Identifying protist consumers of photosynthetic picoeukaryotes in the surface ocean using stable isotope probing

Orsi, William D. (Horn Point Laboratory, University of Maryland Center for Environmental Science, Cambridge, MD 21613, USA) ; Wilken, Susanne (Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA) ; del Campo, Javier (Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada) ; Heger, Thierry (School of Viticulture and Enology, HES-SO // University of Applied Sciences Western Switzerland) ; James, Erick (Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada) ; Richards, Thomas A. (Department of Biosciences, University of Exeter, Geoffrey Pope Building, Exeter, EX4 4QD, UK) ; Keeling, Patrick J. (Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada) ; Worden, Alexandra Z. (Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA) ; Santoro, Alyson E. (Horn Point Laboratory, University of Maryland Center for Environmental Science, Cambridge, MD 21613, USA)

Photosynthetic picoeukaryotes contribute a significant fraction of primary production in the upper ocean. Micromonas pusilla is an ecologically relevant photosynthetic picoeukaryote, abundantly and widely distributed in marine waters. Grazing by protists may control the abundance of icoeukaryotes such as M. pusilla, but the diversity of the responsible grazers is poorly understood. To identify protists consuming photosynthetic picoeukaryotes in a productive North Pacific Ocean region, we amended seawater with living 15N, 13C-labelled M. pusilla cells in a 24-h replicated bottle experiment. DNA stable isotope probing, combined with high-throughput sequencing of V4 hypervariable regions from 18S rRNA gene amplicons (Tag-SIP), identified 19 operational taxonomic units (OTUs) of microbial eukaryotes that consumed M. pusilla. These OTUs were distantly related to cultured taxa within the dinoflagellates, ciliates, stramenopiles (MAST-1C and MAST-3 clades) and Telonema flagellates, thus, far known only from their environmental 18S rRNA gene sequences. Our discovery of eukaryotic prey consumption by MAST cells confirms that their trophic role in marine microbial food webs includes grazing upon picoeukaryotes. Our study provides new experimental evidence directly linking the genetic identity of diverse uncultivated microbial eukaryotes to the consumption of picoeukaryotic phytoplankton in the upper ocean.


Article Type:
scientifique
Faculty:
Ingénierie et Architecture
School:
Changins
Subject(s):
Ingénierie
Date:
2017-12
Pagination:
13 p.
Published in:
Environmental Microbiology
Numeration (vol. no.):
2018, 20, 2, pp. 815-827
DOI:
ISSN:
1462-2920
Appears in Collection:

Note: The status of this file is: restricted


 Record created 2018-09-25, last modified 2018-12-20

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