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Proteorhodopsin phototrophy in the ocean


Proteorhodopsin1, a retinal-containing integral membrane protein that functions as a light-driven proton pump, was discovered in the genome of an uncultivated marine bacterium; however, the prevalence, expression and genetic variability of this protein in native marine microbial populations remain unknown. Here we report that photoactive proteorhodopsin is present in oceanic surface waters. We also provide evidence of an extensive family of globally distributed proteorhodopsin variants. The protein pigments comprising this rhodopsin family seem to be spectrally tuned to different habitats—absorbing light at different wavelengths in accordance with light available in the environment. Together, our data suggest that proteorhodopsin-based phototrophy is a globally significant oceanic microbial process.

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Figure 1: Laser flash-induced absorbance changes in suspensions of membranes prepared from the prokaryotic fraction of Monterey Bay surface waters.
Figure 2: Laser flash-induced transients at 500 nm of a Monterey Bay bacterioplankton membrane preparation.
Figure 3: Phylogenetic analysis of the inferred amino-acid sequence of cloned proteorhodopsin genes.
Figure 4: Multiple alignment of proteorhodopsin amino-acid sequences.
Figure 5: Absorption spectra of retinal-reconstituted proteorhodopsins in E. coli membranes.

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Data deposits

The sequences have been deposited with GenBank under accession numbers AF349976AF350003.


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We thank J. Zehr and D. Karl for the HOT samples and the captain and crew of the RV Point Lobos for expert assistance at sea. D. Karl and R. Letellier provided spectral irradiance data. This research was supported by the National Science Foundation (E.F.D.), the NIH (J.L.S.), and the David and Lucile Packard Foundation (E.F.D.).

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Correspondence to Edward F. DeLong.

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Béjà, O., Spudich, E., Spudich, J. et al. Proteorhodopsin phototrophy in the ocean. Nature 411, 786–789 (2001).

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