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Solenicola setigera is the first characterized member of the abundant and cosmopolitan uncultured marine stramenopile group MAST-3

Authors

  • Fernando Gómez,

    1. Université Lille Nord de France, Laboratoire d′Océanologie et Géosciences, CNRS UMR 8187, MREN-ULCO, 32 Av. Foch, 62930 Wimereux, France
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  • David Moreira,

    1. Unité d'Ecologie, Systématique et Evolution, CNRS UMR8079, Université Paris-Sud, bâtiment 360, 91405 Orsay, France
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  • Karim Benzerara,

    1. Institut de Minéralogie et de Physique de la Matière Condensée, CNRS UMR 7590, 140 Rue de Lourmel, 75015 Paris, France
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  • Purificación López-García

    Corresponding author
    1. Unité d'Ecologie, Systématique et Evolution, CNRS UMR8079, Université Paris-Sud, bâtiment 360, 91405 Orsay, France
      E-mail puri.lopez@u-psud.fr; Tel. (+33) 169157608; Fax (+33) 1691546 97.
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E-mail puri.lopez@u-psud.fr; Tel. (+33) 169157608; Fax (+33) 1691546 97.

Summary

Culture-independent molecular methods based on the amplification, cloning and sequencing of small-subunit (SSU) rRNA genes are a powerful tool to study the diversity of prokaryotic and eukaryotic microorganisms for which morphological features are not conspicuous. In recent years, molecular data from environmental surveys have revealed several clades of protists lacking cultured and/or described members. Among them are various clades of marine stramenopiles (heterokonts), which are thought to play an essential ecological role as grazers, being abundant and distributed in oceans worldwide. In this work, we show that Solenicola setigera, a distinctive widespread colonial marine protist, is a member of the environmental clade MArine STramenopile 3 (MAST-3). Solenicola is generally considered as a parasite or an epiphyte of the diatom Leptocylindrus mediterraneus. So far, the ultrastructural, morphological and ecological data available were insufficient to elucidate its phylogenetic position, even at the division or class level. We determined SSU rRNA gene sequences of S. setigera specimens sampled from different locations and seasons in the type locality, the Gulf of Lions, France. They were closely related, though not identical, which, together with morphological differences under electron microscopy, suggest the occurrence of several species. Solenicola sequences were well nested within the MAST-3 clade in phylogenetic trees. Since Solenicola is the first identified member of this abundant marine clade, we propose the name Solenicolida for the MAST-3 phylogenetic group.

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