fungus in comparison with the plant, and the two main fungal sterols, ergosterol and 24‐ethyllanosta‐8,24(24′)‐diene‐3beta,22zeta‐diol (Et lano 8,24), as well as six minor fungal sterols were not found in the plant. On the other hand, the three sterols found in plant roots were absent from the fungus. With regard to fatty acids, the lipids of both organisms contained the same three major PLFAs, namely n16:0, 18:2–9,12c, and 18:1–9c. However, plant lipids contained, in addition, eight PLFAs and five NLFAs that were not present in the fungus. On the other hand, the fungus contained two PLFAs and two NLFAs that were not present in the plant. When the fungus and the plant were brought together, there was a drastic change in the lipid composition of the root: within a day, all the saturated fatty acids in the NLFA fraction increased very strongly and then slowly decreased but remained at an elevated level throughout the experiment. All these saturated fatty acids also started to appear in the extraradical fungal mycelium; they increased steadily and reached their highest levels at the end of the experiment. These results indicate that in symbiosis, the fungus transports plant lipids from the symbiotic interface to the extraradical mycelium. Concerning sterols, the extraradical mycelium acquired only a small amount of plant‐specific sterols. However, its ergosterol content steadily decreased whereas the content of Et lano 8,24 remained high, causing the ratio of these two sterols to decrease from 1 : 7 to 1 : 20, whereas in the ectomycorrhizal root, the opposite phenomenon occurred, so that the ratio increased to a value of almost 1 : 1. The marked changes in the composition of the extraradical mycelium were well reflected in a principal component analysis of all lipid components. The present results show that a given ectomycorrhizal fungus may display markedly different lipid compositions in its intraradical and extraradical parts. In addition, they highlight a potential role of plant lipid transfer from the root to the fungus in the functioning of the ectomycorrhizal symbiosis.     

Long chain‐polyunsaturated fatty acids modulate membrane phospholipid composition and protein localization in lipid rafts of neural stem cell cultures

Rat neural stem cells/neural progenitors (NSC/NP) are generally grown in serum‐free medium. In this study, NSC/NP were supplemented with the main long‐chain polyunsaturated fatty acids (PUFAs) present in the brain, arachidonic acid (AA), or docosahexaenoic acid (DHA), and were monitored for their growth. Lipid and fatty acid contents of the cells were also determined. Under standard conditions, the cells were characterized by phospholipids displaying a highly saturated profile, and very low levels of PUFAs. When cultured in the presence of PUFAs, the cells easily incorporated them into the phospholipid fraction. We also compared the presence of three membrane proteins in the lipid raft fractions: GFR and connexin 43 contents in the rafts were increased by DHA supplementation, whereas Gβ subunit content was not significantly modified. The restoration of DHA levels in the phospholipids could profoundly affect protein localization and, consequently, their functionalities. J. Cell. Biochem. 110: 1356–1364, 2010. © 2010 Wiley‐Liss, Inc.