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 !