Ultrastructure and 18S rDNA Phylogeny of Apoikia lindahlii comb. nov. (Chrysophyceae) and its Epibiontic Protists, Filos agilis gen. et sp. nov. (Bicosoecida) and Nanos amicus gen. et sp. nov. (Bicosoecida)

Eunsoo Kim, Naoji Yubuki, Brian S. Leander, Linda E. Graham

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Abstract

Three heterotrophic stramenopiles-Apoikia lindahlii comb. nov. (Chrysophyceae), Filos agilis gen. et sp. nov. (Bicosoecida), and Nanos amicus gen. et sp. nov. (Bicosoecida)-were isolated from acidic peat bogs. The biflagellate A. lindahlii forms loose irregular colonies from which swimming cells may detach, and produces extensive mucilaginous material containing bacterial cells. Phylogenetic analyses of small subunit rDNA sequences demonstrated that A. lindahlii branches within the Chrysophyceae. While A. lindahlii is an obligate heterotroph, ultrastructural observations revealed a leukoplast in the perinuclear region. The pico-sized uniflagellates F. agilis and N. amicus were isolated from separate lakes and within the mucilage of A. lindahlii, suggesting their close associations in natural habitats. In SSU rDNA phylogenies, F. agilis and N. amicus were closely related to the bicosoecids Adriamonas, Siluania, Paramonas, and Nerada. While Filos, Nanos, and Siluania are similar in light microscopic features, their SSU rDNA gene sequences differed significantly (>8% differences) and were not monophyletic. Both F. agilis and N. amicus have a cytostome/cytopharynx particle ingestion apparatus. Bacterial cells and material similar to the mucilage of A. lindahlii occurred within the food vacuole of F. agilis and N. amicus. The nature of association between A. lindahlii and its epibiontic bicosoecids is discussed.

Original languageEnglish
Pages (from-to)177-196
Number of pages20
JournalProtist
Volume161
Issue number2
DOIs
StatePublished - Apr 2010

Bibliographical note

Funding Information:
This research was supported by grant MCB-9977903 from the National Science Foundation and an Anna Grant Birge Memorial Award (University of Wisconsin-Madison). This work was also supported by grants to BSL from the Tula Foundation (Centre for Microbial Diversity and Evolution), the National Science and Engineering Research Council of Canada (NSERC 283091-09 ) and the Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity. The authors also thank J. Graham (University of Wisconsin-Madison) for help with the TEM preparation of Filos and Nanos ; L. Wilcox (University of Wisconsin-Madison) for helpful discussions; C. Sattler (University of Wisconsin-Madison), R. Wise and T. Kostman (University of Wisconsin-Oshkosh) for technical advice; K. Elliot (University of Wisconsin-Madison) for help with illustrations; R. Kowal (University of Wisconsin-Madison) for edition of Latin descriptions; and the University of Chicago for access to print journals in the John Crerar Library.

Keywords

  • Apoikia
  • Bicosoecida
  • Chrysophyceae
  • Filos
  • Nanos
  • stramenopiles

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