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Julius Lukes - One of the best experts on this subject based on the ideXlab platform.

  • unique dynamics of paramylon storage in the marine Euglenozoan diplonema papillatum
    Protist, 2020
    Co-Authors: Ingrid Skodovasverakova, Kristína Záhonová, Julius Lukes, Galina Prokopchuk, Priscila Penadiaz, Martin Moos, Anton Horvath, Petr Simek
    Abstract:

    Diplonemids belong to the most diverse and abundant marine protists, which places them among the key players of the oceanic ecosystem. Under in vitro conditions, their best-known representative Diplonema papillatum accumulates in its cytoplasm a crystalline polymer. When grown under the nutrient-poor conditions, but not nutrient-rich conditions, D. papillatum synthesizes a β-1,3-glucan polymer, also known as paramylon. This phenomenon is unexpected, as it is in striking contrast to the accumulation of paramylon in euglenids, since these related flagellates synthesize this polymer solely under nutrient-rich conditions. The capacity of D. papillatum to store an energy source in the form of polysaccharides when the environment is poor in nutrients is unexpected and may contribute to the wide distribution of these protists in the ocean.

  • Life Cycle, Ultrastructure, and Phylogeny of New Diplonemids and Their Endosymbiotic Bacteria
    'American Society for Microbiology', 2018
    Co-Authors: Daria Tashyreva, Ales Horak, Galina Prokopchuk, Akinori Yabuki, Jan Votýpka, Julius Lukes
    Abstract:

    ABSTRACT Diplonemids represent a hyperdiverse and abundant yet poorly studied group of marine protists. Here we describe two new members of the genus Diplonema (Diplonemea, Euglenozoa), Diplonema japonicum sp. nov. and Diplonema aggregatum sp. nov., based on life cycle, morphology, and 18S rRNA gene sequences. Along with Euglenozoan apomorphies, they contain several unique features. Their life cycle is complex, consisting of a trophic stage that is, following the depletion of nutrients, transformed into a sessile stage and subsequently into a swimming stage. The latter two stages are characterized by the presence of tubular extrusomes and the emergence of a paraflagellar rod, the supportive structure of the flagellum, which is prominently lacking in the trophic stage. These two stages also differ dramatically in motility and flagellar size. Both diplonemid species host endosymbiotic bacteria that are closely related to each other and constitute a novel branch within Holosporales, for which a new genus, “Candidatus Cytomitobacter” gen. nov., has been established. Remarkably, the number of endosymbionts in the cytoplasm varies significantly, as does their localization within the cell, where they seem to penetrate the mitochondrion, a rare occurrence. IMPORTANCE We describe the morphology, behavior, and life cycle of two new Diplonema species that established a relationship with two Holospora-like bacteria in the first report of an endosymbiosis in diplonemids. Both endosymbionts reside in the cytoplasm and the mitochondrion, which establishes an extremely rare case. Within their life cycle, the diplonemids undergo transformation from a trophic to a sessile and eventually a highly motile swimming stage. These stages differ in several features, such as the presence or absence of tubular extrusomes and a paraflagellar rod, along with the length of the flagella. These morphological and behavioral interstage differences possibly reflect distinct functions in dispersion and invasion of the host and/or prey and may provide novel insight into the virtually unknown function of diplonemids in the oceanic ecosystem

  • From simple to supercomplex: mitochondrial genomes of Euglenozoan protists [version 2; referees: 2 approved]
    F1000 Research Ltd, 2016
    Co-Authors: Drahomíra Faktorová, Eva Dobakova, Priscila Peña-diaz, Julius Lukes
    Abstract:

    Mitochondria are double membrane organelles of endosymbiotic origin, best known for constituting the centre of energetics of a eukaryotic cell. They contain their own mitochondrial genome, which as a consequence of gradual reduction during evolution typically contains less than two dozens of genes. In this review, we highlight the extremely diverse architecture of mitochondrial genomes and mechanisms of gene expression between the three sister groups constituting the phylum Euglenozoa - Euglenida, Diplonemea and Kinetoplastea. The earliest diverging euglenids possess a simplified mitochondrial genome and a conventional gene expression, whereas both are highly complex in the two other groups. The expression of their mitochondrial-encoded proteins requires extensive post-transcriptional modifications guided by complex protein machineries and multiple small RNA molecules. Moreover, the least studied diplonemids, which have been recently discovered as a highly abundant component of the world ocean plankton, possess one of the most complicated mitochondrial genome organisations known to date

  • unexpectedly streamlined mitochondrial genome of the Euglenozoan euglena gracilis
    Genome Biology and Evolution, 2015
    Co-Authors: Eva Dobakova, Pavel Flegontov, Julius Lukes, Tomas Skalický
    Abstract:

    In this study, we describe the mitochondrial genome of the excavate flagellate Euglena gracilis. Its gene complement is reduced as compared with the well-studied sister groups Diplonemea and Kinetoplastea. We have identified seven protein-coding genes: Three subunits of respiratory complex I (nad1, nad4, and nad5), one subunit of complex III (cob), and three subunits of complex IV (cox1, cox2, and a highly divergent cox3). Moreover, fragments of ribosomal RNA genes have also been identified. Genes encoding subunits of complex V, ribosomal proteins and tRNAs were missing, and are likely located in the nuclear genome. Although mitochondrial genomes of diplonemids and kinetoplastids possess the most complex RNA processing machineries known, including trans-splicing and editing of the uridine insertion/deletion type, respectively, our transcriptomic data suggest their total absence in E. gracilis. This finding supports a scenario in which the complex mitochondrial processing machineries of both sister groups evolved relatively late in evolution from a streamlined genome and transcriptome of their common predecessor.

  • Schematic tree illustrating currently accepted phylogenetic relationships among Euglenozoan taxa examined in this study.
    2013
    Co-Authors: Gillian H. Gile, Franz B Lang, Gertraud Burger, Julius Lukes, Christina A. Castlejohn, Mark A. Farmer, Drahomíra Faktorová, Patrick J. Keeling
    Abstract:

    The presence of EFL (red) and EF-1α (blue) are traced along the organismal phylogeny to their origins with solid lines where there is phylogenetic evidence for their monophyly. Dotted lines hypothetically trace the presence of EFL back to the ancestor of Euglenozoa. Taxa shown in white text on black background encode EFL; all others encode EF-1α.

Pierre Cardol - One of the best experts on this subject based on the ideXlab platform.

  • atypical composition and structure of the mitochondrial dimeric atp synthase from euglena gracilis
    Biochimica et Biophysica Acta, 2017
    Co-Authors: K Sathish N Yadav, Hector Mirandaastudillo, Lilia Colinatenorio, Fabrice Bouillenne, Herve Degand, Pierre Morsomme, Diego Gonzalezhalphen, Egbert J Boekema, Pierre Cardol
    Abstract:

    Mitochondrial respiratory-chain complexes from Euglenozoa comprise classical subunits described in other eukaryotes (i.e. mammals and fungi) and subunits that are restricted to Euglenozoa (e.g. Euglena gracilis and Trypanosoma brucei). Here we studied the mitochondrial F1FO-ATP synthase (or Complex V) from the photosynthetic eukaryote E. gracilis in detail. The enzyme was purified by a two-step chromatographic procedure and its subunit composition was resolved by a three-dimensional gel electrophoresis (BN/SDS/SDS). Twenty-two different subunits were identified by mass-spectrometry analyses among which the canonical α, β, γ, δ, e, and OSCP subunits, and at least seven subunits previously found in Trypanosoma. The ADP/ATP carrier was also associated to the ATP synthase into a dimeric ATP synthasome. Single-particle analysis by transmission electron microscopy of the dimeric ATP synthase indicated that the structures of both the catalytic and central rotor parts are conserved while other structural features are original. These new features include a large membrane-spanning region joining the monomers, an external peripheral stalk and a structure that goes through the membrane and reaches the inter membrane space below the c-ring, the latter having not been reported for any mitochondrial F-ATPase.

Sittenfeld Appel Ana - One of the best experts on this subject based on the ideXlab platform.

  • Descripción ultraestructural de Euglena pailasensis (Euglenozoa) del Volcán Rincón de la Vieja, Guanacaste, Costa Rica
    'Universidad de Costa Rica', 2016
    Co-Authors: Sanchéz Chacón Ethel, Vargas Montero Maribelle, Mora López Marielos, Ortega, José María, Serrano Aurelio, Freer Bustamante Enrique, Sittenfeld Appel Ana
    Abstract:

    Los euglenoides son eucariotas unicelulares flagelados que habitan ambientes acuáticos y suelos de una gran diversidad de ecosistemas. Este trabajo presenta la descripción morfológica ultraestructural del euglenoide E. pailasensis aislado de las fuentes de lodo caliente de las “pailas de barro” en el Volcán Rincón de la Vieja, Guanacaste, Costa Rica. La temperatura de estos sitios puede variar entre 38 y 98° C y puede tener un pH entre 1 y 4. El estudio se realizó utilizando microscopia electrónica de barrido y transmisión. El euglenoide está constituido por una célula típica que puede medir de 30 a 45 μm de largo y 8-10 μm de ancho, con membrana externa, película, cloroplastos, mitocondrias, núcleo, pigmentos granulares y demás organelas citoplasmáticas de un eucarionte. Esta delimitado por una membrana continua y por una película compuesta de aproximadamente 40 - 90 mionemas que miden entre 0.8 y 1.0 μm de ancho, dispuestas helicoidalmente sobre la célula. Se observó 5 cloroplastos elongados por célula, de 1-2 μm de diámetro y 6-12 μm de largo, delimitados por tres membranas y localizados en la periferia celular. Este posee glóbulos osmiofílicos y un pirenoide penetrado por pocos tilacoides. El material nutritivo se almacena en gránulos de paramilón y las mitocondrias presentan las crestas en disposición radial hacia el interior del lumen. La zona de la ámpula se observó sin flagelo y se notó una red de fibrillas que envuelve el espécimen. Las características ultraestructurales observadas en este estudio, no permiten explicar la capacidad de E. pailasensis para habitar en el ambiente volcánico extremo de las Pailas de Barro Caliente.The euglenoids are unicellular eukaryotic flagellates living in a diversity of soils and aquatic environments and ecosystems. This study describes the ultrastructure of an euglenoid isolated from the surface of a boiling mud pool with temperatures ranging from 38 to 98°C and pH 2 - 4. The hot mud pool is located in Area de Pailas de Barro, Las Pailas, Rincón de la Vieja Volcano, Guanacaste, Costa Rica. The morphological characterization of the Euglena pailasensis was performed by SEM and TEM. It was determined that, although the euglenoid was obtained from an extreme volcanic environment, the general morphology corresponds to that of a typical member of Euglena of 30-45 μm long and 8-10 μm wide, with membrane, pellicle, chloroplasts, mitochondria, nucleus, pigments and other cytoplasmic organelles. E. pailasensis is delimited by a membrane and by 40 to 90 pellicle strips. It was observed up to 5 elongated chloroplasts per cell. The chloroplast contains several osmiophilic globules and a pyrenoid penetrated by few thylakoid pairs. The nutritious material is reserved in numerous small paramylon grains located at the center of the cell, mitocondria are characterized by the presence of crests in radial disposition toward the interior of the lumen. It was also observed around the external surface “pili” like filaments originating from the pellicle strips. There is no evidence for the presence of flagella in the ampulla (reservoir/canal area), a fact confirmed by negative staining, and a difference regarding other species of Euglena. The observed ultrastructural characteristics are not sufficient to explain the adaptation of this species to acid and hot environment

Brian S Leander - One of the best experts on this subject based on the ideXlab platform.

  • Diversity and Evolutionary History of the Symbiontida (Euglenozoa)
    'Frontiers Media SA', 2018
    Co-Authors: Naoji Yubuki, Brian S Leander
    Abstract:

    Several lineages of Euglenozoans are enveloped with epibiotic bacteria and live in low oxygen and anoxic marine sediments, such as Bihospites bacati and Calkinsia aureus. A combination of shared ultrastructural traits and molecular phylogenetic inferences demonstrate that these lineages belong to a clade called the “Symbiontida.” Bihospites and Calkinsia possess all of the synapomorphies for the Euglenozoa plus several novel traits. Bihospites has a distinctive cell surface organization reminiscent of the pellicle strips in euglenids, a robust C-shaped feeding apparatus that encircles the nucleus, and a diverse community of epibiotic bacteria. Calkinsia has a novel “extrusomal pocket” and a thick (orange) extracellular matrix beneath a uniform layer of epibiotic bacteria. Despite the absence of molecular phylogenetic data, similar ultrastructural traits in Postgaardi mariagerensis and its epibiotic bacteria strongly suggest that this species is also a member of the Symbiontida. Molecular phylogenetic trees inferred from small subunit (SSU) ribosomal DNA sequences have shown that Bihospites and Calkinsia group strongly with a diverse set of environmental DNA sequences (eDNA) generated from low-oxygen marine samples collected at different depths from different locations around the world. These data demonstrate a diverse array of symbiontids that have yet to be characterized at the genomic, cellular, and behavior levels, which underscores how poorly we currently understand the biology and ecology of the group. Moreover, current data suggest that the communities of epibiotic bacteria associated with Bihospites, Calkinsia, and Postgaardi co-evolved with their hosts and are metabolically integrated with modified mitochondria positioned immediately beneath the host's plasma membrane. No symbiontid species has ever been cultivated, so improved knowledge about these eukaryotic organisms and their intimate relationships with bacteria in low oxygen environments will likely be achieved using culture-independent approaches, such as isolated-cell metagenomics

  • Image_1_Diversity and Evolutionary History of the Symbiontida (Euglenozoa).TIF
    2018
    Co-Authors: Naoji Yubuki, Brian S Leander
    Abstract:

    Several lineages of Euglenozoans are enveloped with epibiotic bacteria and live in low oxygen and anoxic marine sediments, such as Bihospites bacati and Calkinsia aureus. A combination of shared ultrastructural traits and molecular phylogenetic inferences demonstrate that these lineages belong to a clade called the “Symbiontida.” Bihospites and Calkinsia possess all of the synapomorphies for the Euglenozoa plus several novel traits. Bihospites has a distinctive cell surface organization reminiscent of the pellicle strips in euglenids, a robust C-shaped feeding apparatus that encircles the nucleus, and a diverse community of epibiotic bacteria. Calkinsia has a novel “extrusomal pocket” and a thick (orange) extracellular matrix beneath a uniform layer of epibiotic bacteria. Despite the absence of molecular phylogenetic data, similar ultrastructural traits in Postgaardi mariagerensis and its epibiotic bacteria strongly suggest that this species is also a member of the Symbiontida. Molecular phylogenetic trees inferred from small subunit (SSU) ribosomal DNA sequences have shown that Bihospites and Calkinsia group strongly with a diverse set of environmental DNA sequences (eDNA) generated from low-oxygen marine samples collected at different depths from different locations around the world. These data demonstrate a diverse array of symbiontids that have yet to be characterized at the genomic, cellular, and behavior levels, which underscores how poorly we currently understand the biology and ecology of the group. Moreover, current data suggest that the communities of epibiotic bacteria associated with Bihospites, Calkinsia, and Postgaardi co-evolved with their hosts and are metabolically integrated with modified mitochondria positioned immediately beneath the host's plasma membrane. No symbiontid species has ever been cultivated, so improved knowledge about these eukaryotic organisms and their intimate relationships with bacteria in low oxygen environments will likely be achieved using culture-independent approaches, such as isolated-cell metagenomics.

  • Table_1_Diversity and Evolutionary History of the Symbiontida (Euglenozoa).DOCX
    2018
    Co-Authors: Naoji Yubuki, Brian S Leander
    Abstract:

    Several lineages of Euglenozoans are enveloped with epibiotic bacteria and live in low oxygen and anoxic marine sediments, such as Bihospites bacati and Calkinsia aureus. A combination of shared ultrastructural traits and molecular phylogenetic inferences demonstrate that these lineages belong to a clade called the “Symbiontida.” Bihospites and Calkinsia possess all of the synapomorphies for the Euglenozoa plus several novel traits. Bihospites has a distinctive cell surface organization reminiscent of the pellicle strips in euglenids, a robust C-shaped feeding apparatus that encircles the nucleus, and a diverse community of epibiotic bacteria. Calkinsia has a novel “extrusomal pocket” and a thick (orange) extracellular matrix beneath a uniform layer of epibiotic bacteria. Despite the absence of molecular phylogenetic data, similar ultrastructural traits in Postgaardi mariagerensis and its epibiotic bacteria strongly suggest that this species is also a member of the Symbiontida. Molecular phylogenetic trees inferred from small subunit (SSU) ribosomal DNA sequences have shown that Bihospites and Calkinsia group strongly with a diverse set of environmental DNA sequences (eDNA) generated from low-oxygen marine samples collected at different depths from different locations around the world. These data demonstrate a diverse array of symbiontids that have yet to be characterized at the genomic, cellular, and behavior levels, which underscores how poorly we currently understand the biology and ecology of the group. Moreover, current data suggest that the communities of epibiotic bacteria associated with Bihospites, Calkinsia, and Postgaardi co-evolved with their hosts and are metabolically integrated with modified mitochondria positioned immediately beneath the host's plasma membrane. No symbiontid species has ever been cultivated, so improved knowledge about these eukaryotic organisms and their intimate relationships with bacteria in low oxygen environments will likely be achieved using culture-independent approaches, such as isolated-cell metagenomics.

  • Ultrastructure and molecular phylogenetic position of a novel Euglenozoan with extrusive episymbiotic bacteria: Bihospites bacati n. gen. et sp. (Symbiontida)
    BMC Microbiology, 2010
    Co-Authors: Susana A. Breglia, Naoji Yubuki, Mona Hoppenrath, Brian S Leander
    Abstract:

    Background Poorly understood but highly diverse microbial communities exist within anoxic and oxygen-depleted marine sediments. These communities often harbour single-celled eukaryotes that form symbiotic associations with different prokaryotes. During low tides in South-western British Columbia, Canada, vast areas of marine sand become exposed, forming tidal pools. Oxygen-depleted sediments within these pools are distinctively black at only 2-3 cm depth; these layers contain a rich variety of microorganisms, many of which are undescribed. We discovered and characterized a novel (uncultivated) lineage of heterotrophic Euglenozoan within these environments using light microscopy, scanning and transmission electron microscopy, serial sectioning and ultrastructural reconstruction, and molecular phylogenetic analyses of small subunit rDNA sequences. Results Bihospites bacati n. gen. et sp. is a biflagellated microbial eukaryote that lives within low-oxygen intertidal sands and dies within a few hours of exposure to atmospheric oxygen. The cells are enveloped by two different prokaryotic episymbionts: (1) rod-shaped bacteria and (2) longitudinal strings of spherical bacteria, capable of ejecting an internal, tightly wound thread. Ultrastructural data showed that B. bacati possesses all of the Euglenozoan synapomorphies. Moreover, phylogenetic analyses of SSU rDNA sequences demonstrated that B. bacati groups strongly with the Symbiontida: a newly established subclade within the Euglenozoa that includes Calkinsia aureus and other unidentified organisms living in low-oxygen sediments. B. bacati also possessed novel features, such as a compact C-shaped rod apparatus encircling the nucleus, a cytostomal funnel and a distinctive cell surface organization reminiscent of the pellicle strips in phagotrophic euglenids. Conclusions We characterized the ultrastructure and molecular phylogenetic position of B. bacati n. gen. et sp. Molecular phylogenetic analyses demonstrated that this species belongs to the Euglenozoa and currently branches as the earliest diverging member of the Symbiontida. This is concordant with ultrastructural features of B. bacati that are intermediate between C. aureus and phagotrophic euglenids, indicating that the most recent ancestor of the Symbiontida descended from phagotrophic euglenids. Additionally, the extrusive episymbionts in B. bacati are strikingly similar to so-called "epixenosomes", prokaryotes previously described in a ciliate species and identified as members of the Verrucomicrobia. These parallel symbioses increase the comparative context for understanding the origin(s) of extrusive organelles in eukaryotes and underscores how little we know about the symbiotic communities of marine benthic environments.

  • cascades of convergent evolution the corresponding evolutionary histories of Euglenozoans and dinoflagellates
    Proceedings of the National Academy of Sciences of the United States of America, 2009
    Co-Authors: Julius Lukes, Brian S Leander, Patrick J. Keeling
    Abstract:

    The majority of eukaryotic diversity is hidden in protists, yet our current knowledge of processes and structures in the eukaryotic cell is almost exclusively derived from multicellular organisms. The increasing sensitivity of molecular methods and growing interest in microeukaryotes has only recently demonstrated that many features so far considered to be universal for eukaryotes actually exist in strikingly different versions. In other words, during their long evolutionary histories, protists have solved general biological problems in many more ways than previously appreciated. Interestingly, some groups have broken more rules than others, and the Euglenozoa and the Alveolata stand out in this respect. A review of the numerous odd features in these 2 groups allows us to draw attention to the high level of convergent evolution in protists, which perhaps reflects the limits that certain features can be altered. Moreover, the appearance of one deviation in an ancestor can constrain the set of possible downstream deviations in its descendents, so features that might be independent functionally, can still be evolutionarily linked. What functional advantage may be conferred by the excessive complexity of Euglenozoan and alveolate gene expression, organellar genome structure, and RNA editing and processing has been thoroughly debated, but we suggest these are more likely the products of constructive neutral evolution, and as such do not necessarily confer any selective advantage at all.

Brommund Ulrike - One of the best experts on this subject based on the ideXlab platform.

  • Molekulare Identifizierung und Charakterisierung der Glucosyltransferase EgPaS (Paramylon-Synthase) aus Euglena gracilis (Euglenozoa)
    Bielefeld University, 2004
    Co-Authors: Brommund Ulrike
    Abstract:

    Brommund U. Molekulare Identifizierung und Charakterisierung der Glucosyltransferase EgPaS (Paramylon-Synthase) aus Euglena gracilis (Euglenozoa). Bielefeld (Germany): Bielefeld University; 2004.Der einzellige begeißelte Protist Euglena gracilis synthetisiert das lineare, wasserunlösliche, kristalline beta-1,3-Glucan Paramylon. Das Reservekohlenhydrat wird in Form von membranumschlossenen, hochgeordneten Granula im Cytoplasma der Zellen gespeichert und sowohl von den phototrophen als auch von den meisten heterotrophen Spezies des Taxons Euglenida gebildet. Außerhalb der Euglenida ist das Vorkommen von reinem beta-1,3-Glucan in granulärer Form mit der Funktion einer Energie- und Kohlenstoff-Reserve nicht weit verbreitet: Sowohl die Callose, eine Zellwandkomponente der Höheren Pflanzen, das "Yeast-Glucan" aus Hefe-Zellwänden, das bakterielle Exopolysaccharid Curdlan als auch die in flüssiger Form in Vakuolen gespeicherten Reservekohlenhydrate der Heterokontophyta (Chrysolaminarin und Laminarin) bestehen aus beta-1,6-glycosidisch verzweigten beta-1,3-Glucanen. Während es für die Callose- und die Curdlan-Synthase bereits Sequenzinformationen gibt, liegen für die beta-1,3-Glucan-Synthasen aus Algen und auch für das Enzym aus Euglena gracilis bisher keine molekularen und nur wenige biochemische Untersuchungen vor. Die Paramylon-Synthase (UDP-Glucose:1,3-beta-D-Glucan 3-beta-D-Glucosyltransferase, EC 2.4.1.34) ist Bestandteil eines in der Granula-Membran lokalisierten Multienzym-Komplexes mit einem nativen Molekulargewicht von 669 kDa. Die solubilisierten und isolierten Komplexe synthetisieren in vitro aus UDP-Glucose ein unverzweigtes beta-1,3-Glucan. In dieser Arbeit konnte die substratbindende Untereinheit des Paramylon-Synthase-Komplexes mit einer molekularen Masse von 54 kDa durch Photoaffinitäts-Markierung mit [alpha-32P]-UDP-Glucose identifiziert werden. Das isolierte Protein wurde massenspektrometrisch analysiert und sequenziert. Über das Screening von cDNA-Phagen-Banken von Euglena gracilis sowie RT-PCR und PCR-Analysen konnte die für die Paramylon-Synthase kodierende cDNA-Sequenz und anschließend die vollständige DNA-Sequenz für Euglena gracilis, sowie DNA-Teilsequenzen zweier weiterer Spezies der Gattung Euglena erhalten werden. Das Paramylon-Synthase-Gen egpas kodiert mit seinen 1464 Nukleotiden für ein 487 Aminosäuren großes Protein (EgPaS) mit einer molekularen Masse von 54 kDa, besitzt eine 26 Nukleotide umfassende "spliced leader"-RNA sowie eine mindestens 89 Nukleotide umfassende 3'-UTR (untranslated region). Auf DNA-Ebene konnten vier Introns mit 43, 47, 48 und 153 Nukleotiden identifiziert werden. Die abgeleitete Proteinsequenz wurde als Typ II-Membranprotein klassifiziert und weist einen cytoplasmatischen N-Terminus, eine Transmembran-Helix und eine große, nicht-cytoplasmatisch lokalisierte C-terminale Domäne inklusive eines für Glycosyltransferasen der Superfamilie GT-A typischen DXD-Motives auf. Damit ist die substratbindende Untereinheit des Paramylon-Synthase-Komplexes aus Euglena gracilis eindeutig als zur GT-A-Superfamilie gehörende Glucosyltransferase identifiziert und weist interessanterweise eine grundsätzlich andere Domänenstruktur auf als die bisher bekannten beta-Glucan-Synthasen aus Höheren Pflanzen, Pilzen und Bakterien. Die in dieser Arbeit erzielten Ergebnisse zur Paramylon-Synthase werden in einem Modell veranschaulicht, in dem EgPaS als integrales Membranprotein Bestandteil eines Multi-Protein-Komplexes in der Paramylon-Granula-Membran ist. Als Hypothese für den Ursprung von EgPaS wird ein horizontaler Gentransfer aus einem beta-1,3-Glucan-synthetisierenden vorübergehenden Endocytobionten postuliert