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54 • "PROTIST—2016
is prominent in interphase, was disappeared and chromosomes were scattered in the nucleus. The newly formed shell was almost or fully constructed when the nuclear division reaches metaphase. In this phase, the spindle body was formed and the chromosomes were arranged at the equatorial plane randomly. At the time of completion of shell construction, the nucleus was observed to be in anaphase, and chromosomes were separated into anterior and posterior side of the nucleus. After the migration of a daughter cell into new shell, the nucleus with densely condensed chromosomes was observed to locate at posterior end of each daughter cell.
MITOSOMES IN ENTAMOEBA HISTOLYTICA. DIFFERENTIATION, METABOLITE TRANSPORT, AND FISSION Nozaki T.12
1 - National Institute of Infectious Diseases
2 - University of Tsukuba [email protected]
Hydrogenosomes and mitosomes are mitochondrion-related organelles (MROs) in anaerobic/ microaerophilic eukaryotes with highly reduced and divergent functions. Entamoeba possesses a highly divergent MRO known as the mitosome. The biological functions and their origin of Entamoeba mitosomes have been a longstanding enigma in the evolution of mitochondria. We previously demonstrated that sulfate activation, which is not generally compartmentalized to mitochondria, is a major function of E. histolytica mitosomes. We recently purified and identified cholesteryl sulfate (CS) as a final sulfate activation metabolite. We further identified the gene encoding the cholesteryl sulfotransferase responsible for synthesis of CS. Supplementation of CS to the culture increased the number of cysts, while, conversely, chlorate, a selective inhibitor of the first enzyme in the sulfate activation pathway, inhibited cyst formation. These results indicate that CS plays an important role in differentiation, an essential process for transmission of Entamoeba between hosts. Furthermore, Mastigamoeba balamuthi, an anaerobic, free-living amoebozoan species, also has the sulfate activation pathway in MROs, but does not possess the capacity for CS production. Hence, we proposed that a unique function of MROs in Entamoeba contributes to adaptation of its parasitic life cycle. Understanding of metabolite trafficking across the two mitosomal membranes is important to understand metabolic functions ofmitosomes. We recently discovered a novel mitosomal P-barrel outer membrane protein of30 kDa (MBOMP30) and several novel membrane-spanning
proteins from a list of the mitosome proteome. We experimentally confirmed their localization and integration to mitosome membranes by Percoll-gradient fractionation, carbonate fractionation, immunofluorescence assay, and immunoelectron microscopy. These new class ofmitosomal membrane proteins including MBOMP30 likely play unique and indispensable roles in Entamoeba mitosomes. We also found that two dynamin-related proteins, DrpA and DrpB, are involved in mitosome fission. Expression of a mutant form or gene silencing of these Drps caused abnormal morphology of mitoses and growth defect, suggesting that mitosome fission is mediated in part by these Drps.
MORPHOLOGY, PHYLOGENY, AND TRANS-CRIPTOME DATA OF A NEW ANAEROBIC METOPUS SPECIES (CILIOPHORA, ARMO-PHORIDA) FROM YANTAI, CHINA Omar A., Zhang Q., Gong J. Laboratory of Microbial Ecology and Matter Cycles, Yantai Institute of Coastal Zone Research, Chinese Academy ofScience, Yantai, China [email protected]
A new anaerobic Metopus species was discovered in a soil sample from fruit garden in Yantai, China, and investigated using morphological, morphometrical, and molecular methods. The morphology was studied using in vivo observation and protargol impregnation. The main features ofthe new Metopus species include: (i) size in vivo 75-105 * 35-55 ^m; (ii) body shape ellipsoidal to pyriform; (iii) nuclear apparatus invariably in preoral dome, macronucleus reniform, micronucleus globular to ellipsoidal attached to macronucleus; (iv) cytoplasm studied with lipid droplets especially in preoral dome; (v) five perizonal and 18-21 somatic ciliary rows of which three extend onto preoral dome (dome kineties); (vi) three to five distinctly elongated caudal cilia; and (vii) adoral zone composed of 21-29 membranelles and distinctly shorter than perizonal ciliary stripe (45% vs. 61% ofbody length on average). Moreover, this species contains numerous, conspicuous hydrogenosomes, anaerobically-functioning mito-chondrial-related organelles, as an adaptation for the anaerobic lifestyle. SSU rRNA and mRNA were obtained using a single cell transcriptome protocol, and were sequenced with both Sanger and MiSeq Illumina technology. The obtained data were used for phylogenomic analyses and analyzing basic metabolic processes of this anerobic ciliate, including searching for genes ofputative anaerobic-adapting functions.
Supported by the NSFC project 31550110213 and the CAS project 2015PB040.
