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Protistology ■ 87
organism, which assemble Fe-S clusters in the cytosol by concerted action of SUF and CIA pathways.
SYNCHRONIZED AND ER-DEPENDENT DYNAMICS OF MITOSOMES Voleman L.1, Najdrova V.1, Astvaldsson A.2, Tumova P.3, Einarsson E.2, Svindrych Z.4, Hagen G.M.4, Tachezy J.1, Svard S.G.2, Dolezal P.1
1 - BIOCEV— Biotechnology andBiomedicine Center of the Academy of Sciences and Charles University in Vestec and Department of Parasitology, Faculty of Science, Charles University in Prague, Czech Republic
2 - Department ofCell and Molecular Biology, BMC, Uppsala University, Uppsala, Sweden
3 - Department of Tropical Medicine, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic
4 - Institute of Cellular Biology and Pathology, First Faculty of Medicine, Charles University in Prague, Czech Republic [email protected]
Mitosomes are the smallest evolutionary forms of mitochondria that evolved in eukaryotes adapted to anaerobic environments. While abandoning many attributes of the aerobic mitochondria such as the genome, respiration and the cristae, mitosomes have retained the double membrane and the bare bones of the pathways for the protein import and the synthesis ofthe iron-sulfur clusters. Here, we studied the dynamics of the mitosomes in the parasitic protist Giardia intestinalis, which belongs to one of five supergroups of eukaryotes known as Excavata. We found that mitosomes are extremely steady organelles during the interphase undergoing neither the fission nor the fusion during the interphase, thus being highly prone to become heterogeneous. Surprisingly, the mitosomal division is restricted to mitosis, when both central and peripheral organelles divide in a synchronized manner. The mitosomes also divide during the encystation of the parasite, thus preconfigure the cyst for the rapid excystation in a new host. Interestingly, the division involves the association of the mitosomes with the endoplasmic reticulum, a relationship typical for the mitochondria of Opisthokonta. While several such tethering mechanisms, which enable lipid transfer between the organelles, have been described for Opisthokonta, none of these have been shown to function in other eukaryotic supergroups including Excavata. However, we were able to show that lipid enzyme long chain acyl-CoA synthetase 4 is distributed to the mitosome-ER interface.
MORPHOLOGICAL AND MOLECULAR INVESTIGATION OF MARINE PARAMOEBI-DAE (AMOEBOZOA, DACTYLOPODIDA) Volkova E.N., Kudryavtsev A.A. Saint Petersburg State University, Russia [email protected]
We present a revision of marine dactylopodid amoebae containing an intracellular eukaryotic symbiont traditionally called 'parasome', and currently known as 'Perkinsela-like organism' (PLO) related to Kinetoplastida. This group traditionally consists of two genera: Paramoeba Schaudinn, 1896 and Neoparamoeba Page, 1987 which differ in their cell coat structure; the former being covered with scales, while the latter, with the thin, scaleless glycocalyx. The third PLO-containing genus, Janickina Chatton, 1953 has no clear taxonomic affinities yet, as no molecular data are available for its members. We present the results of investigation of the biodiversity and phylogenetic relationships within the genera Paramoeba and Neoparamoeba based on 15 marine and brackish water strains isolated from a broad range ofhabitats. The conclusions are based on morphological, ultrastructural and molecular evidence. The data obtained allow us to conclude that (1) Morpho-species of Paramoeba and Neoparamoeba show considerable levels of intragenomic and intraspecies variability based on the SSU rDNA and ITS region sequences; (2) A detailed study combining analysis of light-microscopic data, ultrastructure and molecular evidence is necessary in most of cases to discriminate species within this group; (3) The cell coats of Paramoeba/Neoparamoeba clade have evolved from the scale-bearing ancestral taxa through several independent scale losses in various lineages of this clade. We also present novel data that contribute to further understanding of the co-evolution of amoebae and their intracellular symbionts.
Partially supported by the RFBR grant 15-29-02749; the study utilized the equipment of the core facility centers of St. Petersburg State University.
CILIATES AS BIOINDICATORS OF MARINE WATER QUALITY Warren A.1, Xu H.2
1 - Department of Life Sciences, Natural History Museum, London, UK
2 - Laboratory ofMicrobialEcology, Ocean University of China, Qingdao, China [email protected]
Although protists, and especially ciliates, have long
88 • "PROTIST—2016
been used as indicators of freshwater quality, they are rarely used in this capacity in marine waters. Here I will summarize the results of a series of studies carried out in Jiaozhou Bay, on the Yellow Sea coast of NE China, in which we investigate the relationships between ciliate communities, both planktonic and periphytic, and certain physico-chemical parameters that varied at different sites within the Bay. In each study, ciliates were identified and enumerated by direct microscopy, and data were analyzed using various statistical packages mainly within PRIMER. A main aim of this investigation was to develop protocols that maximize the efficiency of sampling and analyses of the ciliate communities. Our main findings were: (1) the 8-sampling events per year may be an optimal sampling strategy for planktonic ciliated protozoan seasonal research in marine ecosystems; (2) 90% of the periphytic community could be recovered on 10 microscope slide replicates immersed at one depth for 3 — 21 days; (3) multivariate (step-best-matching) analysis allows a subset of the most reliable indicator species to be identified without losing accuracy of water quality prediction; (4) applying taxonomic efficiency, i.e., identifying to the highest rank without losing critical bioindicator information, revealed that genus-level identification allows for accurate prediction of water quality; (5) efficiencies of sample analyses can be achieved by omitting ubiquitous groups, and using presence/ absence of others rather than abundance data.
SPECIES CLASSIFICATION AND MATING IN FORAMINIFERA
Weiner A.K.M., Tsuchiya M., Toyofuku T., Kitazato H.
JAMSTEC, Japan Agency for Marine Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka 237-0061, Kanagawa, Japan [email protected]
Many groups of foraminifera are characterized by the formation of elaborate shells, which provide detailed morphological features, useful for species classification. Since the majority of works focuses on their fossilized shells, a comprehensive morphotaxonomy has been established. Yet, genetic analyses revealed an even higher diversity on the molecular level, hidden within the traditional morphospecies. These cryptic species are marked by large genetic distances and differentiated distribution patterns, implying that cryptic species rather than morphospecies represent the level of species. As a consequence, today we are facing a conflict between the morphological species concept and the interpretation of genetic diversity. The
biological meaning of both is still unclear and the relationship between genetic divergence and the level of species or populations remains uncertain. In order to overcome this conflict, we try to combine aspects of morphological variability, genetic diversity and reproduction to achieve an integrative approach for species delimitation in foraminifera. To this end, we carry out breeding experiments on benthic foraminifera to observe the mating behavior between genetically divergent lineages to detect the level of divergence that corresponds to reproductive isolation. In addition, we plan to observe the mating behavior among genetically homogenous populations to examine the existence of different mating types within a population. The mating system largely influences the generation of genetic variation and contributes to the process of adaptation. Understanding its mechanisms in foraminifera is thus essential to understand the diversification and evolution of the group.
THE EVOLUTION OF MITOCHONDRIAL MEMBRANE CONTACT SITES Wideman J.G.
Department ofBiosciences, University ofExeter, United Kingdom
[email protected] It is commonly accepted that mitochondria evolved from an alpha-proteobacterial endosymbiont to become the major energy producing organelle of the eukaryote cell. Accounts describing the integration of the pre-mitochondrial symbiont into host cell processes often focus on this transfer of the control of energy production from the symbiont to the host. However, mitochondria are more than mere ATP generators and have several physical and functional links to various cell systems. One such link is manifested in the physical and functional link between mitochondria and the endomembrane system in the form of membrane contact sites (MCSs). These MCSs are important for non-vesicular lipid transport between apposed membranes. Recent progress has identified the protein complexes responsible for maintaining MCSs in Saccharomyces cerevisiae. A surprising number of functionally overlapping mitochondrial MCS tethering complexes have been described, but the extent to which MCS tethers are conserved between distant lineages appears to vary. Thus, while being functionally redundant in S. cerevisiae, MCSs appear to have a high degree of evolutionary plasticity in eukaryotes. Taken together, these data suggest that the last eukaryote common ancestor had a mitochondrion highly connected to diverse endomembranes, but over the course of eukaryote
