Global biogeography of SAR11 marine bacteria

Authors

  • Mark V Brown,

    1. School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales, Australia
    2. Evolution and Ecology Research Centre, The University of New South Wales, Sydney, New South Wales, Australia
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    • These authors contributed equally to this work
  • Federico M Lauro,

    1. School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales, Australia
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    • These authors contributed equally to this work
  • Matthew Z DeMaere,

    1. School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales, Australia
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  • Les Muir,

    1. CSIRO Marine and Atmospheric Research, Castray Esplanade, Hobart, Tasmania, Australia
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  • David Wilkins,

    1. School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales, Australia
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  • Torsten Thomas,

    1. School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales, Australia
    2. Centre for Marine Bio-Innovation, The University of New South Wales, Sydney, New South Wales, Australia
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  • Martin J Riddle,

    1. Australian Antarctic Division, Channel Highway, Kingston, Tasmania, Australia
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  • Jed A Fuhrman,

    1. Department of Biological Sciences, Wrigley Institute for Environmental Studies, University of Southern California, Los Angeles, CA, USA
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  • Cynthia Andrews-Pfannkoch,

    1. J. Craig Venter Institute, Rockville, MD, USA
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  • Jeffrey M Hoffman,

    1. J. Craig Venter Institute, Rockville, MD, USA
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  • Jeffrey B McQuaid,

    1. J. Craig Venter Institute, Rockville, MD, USA
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  • Andrew Allen,

    1. J. Craig Venter Institute, Rockville, MD, USA
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  • Stephen R Rintoul,

    1. CSIRO Marine and Atmospheric Research, Centre for Australian Weather and Climate Research—A partnership of the Bureau of Meteorology and CSIRO, and CSIRO Wealth from Oceans National Research Flagship, and the Antarctic Climate and Ecosystems Cooperative Research Centre, Castray Esplanade, Hobart, Tasmania, Australia
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  • Ricardo Cavicchioli

    Corresponding author
    1. School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales, Australia
    • Corresponding author. School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales 2052, Australia. Tel.: +61 2 9385 3516; Fax: +61 2 9385 2742; E-mail: r.cavicchioli@unsw.edu.au

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Abstract

The ubiquitous SAR11 bacterial clade is the most abundant type of organism in the world's oceans, but the reasons for its success are not fully elucidated. We analysed 128 surface marine metagenomes, including 37 new Antarctic metagenomes. The large size of the data set enabled internal transcribed spacer (ITS) regions to be obtained from the Southern polar region, enabling the first global characterization of the distribution of SAR11, from waters spanning temperatures −2 to 30°C. Our data show a stable co-occurrence of phylotypes within both ‘tropical’ (>20°C) and ‘polar’ (<10°C) biomes, highlighting ecological niche differentiation between major SAR11 subgroups. All phylotypes display transitions in abundance that are strongly correlated with temperature and latitude. By assembling SAR11 genomes from Antarctic metagenome data, we identified specific genes, biases in gene functions and signatures of positive selection in the genomes of the polar SAR11—genomic signatures of adaptive radiation. Our data demonstrate the importance of adaptive radiation in the organism's ability to proliferate throughout the world's oceans, and describe genomic traits characteristic of different phylotypes in specific marine biomes.

Synopsis

Metagenomic samples from oceans around the globe were used to examine the biogeography of the dominant marine heterotrophic bacterial clade, SAR11. Analysis uncovers evidence of adaptive radiation in response to environmental parameters, particularly temperature.

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  • By generating 37 new Antarctic metagenomes and analysing the internal transcribed spacer (ITS) regions of the SAR11 clade in a total of 128 surface marine metagenomes, we identified phylotype distributions that strongly correlated with temperature and latitude.
  • By assembling SAR11 genomes from Antarctic metagenome data, we identified specific genes, biases in gene functions and signatures of positive selection in the genomes of the polar SAR11—genomic signatures of adaptive radiation.
  • Our data demonstrate the importance of adaptive radiation in an organism's ability to proliferate throughout the world's oceans, and describe genomic traits characteristic of different phylotypes in specific marine biomes.
  • These bacteria are important marine heterotrophs and have a fundamental role in oceanic nutrient cycling. These findings, therefore, have important implications for our ability to predict how changes in ocean temperature may affect bacterial ecology.

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