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Protistology ■ 73
microscopic observations and chemical detections of chlorophylls catabolites. Pelagic water samples from the northwestern Pacific were subdivided into hundred milliliter-scale flasks with additions oftrace medium components and/or separately cultured picocyanobacteria as preys and incubated under dim light at 5 to 10 °C. In cultures with additions of Acaryochloris marina, a cyanobacterium (9 = 2-3 ^m; nearly "pico"-scale) that produces chlorophyll d (Chl-d) instead of chlorophyll a (Chl-a) and, 132,173-cyclopheophorbide d enol (a "CPE" derived from Chl-d; cPPB-dE) was detected from the cultures after a few day of incubation. CPEs such as Chl- a-derived cPPB- aE have been reported as non-phototoxic catabolites of chlorophylls and known to be produced by many varieties of protists. Because Chl-d was not detected from any of those samples without addition of A. marina that is allochthonous to the pelagic settings, the occurrence of cPPB-dE in these experiments suggests presence of phycophagic protists that potentially feed on picophytoplanktons. Some flagellates and amoeba were actually observed to have ingested cells of A. marina from microscopic measurements.
CHARACTERIZATION OF STRAIN SRT308; A NEW HETEROTROPHIC FLAGELLATE BASAL TO EUGLENOZOA Shiratori T.1, Yazaki E.2, Inagaki Y.3, Hashimoto T.3, Ishida K.1
1 - Faculty of Life and Environmental Sciences, University of Tsukuba
2 - Graduate School of Life and Environmental Sciences, University of Tsukuba
3 - Center for Computational Sciences, University of Tsukuba
We isolated a new heterotrophic flagellate, strain SRT308 from marine sediment sample collected in Republic of Palau on October 2013. The flagellate is round or oval shape with two long subequal flagella and shows unique rotating motion by beating the both flagella synchronously. Since the morphological combination of the flagellate is unique, the flagellate is apparently a novel lineage of eukaryotes. In molecular phylogenetic analysis using small subunit ribosomal RNA gene sequences, the flagellate shows no strong affinity with major eukaryotic lineages. Large scale phylogenetic analysis using 153 protein-coding genes placed the flagellate at the base of Euglenozoa with strong statistical support, suggesting that the flagellate is a previously undescribed member of the Discoba clade. Consistent with the position inferred from the phylogenomic analysis, the flagellate was found to
share morphological characteristics, namely discoid mitochondrial cristae and parallel basal bodies, with euglenozoans. Furthermore, the flagellate has a euglenozoan-like tripartite flagellar root system, albeit the ventral root splits into two bands, which is similar to the R2 of other typical excavates. On the other hand, the flagellate lacks some englenozoan features, such as pellicle, paraxial rod, non-tubular mastigonemes, or feeding apparatus. Based on these morphological and ultrastructural features, the early character evolution of Englenozoa, as well as that of Discoba as a whole, will be discussed.
VIABLE AMOEBOID PROTISTS FROM THE ARCTIC PERMAFROST Shmakova L.A.
Institute of Physicochemical and Biological Problems in Soil Science, Russian Academy of Sciences [email protected]
Viable amoeboid protists were isolated from the Arctic Late Pleistocene and Holocene permafrost buried soils and sediments. A total of 36 strains of protists of the phylum Amoebozoa have been obtained. Most isolates belong to the genera Acanthamoeba and Flamella. We also isolated Vannella, Cochliopodium, Acramoeba, Phalansterium genera. Many of them belong to new species. Two species belonging to the genus Flamella have been described. They were named Flamella pleistocenica n. sp. and Flamella beringiania n. sp. Two new species of giant Acanthamoeba viruses, Pithovirus sibericum and Mollivirus sibericum, were isolated from buried soil of the age 34 000 years, and described. These are the first representatives of the two new families of Acanthamoeba giant viruses. We isolated amoebas from the permafrost of the age up to 50,000 years. The age ofviable organisms enclosed in the samples corresponds to the time of the last freezing ofthe strata. Mechanisms allowing amoebas to survive such a long cryptobiosis are poorly understood. All amoeba species from permafrost are cyst-forming. We studied the composition of the water extract of trophozoites, unmature, and mature cysts of Acanthamoeba castellanii recovered from permafrost. It was demonstrated that the accumulation of osmolytes such as trehalose, glycerol, tyrosine phosphate, alanine, choline, and a-Glycerophosphocholin occurs during en-cystation. These substances are known to serve as cell protectants during desiccation and freezing. This study directly shows for the first time that amoeba cysts can be conserved not only for years and decades but for many thousand years and then recover, contributing to the formation of an active microbial community.
