Bacterial Rhodopsin: Evidence for a New Type of Phototrophy in the Sea

Science. 2000 Sep 15;289(5486):1902-6. doi: 10.1126/science.289.5486.1902.


Extremely halophilic archaea contain retinal-binding integral membrane proteins called bacteriorhodopsins that function as light-driven proton pumps. So far, bacteriorhodopsins capable of generating a chemiosmotic membrane potential in response to light have been demonstrated only in halophilic archaea. We describe here a type of rhodopsin derived from bacteria that was discovered through genomic analyses of naturally occuring marine bacterioplankton. The bacterial rhodopsin was encoded in the genome of an uncultivated gamma-proteobacterium and shared highest amino acid sequence similarity with archaeal rhodopsins. The protein was functionally expressed in Escherichia coli and bound retinal to form an active, light-driven proton pump. The new rhodopsin exhibited a photochemical reaction cycle with intermediates and kinetics characteristic of archaeal proton-pumping rhodopsins. Our results demonstrate that archaeal-like rhodopsins are broadly distributed among different taxa, including members of the domain Bacteria. Our data also indicate that a previously unsuspected mode of bacterially mediated light-driven energy generation may commonly occur in oceanic surface waters worldwide.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aerobiosis
  • Amino Acid Sequence
  • Archaea / classification
  • Archaea / physiology
  • Bacteria / genetics
  • Bacterial Physiological Phenomena*
  • Cloning, Molecular
  • Escherichia coli
  • Gammaproteobacteria / classification
  • Gammaproteobacteria / genetics
  • Gammaproteobacteria / physiology*
  • Molecular Sequence Data
  • Oceans and Seas
  • Photochemistry
  • Photosynthesis
  • Phylogeny
  • Phytoplankton / genetics
  • Phytoplankton / physiology
  • Protein Binding
  • Proton Pumps / physiology
  • Retinaldehyde / metabolism
  • Rhodopsin / physiology*
  • Rhodopsins, Microbial
  • Water Microbiology*


  • Proton Pumps
  • Rhodopsins, Microbial
  • proteorhodopsin
  • Rhodopsin
  • Retinaldehyde