Aurélie Couzinet-Mossion

Response of CO 2 -starved diatom Phaeodactylum tricornutum to light intensity transition

In this study, we investigated the responses of Phaeodactylum tricornutum cells acclimated to 300 µmol m−2 s−1 photon flux density to an increase (1000 µmol m−2 s−1) or decrease (30 µmol m−2 s−1) in photon flux densities. The light shift occurred abruptly after 5 days of growth and the acclimation to new conditions was followed during the next 6 days at the physiological and molecular levels. The molecular data reflect a rearrangement of carbon metabolism towards the production of phosphoenolpyruvic acid (PEP) and/or pyruvate. These intermediates were used differently by the cell as a function of the photon flux density: under low light, photosynthesis was depressed while respiration was increased. Under high light, lipids and proteins accumulated. Of great interest, under high light, the genes coding for the synthesis of aromatic amino acids and phenolic compounds were upregulated suggesting that the shikimate pathway was activated. This article is part of the themed issue ‘The peculiar carbon metabolism in diatoms’.

Multiple Beneficial Lipids Including Lecithin Detected in the Edible Invasive Mollusk Crepidula fornicata from the French Northeastern Atlantic Coast

The invasive mollusk Crepidula fornicata, occurring in large amounts in bays along the French Northeastern Atlantic coasts, may have huge environmental effects in highly productive ecosystems where shellfish are exploited. The present study aims at determining the potential economic value of this marine species in terms of exploitable substances with high added value. Lipid content and phospholipid (PL) composition of this mollusk collected on the Bourgneuf Bay were studied through four seasons. Winter specimens contained the highest lipid levels (5.3% dry weight), including 69% of PLs. Phosphatidylcholine (PC) was the major PL class all year, accounting for 63.9% to 88.9% of total PLs. Consequently, the winter specimens were then investigated for PL fatty acids (FAs), and free sterols. Dimethylacetals (DMAs) were present (10.7% of PL FA + DMA mixture) revealing the occurrence of plasmalogens. More than forty FAs were identified, including 20:5n-3 (9.4%) and 22:6n-3 (7.3%) acids. Fourteen free sterols were present, including cholesterol at 31.3% of the sterol mixture and about 40% of phytosterols. These data on lipids of C. fornicata demonstrate their positive attributes for human nutrition and health. The PL mixture, rich in PC and polyunsaturated FAs, offers an interesting alternative source of high value-added marine lecithin.

Exploitable Lipids and Fatty Acids in the Invasive Oyster Crassostrea gigas on the French Atlantic Coast

Economic exploitation is one means to offset the cost of controlling invasive species, such as the introduced Pacific oyster (Crassostrea gigas Thunberg) on the French Atlantic coast. Total lipid and phospholipid (PL) fatty acids (FAs) and sterols were examined in an invasive population of C. gigas in Bourgneuf Bay, France, over four successive seasons, with a view to identify possible sources of exploitable substances. The total lipid level (% dry weight) varied from 7.1% (winter) to 8.6% (spring). Of this, PLs accounted for 28.1% (spring) to 50.4% (winter). Phosphatidylcholine was the dominant PL throughout the year (up to 74% of total PLs in winter). Plasmalogens were identified throughout the year as a series of eleven dimethylacetals (DMAs) with chain lengths between C16 and C20 (up to 14.5% of PL FAs + DMAs in winter). Thirty-seven FAs were identified in the PL FAs. Eicosapentaenoic acid (20:5n-3 EPA/7.53% to 14.5%) and docosahexaenoic acid (22:6n-3 DHA/5.51% to 9.5%) were the dominant polyunsaturated FAs in all seasons. Two non-methylene-interrupted dienoic (NMID) FAs were identified in all seasons: 7,13-docosadienoic and 7,15-docosadienoic acids, the latter being present at relatively high levels (up to 9.6% in winter). Twenty free sterols were identified, including cholesterol at 29.9% of the sterol mixture and about 33% of phytosterols. C. gigas tissues thus contained exploitable lipids for health benefits or as a potential source of high-quality commercial lecithin.

The Marine-Derived Fungus Clonostachys rosea, Source of a Rare Conjugated 4-Me-6E,8E-hexadecadienoic Acid Reducing Viability of MCF-7 Breast Cancer Cells and Gene Expression of Lipogenic Enzymes.

A marine-derived strain of Clonostachys rosea isolated from sediments of the river Loire estuary (France) was investigated for its high lipid production. The fungal strain was grown on six different culture media to explore lipid production changes. An original branched conjugated fatty acid, mainly present in triglycerides and mostly produced when grown on DCA (23% of total fatty acid composition). It was identified as 4-Me-6E,8E-hexadecadienoic on the basis of spectroscopic analyses. This fatty acid reduced viability of MCF-7 breast cancer cells in a dose dependent manner (up to 63%) at physiological free fatty acid human plasma concentration (100 μM). Reduction of gene expression of two lipogenic enzymes, the acetyl CoA carboxylase (ACC) and the fatty acid synthase (FAS) was evaluated to explore the mechanisms of action of 4-Me-6E,8E-16:2 acid. At 50 μM, 50% and 35% of mRNA gene expression inhibition were observed for ACC and FAS, respectively.

Lipids, Fatty Acids, Glycolipids, and Phospholipids

Abstract Mean total lipid (TL) content for seaweeds is 3%. It seems that TL content varies mainly depending on environmental factors (depth, water temperature, salinity, etc.). The red and brown seaweeds contain high C20/C18 polyunsaturated fatty acid ratio and high C18:1, and two major fatty acids: arachidonic acid and eicosapentaenoic acid. The green seaweeds are characterized by high C18/C20 polyunsaturated fatty acid ratio. In addition, certain species of Rhodophyceae contain atypical acids whose real origin is not always well defined (bacterial biofilm, epiphytes, etc.). Phospholipids and betaine lipids seem to be characteristic from a taxonomic point of view. In fact, brown algae orders could be classified into three groups depending on the detection of phosphatidylcholine (PC) and diacylglycerylhydroxymethyltrimethyl-β-alanine. For the green algae, PC and diacylglycerylhydroxymethyltrimethyl-β-homoserine seem most representative. Among the three phyla, Ochrophyta, followed by Rhodophyta and Chlorophyta, appears as the main source of bioactive glycolipids associated with antibacterial, antiproliferative, and antiviral activities.

Lipids From Microalgae

Abstract In this chapter, we propose to describe the major cellular lipids and their fatty acids in microalgae. This development will concern both prokaryotes (cyanophytes) and eukaryotes (diatoms, chlorophytes, cryptophytes, rhodophytes, …). The different types of lipids (particularly fatty acids) will be listed, but also the sterols, glycolipids, and phospholipids knowing that the accumulation of lipids depends on the microalgal species, growth, and environmental conditions. The neutral lipids or nonpolar lipids other than triacylglycerides, such as sterols and free fatty acids, are present at lower levels but these lipids are of great interest for the valorization of microalgae in aquaculture, nutrition, or biofuel production. Polar lipids, such as glycolipids or betaine lipids (BL) will be studied more specifically. Moreover, BL and some unusual lipids may be characteristic of a particular genus or species. BL represent a widespread class of functional and structural lipids that have been slowly studied and recognized. During stress conditions such as phosphorus deprivation, these lipids can completely replace the phospholipids in their metabolic role. Then, we will focus on the specific role played by the subcellular fractions of lipids involved in the constitution of diatoms and especially the role played by the plastids and the endoplasmic reticulum compartments in which polyunsaturated fatty acids and polar lipids are specifically synthesized.