On the basis of data from phenotypic and genotypic characterization and analysis of 16S rRNA gene sequences, two novel species belonging to the genus Sulfitobacter are described. Strains KMM 3584^T, a pale-yellowish, non-motile strain isolated from a starfish (Stellaster equestris), and KMM 3554^T, which is motile by means of a single subpolar flagellum and was isolated from sea grass (Zostera marina), are marine, Gram-negative, aerobic, rod-shaped organisms. Both strains have the ability to degrade gelatin, but not casein, chitin, agar, DNA, Tween 80 or starch. Strain KMM 3584^T decomposed alginate and grew at NaCl concentrations of 1–8 % and temperatures of 12–37°C, whereas strain KMM 3554^T grew in 1–12% NaCl and at temperatures of 10–30°C. The predominant fatty acid was 18:1ω7, amounting to up to 80% of the total fatty acids. The other characteristic feature was the presence of 18:2 isomers. The DNA G+C contents of KMM 3584^T and KMM 3554^T were respectively 60·0 and 63·7 mol%. The level of DNA similarity between the two strains was 33%. DNA from KMM 3584^T and KMM 3554^T had hybridization values of 5–24% and 10–41%, respectively, with DNA from the type strains of Sulfitobacter pontiacus, Sulfitobacter brevis, Sulfitobacter mediterraneus and Staleya guttiformis. It is proposed that strains KMM 3584^T (=LMG 20554^T=ATCC BAA-321^T) and KMM 3554^T (=LMG 20555^T=ATCC BAA-320^T) represent two novel species, Sulfitobacter delicatus sp. nov. and Sulfitobacter dubius sp. nov., respectively.

The n-3 and n-6 polyunsaturated fatty acid (PUFA) families are essential for important physiological processes. Their major source are marine ecosystems. The fatty acids (FAs) from phytoplankton, which are the primary producer of organic matter and PUFAs, are transferred into consumers via food webs. Mollusk FAs have attracted the attention of researchers that has been driven by their critical roles in aquatic ecology and their importance as sources of essential PUFAs. The main objective of this review is to focus on the most important factors and causes determining the biodiversity of the mollusk FAs, with an emphasis on the key relationship of these FAs with the food spectrum and trophic preference. The marker FAs of trophic sources are also of particular interest. The discovery of new symbioses involving invertebrates and bacteria, which are responsible for nutrition of the host, deserves special attention. The present paper also highlights recent research into the molecular and biochemical mechanisms of PUFA biosynthesis in marine mollusks. The biosynthetic capacities of marine mollusks require a well-grounded evaluation.