title: Enhancement of survival and electricity production in an engineered bacterium by light-driven proton pumping.
abstract: Microorganisms can use complex photosystems or light-dependent proton pumps to generate membrane potential and/or reduce electron carriers to support growth. The discovery that proteorhodopsin is a light-dependent proton pump that can be expressed readily in recombinant bacteria enables development of new strategies to probe microbial physiology and to engineer microbes with new light-driven properties. Here, we describe functional expression of proteorhodopsin and light-induced changes in membrane potential in the bacterium Shewanella oneidensis strain MR-1. We report that there were significant increases in electrical current generation during illumination of electrochemical chambers containing S. oneidensis expressing proteorhodopsin. We present evidence that an engineered strain is able to consume lactate at an increased rate when it is illuminated, which is consistent with the hypothesis that proteorhodopsin activity enhances lactate uptake by increasing the proton motive force. Our results demonstrate that there is coupling of a light-driven process to electricity generation in a nonphotosynthetic engineered bacterium. Expression of proteorhodopsin also preserved the viability of the bacterium under nutrient-limited conditions, providing evidence that fulfillment of basic energy needs of organisms may explain the widespread distribution of proteorhodopsin in marine environments.
authors.affiliation: BioTechnology Institute, University of Minnesota, 140 Gortner Laboratory, 1479 Gortner Avenue, St. Paul, MN 55108, USA.
authors.forename: Ethan T
authors.initials: ET
authors.lastname: Johnson
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Baron
authors.forename: Belén
authors.initials: B
authors.lastname: Naranjo
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Bond
authors.forename: Claudia
authors.initials: C
authors.lastname: Schmidt-Dannert
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Gralnick
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001709:Biotechnology / Q000379:methods; D002462:Cell Membrane / Q000378:metabolism; D003227:Conjugation, Genetic; D003470:Culture Media; D004560:Electricity; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005818:Genetic Engineering / Q000379:methods*; D008027:Light; D008564:Membrane Potentials / Q000502:physiology; D017494:Proton Pumps / Q000502:physiology; D012243:Rhodopsin / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D025604:Rhodopsins, Microbial; D020592:Shewanella / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D017494:Proton Pumps; D025604:Rhodopsins, Microbial; C413548:proteorhodopsin; D012243:Rhodopsin
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