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40 • "PROTIST—2016
pathogenic forms associated with damaged corals undergoing disease conditions, such as Brown Band disease. These altered communities are characterized by rapid tissue breakdown in hard corals, coupled with high levels of dissolved organic matter. Samples were taken by direct capture, observed with phase contrast and epifluorescence microscopy, recorded by video and photomicrography, and fixed for later identification and genomic studies. The relative abundance of diatoms/flagellates/ ciliates appears to show a higher proportion of photosynthetic species as compared to previous observations. Brown Band ciliates were not found on the corals, in the sediments, on algal surfaces, or in the plankton prior to bleaching in late January, posing the question oftheir location when not acting as opportunistic pathogens.
"CANDIDATUS MEGAIRA": AN EMERGING GENUS OF BACTERIAL ENDOSYMBIONTS WIDESPREAD IN CILIATES AND OTHER PROTISTS
Lanzoni O.1, Shaidullina A.2, Sabaneyeva E.2, Castelli M.1,3, Lebedeva N.4, Potekhin A.2, Petroni G.1
1 - Department of Biology, University of Pisa, Pisa, Italy
2 - Faculty ofBiology, St. Petersburg State University, Saint Petersburg, Russia
3 - Department of Veterinary Medicine, University of Milan, Milan, Italy
4 - Centre of Core Facilities "Culture Collections of Microorganisms", St Petersburg State University, Saint Petersburg, Russia [email protected]
" Candidatus Megaira" (Rickettsiaceae) is a recently described genus of obligate intracellular bacteria, which are phylogenetically closely related to the pathogen Rickettsia. Sequences representatives of genus " Candidatus Megaira" can be split in at least 3-4 species level sub-clades. These sequences have been found in association to evolutionary far related host lineages (e.g. unicellular and multicellular algae, corals and hydras). The type species of the genus, "Candidatus Megaira polyxenophila", has been found in several ciliates as well as in other protists. In ciliates, " Candidatus Megaira polyxenophila" can infect different cell compartments (macronucleus and cytoplasm) according to the host species. Herein, we provide the characterization of a second "Candidatus Megaira" species inhabiting the cytoplasm ofthe green ciliate Paramecium bursaria. Within the same host cell, this novel " Candidatus Megaira" presents polymorphic features such as the association with endosymbiotic algae, or the possible
presence offlagellum at some stage ofthe life-cycle. Moreover, we performed several trans-infection experiments using different species of newly characterized " Candidatus Megaira" in order to understand how representatives of this genus can be spread in the aquatic environment and how they influence the host fitness within the same ciliate population. We also investigated the interaction between " Candidatus Megaira" and other symbiotic bacteria already inhabiting or invading the same host cell. All together, our findings highlight the necessity of a better understanding of the life-cycles of this widespread, but poorly investigated, endosymbiont.
THE GENOMIC STUDY OF AGAR PRODUCING RED ALGA GRACILARIOPSIS CHORDA Lee J.M.1, Yang E.C.2, Graf L.1, Yoon H.S.1
1 - Department of Biological Sciences, Sungkyunkwan University, Suwon 16419, Korea
2 - Marine Ecosystem Research Division, Korea Institute of Ocean Science & Technology, Ansan, 15627, Korea
Red algae (Rhodophyta) played an important role in the evolution of photosynthetic organisms as plastid donor(s) in chlorophyll-c containing algae including cryptophytes, haptophytes, stramenopiles, and alveolates. Most red algal species are important components in marine ecosystems, serving as a shelter for diverse marine organisms and contributing as primary producers. Many red algal species are heavily cultivating as food and industrial purposes such as agar and carrageenan production. Despite of these importances, only several red algal genomes have been reported among more than 7,000 species. From the major multicellular red algal group of theFlorideophyceae, only one genome was fully sequenced to date. To fill the gap of our understanding on red algae, here we analyzed a new genome of the multicellular red algal species Gracilariopsis chorda, which is one of major cultivar as food and agar production in Korea. Using the long-read single molecule sequencing (PacBio) platform, we completed whole-genome of 89.6 Mbp (49% GC content, 1,098 contigs) that encodes a total of 9,992 predicted proteins. We discuss the interesting story of genome reduction/expansion and gene duplication in red algal genomes at this meeting.
AN ANCESTRAL BACTERIAL DIVISION SYSTEM IS WIDESPREAD IN EUKARYOTIC MITOCHONDRIA
Leger M.M.1, Petru M.2, Zarsky V.2, Eme L.1, Vlcek C.3, Harding T.1, Lang B.F.4, Elias M.5, Dolezal P.2,
