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Ramon Massana
Institut de Ciències del Mar (CSIC), Barcelona
MEDOCEAN meeting, 28 November 2013
Looking for the dominant marine bacterivores
Looking for the dominant marine bacterivores
Smetacek 2002. Nature
Unicellular eukaryotes, colorless, and with flagella
Ubiquitous in the plankton at abundances around 1000 cells ml-1
Most are 1-3 µm in size
Exhibit phylogenetic and functional diversity
Heterotrophic flagellates - Main bacterial grazers
Azam et al. 1983. Mar. Ecol. Progr. Ser
Beyond the simplified microbial loop …
Heterotrophic flagellates as algivorous and osmotrophs
Mixotrophic flagellates as bacterivorous
Viruses as a factor for bacterial mortalityå
5 µm
DAPI-stained epifluorescence microscopyThe only quantitative approachVery poor identification power
Heterotrophic flagellates - Microscopy
The most common in pelagic marine waters (by culturing, enrichments and direct observations)
Stramenopiles Bicosoecida Caecitellus parvulus Cafeteria roenbergensis Boroka karpovii
Chrysopytes Paraphysomonas imperforata Pedinellids Pteridomonas danica
Kinetoplastids Neobodo designis Rynchomonas nasuta
Inserta sedis Ancyromonas sigmoides Amastigomonas debruynei
Paraphysomonas imperforata
Dominates (up to 98% of cells) in flagellate enrichments in the US East Coast
Represents <1% in natural samples
Lim et al. 1999. Limnol. Oceanogr.
Heterotrophic flagellates – Culturing bias
Massana 2011. Annu Rev. Microbiol.
Analysis of 18S rDNA sequences retrieved from the environment
• 40 studies on marine microeukaryotes since 2001
• 8719 environmental sequences
Heterotrophic flagellates – Environmental molecular surveys
Massana 2011. Annu Rev. Microbiol.
Groups with cultured heterotrophic
flagellates
Massana et al. 2002. Appl. Environ. Microbiol.
Massana et al. 2004. Appl. Environ. Microbiol.
Marine Stramenopiles - MAST
(novel, uncultured groups)
MAST-4 as a model heterotrophic flagellate
FISHDAPI10 µm
Massana et al. 2006. Environ. Microbiol.
A bacterivorous heterotrophic picoeukaryote
DAPI FISH Ingested FLB
Grazing rate: 1–3 bacteria h-1
Massana et al. 2009. ISME J.
Bacterial mortality: 1 to 10% of production
MAST-4 as a model heterotrophic flagellate
Widely distributed and abundant
Rodríguez-Martínez et al. 2009. Environ. Microbiol.
q-PCR
FISH
MAST-4 as a model heterotrophic flagellate
Limited genetic diversity
GenBank sequences
MAST-4 as a model heterotrophic flagellate
Global distribution and environmental selection
~550 bp – 123 ARISA fingerprints
Rodríguez-Martínez et al. submitted
MAST-4 as a model heterotrophic flagellate
Rodríguez-Martínez et al. submitted
Global distribution and environmental selection
Summary
The diversity of heterotrophic flagellates is poorly investigated
The culturing bias a main drawnback in the ecology of heterotrophic flagellates
The novel MAST lineages are important marine heterotrophic flagellates
Single Amplified Genomics provide new opportunities for ecological and evolutionary studies
MAST-4 is a nice model of heterotrophic flagellatesWidespread in euphotic waters Accounts for ~10% of cellsActive bacterial grazerLimited diversity (only 5 clades)
AcknowledgmentsInstitut de Ciències del Mar Raquel Rodríguez-Martínez Ramiro Logares Javier del Campo Massimo Pernice Caterina Rodríguez-Giner Irene Forn Vanessa Balagué
Station Biologique de Roscoff, France Fabrice Not Colomban de Vargas
Instituto Tecnológico de Chascomús, Argentina Fernando Unrein
University of Washington, USA Gabrielle Rocap
Bigelow Laboratory for Ocean Sciences, USA Mike Sieracki Ramunas Stepanauskas
you for your attention !