Membrane vectorial lipidomic features of coral host cells' plasma membrane and lipid profiles of their endosymbionts Cladocopium.

The symbiotic relationships between coral animal host and autotrophic dinoflagellates are based on the mutual exchange and tight control of nutritional inputs supporting successful growth. The corals Sinularia heterospiculata and Acropora aspera were cultivated using a flow-through circulation system supplying seawater during cold and warm seasons of the year, then sorted into host cells and symbionts and subjected to phylogenetic, morphological, and advanced lipid analyses. Here we show, that the lipidomes of the dinoflagellates Cladocopium C1/C3 and acroporide-specific Cladocopium hosted by the corals, are determined by lipidomic features of different thermosensitivity and unique betaine- and phospholipid molecular species. Phosphatidylserines and ceramiaminoethylphosphonates are not detected in the symbionts and predominantly localized on the inner leaflet of the S. heterospiculata host plasma membrane. The transmembrane distribution of phosphatidylethanolamines of S. heterospiculata host changes during different seasons of the year, possibly contributing to mutualistic nutritional exchange across this membrane complex to provide the host with a secure adaptive mechanism and ecological benefits.

A massive bloom of Karenia species (Dinophyceae) off the Kamchatka coast, Russia, in the fall of 2020.

In the fall of 2020, a long-lasting and massive harmful algal bloom (HAB) with extensive fields of yellow sea foam was observed in relatively cold waters (7-13 °C) off the coasts of the Kamchatka Peninsula, Russia. According to the estimates based on bio-optical parameters in satellite imagery, the Kamchatka bloom 2020 lasted for two months and covered a vast area of more than 300 × 100 km. An abundance of dead fish and invertebrates, including sea urchins, sea anemones, chitons, cephalopods, bivalves were found on shore during the bloom. Animals suffered almost 100% mortality within a depth range between 5 and 20 m. To identify the causative microalgal species, light and scanning electron microscopy, Raman spectroscopy, and molecular phylogenetic approaches were used. The HAB area was estimated by the spectral analysis of satellite-derived imagery. The causative organisms were unarmored dinoflagellates of Karenia species. Their density and biomass reached 100-620 cells·mL-1 and 1300-7700 mg·m-3, respectively, which accounted for 31-99% of the total cell density and 82-99% of the total phytoplankton biomass in late September to mid-October. The dominant species was Karenia selliformis, and the other co-occurring kareniacean species were K. cf. cristata, K. mikimotoi, K. papilionacea, K. longicanalis, and two unidentified morphotypes of Karenia spp. The molecular phylogeny inferred from LSU rDNA and ITS region showed that K. selliformis from Kamchatka in 2020 belonged to the cold-water group I and was identical to K. selliformis strains from Hokkaido, Japan, identified in 2021. This is the first HAB event caused by K. selliformis recorded from Russian coastal waters.

Coral Holobionts Possess Distinct Lipid Profiles That May Be Shaped by Symbiodiniaceae Taxonomy.

Symbiotic relationships are very important for corals. Abiotic stressors cause the acclimatization of cell membranes in symbionts, which possess different membrane acclimatization strategies. Membrane stability is determined by a unique lipid composition and, thus, the profile of thylakoid lipids can depend on coral symbiont species. We have analyzed and compared thylakoid lipidomes (mono- and digalactosyldiacylglycerols (MGDG and DGDG), sulfoquinovosyldiacylglycerols (SQDG), and phosphatidylglycerols (PG)) of crude extracts from symbiotic reef-building coral Acropora sp., the hydrocoral Millepora platyphylla, and the octocoral Sinularia flexibilis. S. flexibilis crude extracts were characterized by a very high SQDG/PG ratio, a DGDG/MGDG ratio < 1, a lower degree of galactolipid unsaturation, a higher content of SQDG with polyunsaturated fatty acids, and a thinner thylakoid membrane which may be explained by the presence of thermosensitive dinoflagellates Cladocopium C3. In contrast, crude extracts of M. platyphylla and Acropora sp. exhibited the lipidome features of thermotolerant Symbiodiniaceae. M. platyphylla and Acropora sp. colonies contained Cladocopium C3u and Cladocopium C71/C71a symbionts, respectively, and their lipidome profiles showed features that indicate thermotolerance. We suggest that an association with symbionts that exhibit the thermotolerant thylakoid lipidome features, combined with a high Symbiodiniaceae diversity, may facilitate further acclimatization/adaptation of M. platyphylla and Acropora sp. holobionts in the South China Sea.

Lipidomes of phylogenetically different symbiotic dinoflagellates of corals.

The structural base of all membranes of symbiotic dinoflagellates (SD) is composed of glycolipids and betaine lipids, whereas triacylglycerols (TG) constitute an energy reserve and are involved in biosynthesis of glycolipids. Since data on the SD lipidome and the host's influence on symbionts' lipidome are scanty, we analyzed and compared the lipidomes of SD isolated from the zoantharian Palythoa tuberculosa and the alcyonarian Sinularia heterospiculata. A sequencing of nuclear gene regions showed that both cnidarians hosted the dinoflagellates Cladocopium sp. (subclades C1 and C3), but the zoantharian also contained the dinoflagellates Durusdinium trenchii (clade D). The presence of the thermotolerant D. trenchii resulted in a higher unsaturation of mono- and digalactosyldiacylglycerols (MGDG and DGDG), but a lower unsaturation of sulfoquinovosyldiacylglycerol (SQDG). The same features were earlier described for same SD from a reef-building coral. Hence, the profile of glycolipid molecules, which form SD thylakoid membranes, seems to be species-specific and does not depend on the host's taxonomic position. In contrast, the betaine lipid molecular species profile of diacylglyceryl-3-O-carboxyhydroxymethylcholine (DGCC), which forms SD cell membranes, can be influenced by the host. The profiles of the TG molecular species from freshly isolated SD have been determined for the first time. These molecular species can be divided on the basis of the acyl group in sn-2 position. The TG with 16:0 acyl group in sn-2 position may enrich total TG of a cnidarian colony and originate from SD cytoplasm. In contrast, TG 18:3/18:4/18:3 may be biosynthetically related with DGDG and concentrated in SD plastoglobules. Our data may be useful for further investigations of natural and technogenic variations in microalgal lipids and symbiont-host interactions in marine ecosystems.

Isolation, characterization, and ecotoxicological application of marine mammal skin fibroblast cultures.

Marine mammal cell cultures are a multifunctional instrument for acquiring knowledge about life in the world's oceans in physiological, biochemical, genetic, and ecotoxicological aspects. We succeeded in isolation, cultivation, and characterization of skin fibroblast cultures from five marine mammal species. The cells of the spotted seal (Phoca largha), the sea lion (Eumetopias jubatus), and the walrus (Odobenus rosmarus) are unpretentious to the isolation procedure. The sea otter (Enhydra lutris) fibroblasts should be isolated by trypsin disaggregation, while only mechanical disaggregation was suitable for the beluga whale (Delphinapterus leucas) cells. The cell growth parameters have been determined allowing us to find the optimal seeding density for continuous and effective cultivation. The effects of nonpathogenic algal extracts on proliferation, viability, and functional activity of marine mammal cells in vitro have been presented and discussed for the first time.

The tellurite-reducing bacterium Alteromonas macleodii from a culture of the toxic dinoflagellate Prorocentrum foraminosum.

The Alteromonas macleodii strain 2328 was isolated from a clonal culture of the toxic dinoflagellate Prorocentrum foraminosum. The strain exhibits a resistance to high K2TeO3 concentrations (2500 µg/mL). A study of the growth dynamics of the strain exposed to K2TeO3 has shown a longer lag phase and a reduced stationary phase compared to those during cultivation with no toxicant. The fatty acids profile is dominated by 16:1 (n-7), 16:0, 17:1, 15:0, 18:1 (n-7), and 17:0. The 2328 strain belongs to the Gammaproteobacteria and is related to the genus Alteromonas with 99-100% sequence similarity to some intra-genome allele variants (paralogues) of 16S rRNA from A. macleodii. A phylogenetic reconstruction (ML and NJ), based on HyHK amino acid sequences, has revealed that the analyzed 2328 strain forms a common cluster with A. macleodii strains. In the presented work, the ability of A. macleodii to reduce potassium tellurite to elemental tellurium has been recorded for the first time. Bacteria reduce potassium tellurite to Te (0), nanoparticles of which become distributed diffusely and in the form of electron-dense globules in cytoplasm. Large polymorphous metalloid crystals are formed in the extracellular space. Such feature of the A. macleodii strain 2328 makes it quite attractive for biotechnological application as an organism concentrating the rare metalloid.

New morphological data and molecular phylogeny of the benthic dinoflagellate Pseudothecadinium campbellii (Dinophyceae, Gonyaulacales).

Pseudothecadinium campbellii, a phototrophic, thecate, marine benthic species, has been found in the Sea of Japan, Russia. The morphological description of the species has been emended, and the thecal tabulation pattern is now APC 4' 2a 4″ 6c 6 s 5‴ 1⁗. Our study indicates that P. campbellii is related to Thecadinium kofoidii and Thecadiniopsis tasmanica, based on a unique morphological feature: incomplete precingular plate series. Previously, molecular data was not available for the taxa, and thus the phylogenetic position of P. campbellii within the Dinophyceae remained obscure. In this study, analyses of the rRNA gene sequences (partial 18S and 28S) revealed that unexpectedly, P. campbellii is most closely related to Halostylodinium arenarium. It formed a common clade with the Thecadinium sensu stricto clade comprising T. kofoidii and T. pseudokofoidii. This clade was placed within the order Gonyaulacales. However, almost no similarity in morphology was found between the two genetically closest species. In addition, they have different lifestyles: unlike P. campbellii, the nonmotile stage is dominant in the life cycle of H. arenarium. It has been shown that other genetically similar species (T. kofoidii, T. pseudokofoidii, T. yashimaense) exhibited some morphological features that unite them with gonyaulacoids.

Detection of Dinophysistoxin-1 in Clonal Culture of Marine Dinoflagellate Prorocentrum foraminosum (Faust M.A., 1993) from the Sea of Japan.

For the first time the presence of dinophysistoxin-1 (DTX-1) in a culture of Prorocentrum foraminosum was revealed in cells and in the culture medium. The clone was isolated from coastal waters of the Sea of Japan and identified by molecular analyses of SSU and D1/D2 regions of LSU rDNA. The concentration of DTX-1 in cells was 8.4 ± 2.5 pg/cell and, in cell-free media, 27.9 ± 14.7 µg/L. The toxin presence was confirmed by HPLC with high-resolution tandem mass-spectrometry.