Document Detail

Light-powering Escherichia coli with proteorhodopsin.
MedLine Citation:
PMID:  17277079     Owner:  NLM     Status:  MEDLINE    
Proteorhodopsin (PR) is a light-powered proton pump identified by community sequencing of ocean samples. Previous studies have established the ecological distribution and enzymatic activity of PR, but its role in powering cells and participation in ocean energy fluxes remains unclear. Here, we show that when cellular respiration is inhibited by depleting oxygen or by the respiratory poison azide, Escherichia coli cells expressing PR become light-powered. Illumination of these cells with light coinciding with PR's absorption spectrum creates a proton motive force (pmf) that turns the flagellar motor, yielding cells that swim when illuminated with green light. By measuring the pmf of individual illuminated cells, we quantify the coupling between light-driven and respiratory proton currents, estimate the Michaelis-Menten constant (Km) of PR (10(3) photons per second/nm2), and show that light-driven pumping by PR can fully replace respiration as a cellular energy source in some environmental conditions. Moreover, sunlight-illuminated PR+ cells are less sensitive to azide than PR- cells, consistent with PR+ cells possessing an alternative means of maintaining cellular pmf and, thus, viability. Proteorhodopsin allows Escherichia coli cells to withstand environmental respiration challenges by harvesting light energy.
Jessica M Walter; Derek Greenfield; Carlos Bustamante; Jan Liphardt
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2007-02-02
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  104     ISSN:  0027-8424     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2007 Feb 
Date Detail:
Created Date:  2007-02-14     Completed Date:  2007-05-17     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2408-12     Citation Subset:  IM    
Department of Physics, University of California, Berkeley, CA 94720, USA.
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MeSH Terms
Azides / pharmacology
Energy Metabolism
Escherichia coli / metabolism*,  physiology
Oceans and Seas
Proton Pumps
Rhodopsin / physiology*
Reg. No./Substance:
0/Azides; 0/Proton Pumps; 0/proteorhodopsin; 9009-81-8/Rhodopsin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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