Twelve species of marine unicellular algae have been cultured under comparable conditions and the total fatty acids determined b1' gas liquid chromatography. Some specific fatty acid relationships paralleling taxonornic groupings were detected but generally individual fatty acids within various algal classes shorved large relative variations. The four Bacillariophyceae examined were notable for fatty acid cornpositions giving iodine values (150, rvhereas in eight other classes the iodine values were all approximately 200. It is suggested that 5,8,11,14,17-eicosapentaenoic acid, found to be a common algal longer-chain polyunsaturated fatty acid, is characteristically deposited in the lipids of filter-feeders ingesting unicellular algae.
Dimethyl-β-propiothetin has been reported from several species of freshwater and marine multicellular algae. Cultures of 14 species of unicellular marine algae were treated with cold aqueous alkali. Dimethyl sulphide was liberated from Syracosphaera carterae, Skeletonema costatum, Amphidinium carteri, Phaeodactylum tricornutum, Tetraselmis sp. and Cyclotella cryptica, and is assumed to arise from dimethyl-β-propiothetin. The amounts of alkali-labile material varied, on a wet weight basis, from 0.07 to 2.9% (as thetin salt) in different organisms. The presence of the thetin in S. carterae was confirmed by other means. The thetin, and particularly its degradation products, acrylic acid and dimethyl sulphide, may influence actual fishing operations and also affect the quality of fishery products. The metabolic and ecological significance of these materials are reviewed and discussed.
The photosynthetic fixation of14CO2was studied in 10 species of chlorophycean algae and in 9 isolates of prasinophycean algae of the genus Tetraselmis.Green seaweeds had photosynthetic rates of 2.2 to 4.4 mg CO2 × h−1 × g−1, accumulated starch, glucose, fructose, and sucrose, and excreted very little recent photosynthate.Dunaliella spp. were distinguished by a high level of organic excretion (to 29.2% of the14C fixed in 2 hours), the production of glycerol and hydrogen sulfide, and the absence of dimethyl-β-propiothetin.Tetraselmis spp. excreted relatively small amounts of photosynthate in 2 hours, and produced mannitol and dimethyl-β-propiothetin but not hydrogen sulfide.
Dimethyl -8-propiothetin (DMPT) has been reported to be present in some species of unicellular phytoplankton on the basis of the evolution of dimethyl sulfide (DMS), lane of its breakdown products. The presence of BMPT In Syacosphm~cz ca16erae has now been confirmed by recipitation of it as the reineckate, with recovery and chmmatographic a n a b e s by paper and thinlayer techniques. Multicellular Uiwa Jwtzeca, which is known to contain BMPT, was used as a control. All steps were monitored by the gas-liquid chromatographic prmduse for measuring BMS. Chromat rams were run in four solvent systems. All parts of the chromatograms wereelutz, and tested for DMS. The only portion of any chromatogram that yielded B M S was that area corresponding to the Rp value of authentic DMPT.
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