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In the microbial loop, organic matter, Irrespective of its origin and composition, is incorporated in the food chains only after it has been converted into bacterial biomass. The absence of polyunsaturated fatty acids (PUFAs) in bacteria leads to the loss of these components in the initial h k of the microbial loop. Thls results in significant differences in the nutritional value of the initial links of food webs and the microbial loop with respect to essential fatty acids. We investigated the fatty acid composition and the capability of biosynthesizing PUFAs in marine zooflagellates and ciliates that constitute links of the microbial loop. The composition of marine zooflagellate Bodo sp. varied with substrate but in all experiments flagellates contained PUFAs. Bodo sp. is capable of synthesizing PUFAs, and 22:6(n-3) synthesis rates were especially high. The ciliate Euplotes crassus was found to contain essential fatty acids. Despite the fact that synthesis rates of PUFAs in ciliates were markedly lower compared to that in zooflagellates, the occurrence of essential fatty acids in c l a t e s further enriches the biochemical composition of the microbial loop. It was shown that flagellates and ciliates are the source of PUFAs in the microbial loop. This compensates for the drawbacks of the microbial loop, connected with the specific biochemical composition of bacteria.

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Fatty acids (FA) of two species of abyssal Echinodermata-the sea star (Asteroidea) Eremicaster vicinus and the sea urchin (Echinoidea) Kamptosoma abyssale-from the Kuril-Kamchatka Trench, collected at depths of 5210 and 6183 m, were analyzed. Lipids of these deposit-feeding animals showed similar FA compositions: 20.05-16.08% saturated, 42.20-39.50% monoenoic, and 37.75-44.42% polyunsaturated FA, respectively. The contents of odd-and branched-chain FA were 17.35% and 8.80%, respectively. A significant part of FA was represented by uncommon FA such as 21:4(n-7), 22:4(n-8), 22:5(n-5), and 23:4(n-9), earlier discovered in deep-sea foraminifera. Also, the newly found acid, related to the ω2 family, Δ5,8,11,14,17,20-22:6(n-2), amounted 1.60% and 0.33% of total FA, respectively, for the two species. Such unusual FA composition of these abyssal species can be explained by the transfer and modification of FA from consumed foraminifera, which in turn, feed on bacteria.Keywords Abyssal Á Echinodermata Á PUFA new acid 22:6(n-3)Lipids (2020) 55: 291-296. AbbreviationsDMOX 4,4-dimethyloxazoline derivatives ECL equivalent chain length FA fatty acid(s) FAME fatty acid methyl esters GC gas chromatography GC-MS gas chromatography-mass spectrometry MUFA monounsaturated fatty acids NMI non-methylene-interrupted fatty acids PUFA polyunsaturated fatty acids SFA saturated fatty acids * Vasily I. Svetashev

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Pro-proliferative oncogenic signaling is one of the hallmarks of cancer. Specific targeting of such signaling pathways is one of the main approaches to modern anti-cancer drug discovery, as opposed to more traditional search for general cytotoxic agents. Natural products, especially from marine sources, represent a largely untapped source of chemical diversity, which so far have mostly been screened for cytotoxicity. Here we present a pioneering pipeline of high-throughput screening of marine-based activities targeted against the Wnt signaling pathway, which is one of the key factors in oncogenic transformation, growth and metastasis in different cancers, including the devastating triple-negative breast cancer (TNBC) currently lacking any targeted therapies. This pipeline consisted of collection and characterization of numerous invertebrates during the SokhoBio expedition to the Kuril Basin in North Pacific, preparation of extracts from these specimen, and their screening in dedicated assays monitoring Wnt signaling in TNBC cells. This approach yielded a number of promising hits, including highly specific anti-Wnt activities targeting multiple levels within the Wnt pathway from Ophiura irrorata and other Pacific brittle stars.