Algal lipids are important molecules to store energy in algae and transfer energy in the marine food chain, and are potential materials for high value nutraceuticals (e.g., omega‐3 fatty acids) or biofuel production. However, how lipid biosynthesis is regulated is not well understood in many species including Eutreptiella from the phylum of Euglenozoa. Here, we characterized the fatty acid (FA) profile of an Eutreptiella species isolated from Long Island Sound, USA, using gas chromatography–tandem mass spectrometry (GC/MS/MS) and investigated their biosynthesis pathways by transcriptome sequencing. We discovered 24 types of FAs including a relatively high proportion of long‐chain unsaturated FAs. The abundances of C16, C18, and saturated FAs decreased when phosphate in the culture medium was depleted. Among the 24 FAs, docosahexaenoic acid (C22:6^{∆4,7,10,13,16,19}) was most abundant, suggesting that Eutreptiella sp. preferentially invests in the synthesis of long‐chain polyunsaturated fatty acids (LC‐PFAs). Further transcriptomic analysis revealed that Eutreptiella sp. likely synthesizes LC‐PFAs via ∆8 pathway and uses type I and II fatty acid synthases. Using RT–qPCR, we found that some of the lipid synthesis genes, such as β‐ketoacyl‐ACP reductase, fatty acid desaturase, acetyl‐CoA carboxylase, acyl carrier protein, ∆8 desaturase, and Acyl‐ACP thioesterase, were more actively expressed during light period, and two carbon fixation genes were up‐regulated in the high‐lipid illuminated cultures, suggesting a linkage between photosynthesis and lipid production. The lipid profile renders Eutreptiella sp. a nutritional prey and valuable source for nutraceuticals, and the biosynthesis pathway documented here will be useful for future research and applications.

中文翻译：

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Eutreptiella sp。中长链多不饱和脂肪酸的大量合成。（Euglenozoa）通过色谱和转录组分析发现

藻类脂质是在藻类中存储能量并在海洋食物链中转移能量的重要分子，并且是高价值保健食品（例如，ω-3脂肪酸）或生物燃料生产的潜在材料。但是，如何调节脂质的生物合成在许多物种中都未得到很好的理解，其中包括来自裸藻门的Eutreptiella。在这里，我们表征了大肠杆菌的脂肪酸（FA）谱使用气相色谱-串联质谱法（GC / MS / MS）从美国长岛湾分离出的一些物种，并通过转录组测序研究了它们的生物合成途径。我们发现了24种类型的FA，包括相对较高比例的长链不饱和FA。当培养基中的磷酸盐耗尽时，C16，C18和饱和FA的丰度降低。在24个FA中，二十二碳六烯酸（C22：6 ^{∆4,7,10,13,16,19}）含量最高，表明Eutreptiella sp.。优先投资于长链多不饱和脂肪酸（LC-PFA）的合成。进一步的转录组分析表明，大肠埃希菌sp。可能通过∆8途径合成LC-PFAs，并使用I和II型脂肪酸合成酶。使用RT-qPCR，我们发现一些脂质合成基因，例如β-酮酰基-ACP还原酶，脂肪酸去饱和酶，乙酰辅酶A羧化酶，酰基载体蛋白，Δ8去饱和酶和酰基-ACP硫酯酶，活性更高。在光照高的培养物中，两个碳固定基因被上调，这表明光合作用和脂质生产之间存在联系。脂质谱使Eutreptiella sp.。营养猎物和营养保健品的宝贵来源，此处记载的生物合成途径将对未来的研究和应用有用。