Delineating ecologically significant taxonomic units from global patterns of marine picocyanobacteria.
Prochlorococcus and Synechococcus are the two most abundant and widespread phytoplankton in the global ocean. To better understand the factors controlling their biogeography, a reference database of the high-resolution taxonomic marker petB, encoding cytochrome b6, was used to recruit reads out of 109 metagenomes from the Tara Oceans expedition. An unsuspected novel genetic diversity was unveiled within both genera, even for the most abundant and well-characterized clades, and 136 divergent petB sequences were successfully assembled from metagenomic reads, significantly enriching the reference database. We then defined Ecologically Significant Taxonomic Units (ESTUs)-that is, organisms belonging to the same clade and occupying a common oceanic niche. Three major ESTU assemblages were identified along the cruise transect for Prochlorococcus and eight for Synechococcus Although Prochlorococcus HLIIIA and HLIVA ESTUs codominated in iron-depleted areas of the Pacific Ocean, CRD1 and the yet-to-be cultured EnvB were the prevalent Synechococcus clades in this area, with three different CRD1 and EnvB ESTUs occupying distinct ecological niches with regard to iron availability and temperature. Sharp community shifts were also observed over short geographic distances-for example, around the Marquesas Islands or between southern Indian and Atlantic Oceans-pointing to a tight correlation between ESTU assemblages and specific physico-chemical parameters. Together, this study demonstrates that there is a previously overlooked, ecologically meaningful, fine-scale diversity within some currently defined picocyanobacterial ecotypes, bringing novel insights into the ecology, diversity, and biology of the two most abundant phototrophs on Earth.
Sorbonne Universités, Université Paris 06, CNRS, UMR 7144, Station Biologique, CS 90074 Roscoff, France;
Gregory K
GK
Farrant
Sorbonne Universités, Université Paris 06, CNRS, UMR 7144, Station Biologique, CS 90074 Roscoff, France;
Hugo
H
Doré
Department of Marine Biology and Oceanography, Institute of Marine Sciences (ICM), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona ES-08003, Spain;
Francisco M
FM
Cornejo-Castillo
Sorbonne Universités, Université Paris 06, CNRS, UMR 7144, Station Biologique, CS 90074 Roscoff, France;
Frédéric
F
Partensky
Sorbonne Universités, Université Paris 06, CNRS, UMR 7144, Station Biologique, CS 90074 Roscoff, France;
Morgane
M
Ratin
Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW 2109, Australia;
Martin
M
Ostrowski
School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom;
Frances D
FD
Pitt
Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Institut de Génomique, Genoscope, 91057 Evry, France;
Patrick
P
Wincker
School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom;
David J
DJ
Scanlan
Stazione Zoologica Anton Dohrn, 80121 Naples, Italy.
Daniele
D
Iudicone
Department of Marine Biology and Oceanography, Institute of Marine Sciences (ICM), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona ES-08003, Spain;
Silvia G
SG
Acinas
Sorbonne Universités, Université Paris 06, CNRS, UMR 7144, Station Biologique, CS 90074 Roscoff, France; laurence.garczarek@sb-roscoff.fr.
Laurence
L
Garczarek
D059001:Aquatic Organisms / Q000145:classification / Q000235:genetics; D001267:Atlantic Ocean; D001426:Bacterial Proteins / Q000235:genetics*; D014644:Genetic Variation; D019156:Indian Ocean; D048929:Prochlorococcus / Q000145:classification / Q000235:genetics; D046940:Synechococcus / Q000145:classification / Q000235:genetics
D001426:Bacterial Proteins
Prochlorococcus; Synechococcus; Tara Oceans; metagenomics; molecular ecology