Fatty acid methyl ester (FAME) profiles as measures of soil microbial community structure

Analysis of fatty acid methyl ester (FAME) profiles extracted from soils is a rapid and inexpensive procedure that holds great promise in describing soil microbial community structure without traditional reliance on selective culturing, which seems to severely underestimate community diversity. Interpretation of FAME profiles from environmental samples can be difficult because many fatty acids are common to different microorganisms and many fatty acids are extracted from each soil sample. We used principal components (PCA) and cluster analyses to identify similarities and differences among soil microbial communities described using FAME profiles. We also used PCA to identify particular FAMEs that characterized soil sample clusters. Fatty acids that are found only or primarily in particular microbial taxa-marker fatty acids-were used in conjunction with these analyses. We found that the majority of 162 soil samples taken from a conventionally-tilled corn field had similar FAME profiles but that about 20% of samples seemed to have relatively low, and that about 10% had relatively high, bacterial:fungal ratios. Using semivariance analysis we identified 21:0 iso as a new marker fatty acid. Concurrent use of geostatistical and FAME analyses may be a powerful means of revealing other potential marker FAMEs. When microbial communities from the same samples were cultured on R2A agar and their FAME profiles analyzed, there were many differences between FAME profiles of soil and plated communities, indicating that profiles of FAMEs extracted from soil reveal portions of the microbial community not culturable on R2A. When subjected to PCA, however, a small number of plated communities were found to be distinct due to some of the same profile characteristics (high in 12:0 iso, 15:0 and 17:1 ante A) that identified soil community FAME profiles as distinct. Semivariance analysis indicated that spatial distributions of soil microbial populations are maintained in a portion of the microbial community that is selected on laboratory media. These similarities between whole soil and plated community FAME profiles suggest that plated communities are not solely the result of selection by the growth medium, but reflect the distribution, in situ, of the dominant, culturable soil microbial populations.     

高效薄层色谱测定湛江等鞭金藻培养过程脂质变化

【目的】研究湛江等鞭金藻(Isochrysis zhangjiangensis)由氮元素丰富至限制培养过程中脂质成分的变化。【方法】利用高效薄层色谱(HPTLC)分离分析微藻中脂质。【结果】随着培养基中营养物质的消耗,细胞逐渐处于胁迫状态,在这种状态下,细胞大量积累贮存脂质—甘油三脂(TAG),组成生物膜系统的单半乳糖甘油二脂(MGDG)、硫代异鼠李糖甘油二脂(SQDG)、磷脂酰甘油(PG)和磷脂酰胆碱(PC)含量降低,而游离脂肪酸(FFA)、甘油二脂(DAG)、双半乳糖甘油二脂(DGDG)、磷脂酰肌醇(PI)和磷脂酰乙醇胺(PE)则相对稳定。【结论】HPTLC可作为一种简便、可靠的微藻中脂质分离分析方法,为研究微藻油脂代谢途径以及甘油三脂(TAG)的调控积累提供有效手段。     

Requirement of PPARalpha in maintaining phospholipid and triacylglycerol homeostasis during energy deprivation

The peroxisome proliferator-activated receptor alpha (PPARalpha) has been implicated as a key control of fatty acid catabolism during the cellular fasting. However, little is known regarding changes of individual fatty acids in hepatic triacylglycerol (TG) and phospholipid (PL) as a result of starvation. In the present work, the effects of 72 h fasting on hepatic TG and PL fatty acid profiles in PPARalpha-null (KO) mice and their wild-type (WT) counterparts were investigated. Our results indicated that mice deficient in PPARalpha displayed hepatomegaly and hypoketonemia following 72 h starvation. Histochemical analyses revealed that severe fatty infiltration was observed in the livers of KO mice under fasted conditions. Furthermore, 72 h fasting resulted in a 2.8-fold higher accumulation of hepatic TG in KO mice than in WT mice fasted for the same length of time. Surprisingly, the total hepatic PL contents in fasted KO mice decreased by 45%, but no significant change in hepatic PL content was observed in WT mice following starvation. Gas chromatographic analysis indicated that KO mice were deprived of arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) acids during fasting. Taken together, these results show that PPARalpha plays an important role in regulation of fatty acid metabolism as well as phospholipid homeostasis during energy deprivation.     

Effects of long-term starvation on body weight and body composition of juvenile channel catfish, Ictalurus punctatus, with special emphasis on amino acid and fatty acid changes

Triplicate groups of 30 channel catfish Ictalurus punctatus (initial weight: 76.13 ± 0.78 g) were stocked in indoor flow‐through fiberglass tanks and starved for 80 days. Body weight, morphometric parameters, body composition, amino acid and fatty acid changes in muscle and liver tissues were investigated to determine the effect of long‐term starvation on body weight and body composition of juvenile channel catfish. During the starvation period, body weight, condition factor (CF), viscerosomatic index (VSI), hepatosomatic index (HSI) and intraperitoneal fat ratio (IPR) declined (P < 0.05). In the whole body, both protein and lipid decreased while changes in the amount of fat were relatively rapid. Hepatic lipid and carbohydrate contents declined as starvation progressed, but crude protein and moisture contents increased (P < 0.05). In contrast, muscle crude protein showed a greater decline than did muscle lipids, and muscle glycogen remained relatively constant. During the 80‐day starvation period the ratio of total essential amino acids (EAA) to total non‐essential amino acids (NEAA) in muscle and liver (P < 0.05) increased. In muscle tissue, total mono‐unsaturated fatty acids (MUFA) and n‐6 fatty acids decreased, but total saturated fatty acids (SFA) and n‐3 fatty acids, as well as the ratio of n‐3 to n‐6 fatty acids increased (P < 0.05). However, in the liver, starvation resulted in the relative increase of total MUFA and reduction in n‐3 fatty acid contents as well as the ratio of n‐3 to n‐6 fatty acids (P < 0.05). Based on these observations, lipids and glycogen can be considered as more important sources of catabolizable energy in liver, whereas protein might be preferentially mobilized in muscle; lipids played a more important role as energy reserves on a relative basis in the whole body. Channel catfish preferentially utilized NEAA to EAA as an energy substrate and preferentially reserved EAA during starvation. Mobilization of fatty acids showed more variation in the muscle and liver during starvation.     

Effect of glucose on the fatty acid composition of Cupriavidus necator JMP134 during 2,4-dichlorophenoxyacetic acid degradation: implications for lipid-based stable isotope probing methods

Combining lipid biomarker profiling with stable isotope probing (SIP) is a powerful technique for studying specific microbial populations responsible for the degradation of organic pollutants in various natural environments. However, the presence of other easily degradable substrates may induce significant physiological changes by altering both the rate of incorporation of the target compound into the biomass and the microbial lipid profiles. In order to test this hypothesis, Cupriavidus necator JMP134, a 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading bacterium, was incubated with [(13)C]2,4-D, [(13)C]glucose, or mixtures of both substrates alternatively labeled with (13)C. C. necator JMP134 exhibited a preferential use of 2,4-D over glucose. The isotopic analysis showed that glucose had only a small effect on the incorporation of the acetic chain of 2,4-D into the biomass (at days 2 and 3) and no effect on that of the benzenic ring. The addition of glucose did change the fatty acid methyl ester (FAME) composition. However, the overall FAME isotopic signature reflected that of the entire biomass. Compound-specific individual isotopic analyses of FAME composition showed that the (13)C-enriched FAME profiles were slightly or not affected when tracing the 2,4-D acetic chain or 2,4-D benzenic ring, respectively. This batch study is a necessary step for validating the use of lipid-based SIP methods in complex environments.     

高、低氮浓度对2株真眼点藻的生长和油脂积累的影响

【目的】研究氮浓度对真眼点藻纲(Eustigmatophyceae)的2株高产油微藻大真眼点藻(Eustigmatos magnus,EM)和波氏真眼点藻(Eustigmatos polyphem,EP)的细胞形态、生长、总脂含量、脂质组成和脂肪酸组成与含量的时序变化规律。【方法】利用高氮(18.0 mmol/L NO3?-N)和低氮(3.6 mmol/L NO3?-N)浓度培养微藻。【结果】形态观察结果表明,大真眼点藻(E. magnus)和波氏真眼点藻(E. polyphem)营养细胞具有1个周生的裂叶状叶绿体,细胞质中有液泡,内含能够振动的颗粒物,以及一个较为明显的红色色素体;生殖方式通过形成2个D形或4个四角形的似亲孢子;随着培养周期的延伸和营养盐的消耗,细胞中油体逐步形成,其数量不断增加,体积不断增大。实验结果表明,初始氮浓度对2种微藻的总脂积累及生长均有显著影响(P<0.05),低氮浓度下2种微藻的生物质浓度分别为9.0 g/L和8.5 g/L,均低于高氮浓度下的生物质浓度。而低氮浓度下2种微藻的总脂、中性脂和总脂肪酸的含量以及总脂、中性脂与总脂肪酸的单位体积产率均明显高于高氮浓度组,其最高值分别为：59.10%、51.90%、46.95%和0.28、0.24、0.22 g/(L·d) (EM);64.20%、56.80%、50.01%和0.32、0.28、0.25 g/(L·d) (EP)。脂肪酸分析结果表明,两种微藻的脂肪酸主要成分均为棕榈酸(C16:0)、棕榈油酸(C16:1)、油酸(C18:1)和二十碳五烯酸(C20:5,EPA),四者的总含量(占总脂肪酸)分别达到85.83%和85.48%,其中棕榈油酸的含量最高。【结论】低氮浓度胁迫有利于大真眼点藻和波氏真眼点藻细胞内油脂的积累,两种微藻均为适合于生产生物柴油的油脂生产藻株。     

Western diamondback rattlesnakes demonstrate physiological and biochemical strategies for tolerating prolonged starvation

Because of the uncertainty in food resources in nature, all animals face the possibility of imposed periods of fasting (i.e., starvation) at some point in their lives. I investigated physiological and biochemical responses to starvation that occur in a species of rattlesnake known to tolerate successfully prolonged periods of starvation in the wild. Sixteen subadult Crotalus atrox were fasted for up to 24 wk under controlled conditions simulating their active season. Snakes exhibited significant reductions in plasma glucose but increased circulating ketone bodies. Fasting snakes lost mass at a linear rate and increased their relative moisture content during the experiment. The bodies of fasting snakes demonstrated an increase in their fatty acid (FA) unsaturation index and were apparently able to "spare" essential FAs effectively from beta -oxidation. Endogenous essential and nonessential amino acids were used indiscriminately to fuel energetic requirements, suggesting that essential amino acids are not preferentially spared during starvation. The (15)N signature of excreted nitrogenous waste increased significantly, presumably as a result of shifting amino acid source pools during starvation. Because our comparative knowledge of starvation physiology contains large taxonomic gaps, particularly with respect to amphibians and reptiles, an understanding of the biological responses exhibited by these animals may offer insight into the evolution of physiological strategies animals employ to cope with the pressures of starvation.     

Fat pad triacylglycerol fatty acid loss and oxidation as indices of total body triacylglycerol fatty acid mobilization and oxidation in starving mice

We tested our hypothesis that, kinetically, triacylglycerol fatty acids in heterogeneously labeled adipocytes behave similarly to the whole fat pad triacylglycerol fatty acid during starvation in mice. Adipose triacylglycerol fatty acids were labeled with [1-14C]palmitate (complexed to albumin) by injection of a small bolus (2-5 microliter) into either epididymal or inguinal fat pads. Both 14C-labeled triacylglycerol fatty acid spec. act. and breath 14CO2 spec. act. were monitored 30 min after tracer injection and after 24-72 h starvation. Adipose triacylglycerol fatty acid spec. act. remained approximately constant during fasting, i.e., tracer and mass disappeared at similar rates. Negligible translocation of labeled triacylglycerol fatty acid from the injection site to other parts of the same fat pad or to distant fat pads occurred. Triacylglycerol fatty acid was mobilized more slowly from epididymal than from inguinal fat pads in two of three studies. Triacylglycerol fatty acid disappearance (loss) from inguinal fat pads was more replicable than from epididymal fat pads and more closely reflected the fall in whole body total lipid during starvation. The estimated percent of breath CO2-carbon derived from adipose triacylglycerol fatty acid increased from an average of approx. 32% in the postabsorptive state to about 77% after 48 h starvation. The data help to validate the direct tracer injection technique as a means of studying adipose triacylglycerol fatty acid turnover and oxidation. This approach should be particularly useful for studying the fate of adipose triacylglycerol fatty acid when it is mobilized. e.g., during states of inanition and starvation and in response to hormones and cancer-induced cachexia.     

Subgrouping of bacterial populations by cellular fatty acid composition

Abstract The cellular fatty acid composition of six bacterial species isolated from the seeds and leaves of sugar beet ( Beta vulgaris ) and from soil were analysed. The quantitative data from the fatty acid methyl ester (FAME) profiles were highly reproducible. Numerical analysis of Xanthomonas maltophilia . FAME profiles sub-grouped strains according to when they were isolated in the growing season. The analytical method used was sensitive enough to differentiate strains of Klebsiella terrigena isolated from either soil or leaves. The results from this study confirm reports that analyses of bacterial FAME composition were rapid to perform, specific and allowed differentiation of strains within the same species.     

Effects of freezing and drying grass products prior to fatty acid extraction on grass fatty acid and lipid class composition--a technical note

Grass and grass silage represent a rich and natural source of omega-3 polyunsaturated fatty acids, in particular linolenic acid, for ruminants. Recent research, focusing on improving the content of these beneficial fatty acids in grass, requires storage of the forage samples prior to analysis. In this study, we evaluated whether conservation of fresh grass and grass silage by freezing (1 and 4 weeks,--18 degrees C) and/or drying (24h, 50 degrees C) affected its fatty acid content and induced shifts between lipid classes. FA were extracted using chloroform/methanol (2/1, v/v) and triacylglycerols (TAG), free fatty acids (FFA) and polar lipids (PL) were separated by thin layer chromatography. Fatty methyl esters (FAME) were identified by gas chromatography. Loss of thawing liquor might provoke a dramatic decrease in extractable lipid after frozen storage of both grass and grass silage. Morever, after frozen storage, fatty acids in grass but not in grass silage seem subjected to a higher rate o f lipolysis and oxidation, as suggested by increased quantities of FFA (3.1, 7.6, 8.4 % of total FAME) and reduced proportions of poly-unsaturated fatty acids (79.5, 73.6 and 74.1 % of total FAME) when analysing fresh grass samples directly or after 1 and 4 weeks of frozen storage, respectively. Drying of fresh grass did not provoke changes in FA composition, but distribution of FA over lipid classes was significantly altered, with an increase in TAG (5.1 to 17.9 % of total FAME) and FFA (2.4 to 14.9 % of total FAME) and lower proportions of PL (90.7 to 55.7 % of total FAME).     

Biochemical and Molecular Characterization of Some Centaurea Species Growing in the Eastern Anatolia Region of Turkey

Random amplified polymorphic DNA (RAPD) and fatty acid (FAME) profiles were used to examine phenotypic and genetic relationships among 16 Centaurea species growing wild in the eastern Anatolia region of Turkey. Thirteen decamer primers were used to examine polymorphism. According to the RAPD results, 99 amplicons in the size range of 50–1000 bp were produced from 13 primers in 16 Centaurea species. Genetically four distinct groups were determined among the species of Centaurea, which represents high genetic variation. In the 16 species, 14 fatty acids were determined according to FAME results. Both FAME and RAPD results showed that C. virgata is genetically different from other species. The differences in the composition of fatty acids among Centaurea species suggest that fatty acid profiles could be used to differentiate among some of these species. Results of this study show that RAPD and FAME analyses are consistent.     

Influence of starvation on the lung: effect on glucose and palmitate utilization.

The relative utilization of [U-14C]glucose and [1-14C]palmitate was examined in lung slices of male Long Evans hooded rats fed ad libitum and starved for 72 h. Food deprivation (72-h fast) significantly decreased [U-14C]flucose oxidation and incorporation into lung lipids. Glucose incorporation into phospholipid-fatty acid (53%) was, in proportion, more markedly reduced than into phospholipid-gluceride glycerol (33%), suggesting that glucose was being conserved for the formation of alpha-glycerol phosphate. (1-14C) palmitate utilization following fasting showed a significant 40% increase in oxidation, and a significant 16% increase in phospholipids, indicating preferential utilization of fatty acids over glucose. Phospholipid fatty acid composition, surface tension measurements and volume-pressure curves were not affected by fasting. Khe data indicate that glucose and palmitate metabolism are interrelated, and that the relative utilization of these substrates is changed to maintain essential lung lipids during an altered physiologic state.     

Polyphasic taxonomy of symbiotic rhizobia from wild leguminous plants growing in Egypt

About 20 strains of rhizobia from wild legumes were characterized based on numerical analysis of phenotypic characteristics, nodulating ability, fatty acid methyl esters (FAME) and SDS-PAGE profiles of whole cell proteins. FAME analysis revealed that palmitic (16:0), stearic (18:0) and arachidonic (20:0) were detected in most of wild-legume rhizobia, the latter being uncommon in fatty acid profiles of Rhizobium and Sinorhizobium. Numerical analysis of FAME classified strains of wild-legume rhizobia into 9 clusters and one heterogeneous group. There was both agreement and disagreement with the clustering data based on phenotypic analysis and FAME analysis. Four strains were grouped together in the same cluster based on both methods. However, 4 another strains, which were placed in one cluster of phenotypic analysis, were distributed in several clusters after FAME analysis. SDS-PAGE of whole-cell proteins revealed that the rhizobial strains exhibited protein profiles with peptide bands ranging from 5-19 band per profile and showed molar mass of 110-183 kDa. As in the case of FAME analysis, numerical analysis of protein bands was compared with clustering of phenotypic analysis. Agreement of the two methods was obvious when clustering some strains but conflicted in the classification of some other strains. However, integration of the three methods could be the basis of a polyphasic taxonomy. The twenty strains of wild-legume rhizobia were finally classified as follows: 12 strains related to Rhizobium leguminosarum, 5 strains related to Sinorhizobium meliloti and 3 strains to Rhizobium spp. Rhizobia nodulating wild herb legumes are among indigenous strains nodulating crop legumes in cultivated as well as noncultivated lands.     

Culture age and carbamoylcholine increase the incorporation of endogenously synthesized linoleic acid in lipids of Trypanosoma cruzi epimastigotes

Physiological and cellular adaptations to environmental changes are known to be related to modifications in membrane lipids. This work provides metabolic and compositional evidence that Trypanosoma cruzi epimastigotes are able to synthesize and desaturate fatty acids, to incorporate them into their lipids, and to modify this incorporation when carbamoylcholine is present in the medium. The fatty acids formed from [2-(14)C]acetate in the period from 2 to 9 days were mostly (70%) incorporated in phospholipids, the remainder 30% being recovered in neutral lipids, such as triacylglycerols (TAG) and diacylglycerols (DAG). The main fatty acids formed from [2-(14)C]acetate were saturates (16:0, 18:0), monoenes (16:1, 18:1) and dienes (mostly 18:2). The ratios between labelled unsaturated and saturated fatty acids increased continuously with growth, consistent with a precursor-product relationship between the main fatty acids, and with the occurrence in T. cruzi of Delta(9)- and Delta(12)-desaturases. From days 2 to 5, [(14)C]18:2 was the main fatty acid produced. Accordingly, the fatty acid profiles showed a significant increase in the percentage of 18:2 in all lipids in the period under study, especially in the first 2 to 5 days. In the presence of carbamoylcholine, the labelling of DAG and TAG with [(14)C]18:2 augmented. The results indicate that T cruzi is able to synthesize the main types of fatty acids required to form its membrane lipids, and to exchange them actively in response to environmental stimuli.     

Unique Honey Bee (Apis mellifera) Hive Component-Based Communities as Detected by a Hybrid of Phospholipid Fatty-Acid and Fatty-Acid Methyl Ester Analyses

Microbial communities (microbiomes) are associated with almost all metazoans, including the honey bee Apis mellifera. Honey bees are social insects, maintaining complex hive systems composed of a variety of integral components including bees, comb, propolis, honey, and stored pollen. Given that the different components within hives can be physically separated and are nutritionally variable, we hypothesize that unique microbial communities may occur within the different microenvironments of honey bee colonies. To explore this hypothesis and to provide further insights into the microbiome of honey bees, we use a hybrid of fatty acid methyl ester (FAME) and phospholipid-derived fatty acid (PLFA) analysis to produce broad, lipid-based microbial community profiles of stored pollen, adults, pupae, honey, empty comb, and propolis for 11 honey bee hives. Averaging component lipid profiles by hive, we show that, in decreasing order, lipid markers representing fungi, Gram-negative bacteria, and Gram-positive bacteria have the highest relative abundances within honey bee colonies. Our lipid profiles reveal the presence of viable microbial communities in each of the six hive components sampled, with overall microbial community richness varying from lowest to highest in honey, comb, pupae, pollen, adults and propolis, respectively. Finally, microbial community lipid profiles were more similar when compared by component than by hive, location, or sampling year. Specifically, we found that individual hive components typically exhibited several dominant lipids and that these dominant lipids differ between components. Principal component and two-way clustering analyses both support significant grouping of lipids by hive component. Our findings indicate that in addition to the microbial communities present in individual workers, honey bee hives have resident microbial communities associated with different colony components.     

Fatty Acid Methyl Ester Profiles for Characterization of Glomalean Fungi and Their Endomycorrhizae

Arbuscule-forming fungi in the order Glomales form obligate endomycorrhizal associations with plants that make them difficult to quantify, and taxonomy of the group is only beginning to be objectively understood. Fatty acid methyl ester (FAME) profiles were analyzed to assess the diversity and quantity of fatty acids in 53 isolates of 24 glomalean species. Spores and endomycorrhizal roots of sudan grass (Sorghum sudanense) and the citrus rootstock Carrizo citrange (Poncirus trifoliata x Citrus sinensis) were examined. Spores yielded reproducible FAME profiles from replicate spore collections extracted from soil pot cultures despite being grown in association with a host plant and with contaminating microorganisms present. Unweighted pair group analysis revealed relatively tight clusters of groups at the intraspecific, specific, and generic levels; however, lipid profiles at the family level were convergent. Thus, FAME profile comparisons provided a robust measure of similarity below the family level. FAME profiles in sudan grass roots containing vesicles and/or spores of Glomus intraradices were more similar to spore profiles than to profiles from nonmycorrhizal roots. The FAME profiles for Gigaspora species, which do not form vesicles or spores in roots, were less distinct from nonmycorrhizal roots. G. intraradices and G. rosea produced fatty acids in roots that were distinguishable from each other as well as from the host root. Production in citrus roots of the fatty acid 16:1(inf(omega)5) cis by two Glomus species was correlated with the development of mycorrhizal colonization as measured by clearing and staining procedures and by estimates of total incidence and vesicle intensity. FAME analysis of roots not only provided a measure of colonization development but also served as an index of carbon allocated to intraradical fungal growth and lipid storage.     

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.     

Chemotaxonomic characterization of rice seedling blight complex using fatty acid methyl ester (FAME) profiles

Rice seedling blight is an important disease caused by a complex of fungi that include Fusarium, Rhizopus, Pythium, and Trichoderma species. A modified MIDI method was used for extraction of fatty acids from these causal pathogens, and fatty acid methyl ester (FAME) profiles were characterized. Factors that might affect fatty acid production, such as period of culture and saponification in extraction, were also evaluated. A total of 14 fatty acids were detected, and FAME profiles showed quantitative and qualitative variations by discriminant analysis and principal component analysis. Genus-specific FAME profiles consisting of the types of fatty acid produced and remarkable components of individual fatty acids were observed. The possibility of application as chemotaxonomic methods based on the FAME profiles for diagnosis of the rice seedling blight complex is also discussed.     

Monoenoic fatty acid requirement in V79 cells

When lipids were removed from the culture medium, growth of V79 cells ceased. Supplementation with cis-octadecenoic acids satisfied the requirement for lipids by V79 cells. After starvation of the exogenous lipids by the shift-down of the medium to lipid-free medium, the content of octadecenoic acid in phospholipids increased more slowly in V79 cells than in V79-R cells, which can grow in the lipid-starved medium. The incorporation of [14C]acetic acid into monoenoic fatty acids and phospholipid molecular species containing monoenoic fatty acids in V79 cells was lower than that in V79-R cells. The reduced formation of monoenoic fatty acids was shown to be due to deficiency in the stimulation of activity of stearoyl-CoA desaturase which is a key enzyme to convert saturated fatty acids to monoenoic fatty acids.     

Comparative lipidomic studies of Scenedesmus sp. (Chlorophyceae) and Cylindrotheca closterium (Bacillariophyceae) reveal their differences in lipid production under nitrogen starvation

Microalgae are a promising resource for the highly sustainable production of various biomaterials (food and feed), high‐value biochemicals, or biofuels. However, factors influencing the valued lipid production from oleaginous algae require a more detailed investigation. This study elucidates the variations in lipid metabolites between a marine diatom (Cylindrotheca closterium) and a freshwater green alga (Scenedesmus sp.) under nitrogen starvation at the molecular species level, with emphasis on triacylglycerols using liquid chromatography–electrospray ionization mass spectrometry techniques. A comprehensive analysis was carried out by comparing the changes in total lipids, growth kinetics, fatty acid compositions, and glycerolipid profiles at the molecular species level at different time points of nitrogen starvation. A total of 60 and 72 triacylglycerol molecular species, along with numerous other polar lipids, were identified in Scenedesmus sp. and C. closterium, respectively, providing the most abundant triacylglycerol profiles for these two species. During nitrogen starvation, more triacylglycerol of Scenedesmus sp. was synthesized via the “eukaryotic pathway” in the endoplasmic reticulum, whereas the increase in triacylglycerol in C. closterium was mainly a result of the “prokaryotic pathway” in the chloroplasts after 96 h of nitrogen starvation. The distinct responses of lipid synthesis to nitrogen starvation exhibited by the two species indicate different strategies of lipid accumulation, notably triacylglycerols, in green algae and diatoms. Scenedesmus sp. and Cylindrotheca closterium could serve as excellent candidates for the mass production of biofuels or polyunsaturated fatty acids for nutraceutical purposes.