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The molecular diversity of freshwater picoeukaryotes from an oligotrophic lake reveals diverse, distinctive and globally dispersed lineages

Authors

  • Thomas A. Richards,

    1. Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK.
    2. Department of Zoology, The University of Oxford, South Parks Road, Oxford, OX1 3PS, UK.
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    • These authors contributed equally to this work.

  • Alexey A. Vepritskiy,

    1. Darrin Fresh Water Institute
    2. New York Center for Studies on the Origins of Life, Rensselaer Polytechnic Institute, 5060 Lakeshore Drive, Bolton Landing, NY, USA.
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    • These authors contributed equally to this work.

  • Dilnora E. Gouliamova,

    1. Darrin Fresh Water Institute
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  • Sandra A. Nierzwicki-Bauer

    Corresponding author
    1. Darrin Fresh Water Institute
    2. New York Center for Studies on the Origins of Life, Rensselaer Polytechnic Institute, 5060 Lakeshore Drive, Bolton Landing, NY, USA.
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*E-mail nierzs@rpi.edu; Tel. (+1) 518 644 3541; Fax (+1) 518 644 3640.

Summary

The recent discovery of a diverse phylogenetic assemblage of picoeukaryotes from environments such as oceans, salt marshes and acidic habitats, has expanded the debates about the extent and origin of microbial eukaryotes. However, the diversity of these eukaryote microorganisms, that overlap bacteria in size, and their environmental and biogeographical ubiquity remains poorly understood. Here we survey picoeukaryotes (microbial eukaryotes of 0.2–5 µm in size) from an oligotrophic (nutrient deficient) freshwater habitat using ribosomal RNA gene sequences. Three taxonomic groups the Heterokonta, Cryptomonads and the Alveolata dominated the detected diversity. Most sequences represented previously unsampled species, with several being unassignable to known taxonomic groups and plausibly represent new or unsampled phyla. Many freshwater phylogenetic groups identified in this study appeared unrelated to picoeukaryotic sequences identified in marine ecosystems, suggesting that aspects of eukaryote microbial diversity are specific to certain aquatic environments. Conversely, at least five phylogenetic clusters comprised sequences from freshwater and globally dispersed and often contrasting environments, supporting the concept that a number of picoeukaryotic lineages are widely distributed.

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