Proteorhodopsin in the ubiquitous marine bacterium SAR11 (original) (raw)

Nature volume 438, pages 82–85 (2005)Cite this article

Abstract

Proteorhodopsins are light-dependent proton pumps that are predicted to have an important role in the ecology of the oceans by supplying energy for microbial metabolism1,2. Proteorhodopsin genes were first discovered through the cloning and sequencing of large genomic DNA fragments from seawater1. They were later shown to be widely distributed, phylogenetically diverse, and active in the oceans3,4,5,6,7. Proteorhodopsin genes have not been found in cultured bacteria, and on the basis of environmental sequence data, it has not yet been possible to reconstruct the genomes of uncultured bacterial strains that have proteorhodopsin genes. Although the metabolic effect of proteorhodopsins is uncertain, they are thought to function in cells for which the primary mode of metabolism is the heterotrophic assimilation of dissolved organic carbon. Here we report that SAR11 strain HTCC1062 (‘_Pelagibacter ubique_’)8, the first cultivated member of the extraordinarily abundant SAR11 clade, expresses a proteorhodopsin gene when cultured in autoclaved seawater and in its natural environment, the ocean. The Pelagibacter proteorhodopsin functions as a light-dependent proton pump. The gene is expressed by cells grown in either diurnal light or in darkness, and there is no difference between the growth rates or cell yields of cultures grown in light or darkness.

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Acknowledgements

We thank J. Nibler and the chemistry department at Oregon State University for the use of the Nd:YAG laser and student laser laboratory facilities; W. Hetherington, R. Letelier, B. Geller and O. Béjà for helpful discussions; and E. L. Barofsky for her assistance with MALDI mass spectrometry. This research was supported by the National Science Foundation, Diversa Corporation and the National Institute of Environmental Health Sciences. Author Contributions S.J.G. led the genome sequencing project, provided the bioinformatics analyses and was the primary writer. L.B. and E.J.M. led the DNA sequencing team at Diversa Corporation. J.-C.C., L.J.W. and H.J.T. provided the growth data. M.D.S. and D.F.B. provided the mass spectrometry analysis. R.D. and S.L. performed the light spectroscopy experiments. K.L.V. cloned the proteorhodopsin gene and showed that it was a light-dependent proton pump, with the assistance of R.D. M.S.R. isolated the Pelagibacter.

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Author notes

  1. Jang-Cheon Cho
    Present address: Department of Oceanography, 5N541, Inha University Younghyun-dong, Nam-Gu, Incheon, 402-751, Korea
  2. Martha D. Stapels
    Present address: Waters Corporation, 34 Maple Street, Milford, Massachusetts, 01757-3696, USA
  3. Michael S. Rappé
    Present address: Hawaii Institute of Marine Biology, SOEST, University of Hawaii, PO Box 1346, Kaneohe, Hawaii, 96744, USA

Authors and Affiliations

  1. Department of Microbiology,
    Stephen J. Giovannoni, Jang-Cheon Cho, Kevin L. Vergin, Michael S. Rappé, Lawrence J. Wilhelm & H. James Tripp
  2. Department of Chemistry,
    Martha D. Stapels & Douglas F. Barofsky
  3. College of Oceanic and Atmospheric Sciences, Oregon State University, 97331, Oregon, Corvallis, USA
    Russell Desiderio & Samuel Laney
  4. Diversa Corporation, 4955 Directors Place, California, 92121-1609, San Diego, USA
    Lisa Bibbs & Eric J. Mathur

Authors

  1. Stephen J. Giovannoni
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  2. Lisa Bibbs
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  3. Jang-Cheon Cho
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  4. Martha D. Stapels
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  5. Russell Desiderio
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  6. Kevin L. Vergin
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  7. Michael S. Rappé
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  8. Samuel Laney
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  9. Lawrence J. Wilhelm
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  10. H. James Tripp
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  11. Eric J. Mathur
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  12. Douglas F. Barofsky
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Corresponding author

Correspondence toStephen J. Giovannoni.

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Competing interests

The HTCC1062 proteorhodopsin gene sequence has been deposited in GenBank under accession number CP000084. Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

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Giovannoni, S., Bibbs, L., Cho, JC. et al. Proteorhodopsin in the ubiquitous marine bacterium SAR11.Nature 438, 82–85 (2005). https://doi.org/10.1038/nature04032

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Editorial Summary

SAR11: basking in the light

Proteorhodopsin genes were discovered, as DNA fragments in sea water, long before anybody knew what organisms they came from. They encode light-dependent proton pumps that are thought to have a central role in ocean ecology by supplying the energy for microbial metabolism, and now the intact proteorhodopsin system has been tracked down. It is found in SAR11, one of the most abundant organisms on the planet. SAR11, recently renamed Pelagibacter ubique, was synonymous with uncultured microbial diversity until it was first cultured in 2002. These organisms have proteorhodopsin proton pumps and have the odd (for a light-gatherer) ability to grow equally as well in the dark as in the light. SAR11 is out there in the oceans competing with the likes of cyanobacteria for a niche amongst the bacterioplankton. Now it seems that the cyanobacteria may have outside assistance. Viruses (or phages) that infect the ubiquitous cyanobacteria Prochlorococcus do more than just use their DNA to force the host to make more phage. The viral genome contains photosynthesis genes, possibly captured from cyanobacterial hosts long ago. These encode proteins that combine with host photosynthetic machinery to ensure that the host provides the phage with the energy necessary to produce phage progeny.