Chemical Synthesis and Gas Chromatographic Behaviour of γ-Stearidonic (18:4n-6) Acid

γ-Stearidonic acid, 18:4n-6, a potential product of β-oxidation of arachidonic acid (20:4n-6), was only recently positively identified in a living organism—a thermophilic cyanobacterium Tolypothrix sp., albeit at low levels, whilst some indirect evidence suggests its wider presence, e.g. in a unicellular marine alga. We have prepared 18:4n-6 using an iodolactonisation chain-shortening approach from 22:5n-6 and obtained its 1H-, 13C-, COSY- and HSQC NMR spectra, with 18:5n-3 spectra also recorded for a comparison. The GC and GC-MS behaviour of its methyl ester was also studied. Like another Δ3 polyunsaturated acid, octadecapentaenoic (18:5n-3), 18:4n-6 rapidly yields 2-trans isomer upon formation of dimethyloxazoline derivative. On a polar ionic liquid phase (SLB-IL100, 200 °C) the methyl ester could be mistaken for 18:3n-3, while on methylsilicone phase (BP1, 210 °C) it eluted ahead of 18:3n-6 and 18:4n-3, suggesting that when present it may be easily misidentified during GC analysis of fatty acids

Idiomarina gen. nov., comprising novel indigenous deep-sea bacteria from the Pacific Ocean, including descriptions of two species, Idiomarina abyssalis sp nov and Idiomarina zobellii sp nov.

Two bacterial strains, KMM 227(T) and 231(T), were isolated from seawater samples collected from the north-western Pacific Ocean at a depth of 4000-5000 m and were characterized using polyphasic taxonomy, Both were Gram-negative, psychrotolerant, heterotrophic, aerobic and required NaCl for growth (0.6-15.0%). The temperature for growth was 4-30 degrees C. Both strains were rod-shaped, with a single flagellum, However, strain KMM 231(T) revealed a single long fimbrium, Cellular fatty acids detected in the isolates were predominantly odd-numbered and iso-branched, with 15 and 17 carbons (ca. 70%), Also present were saturated and monounsaturated straight-chain fatty acids. Results of phylogenetic analyses, employing three tree-making methods, strongly indicated that the two strains formed a distinct lineage within a clade containing the genera Alteromonas, Colwellia and Pseudoalteromonas. in the gamma-Proteobacteria, The two strains shared 16S rDNA sequence similarity of 96.9% and genomic DNA relatedness of 27%; the latter was determined by dot-blot hybridization, The strains were differentiated by the presence of fimbria, production of chitinase, ability to grow on 15% NaCl and BIOLOG profiles. Given the polyphasic evidence accumulated in this study, it is proposed that the two deep-sea isolates be classified in the genus Idiomarina gen, nov., as Idiomarina abyssalis sp, nov. (type strain is KMM 227(T)) and Idiomarina zobellii sp, nov. (type strain is KMM 231(T)).