title: Light-driven carbon dioxide reduction to methane by nitrogenase in a photosynthetic bacterium.
abstract: Nitrogenase is an ATP-requiring enzyme capable of carrying out multielectron reductions of inert molecules. A purified remodeled nitrogenase containing two amino acid substitutions near the site of its FeMo cofactor was recently described as having the capacity to reduce carbon dioxide (CO2) to methane (CH4). Here, we developed the anoxygenic phototroph, Rhodopseudomonas palustris, as a biocatalyst capable of light-driven CO2 reduction to CH4 in vivo using this remodeled nitrogenase. Conversion of CO2 to CH4 by R. palustris required constitutive expression of nitrogenase, which was achieved by using a variant of the transcription factor NifA that is able to activate expression of nitrogenase under all growth conditions. Also, light was required for generation of ATP by cyclic photophosphorylation. CH4 production by R. palustris could be controlled by manipulating the distribution of electrons and energy available to nitrogenase. This work shows the feasibility of using microbes to generate hydrocarbons from CO2 in one enzymatic step using light energy.
authors.affiliation: Department of Microbiology, University of Washington, Seattle, WA 98195;
authors.forename: Kathryn R
authors.initials: KR
authors.lastname: Fixen
authors.affiliation: Department of Microbiology, University of Washington, Seattle, WA 98195;
authors.forename: Yanning
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322;
authors.forename: Derek F
authors.initials: DF
authors.lastname: Harris
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322;
authors.forename: Sudipta
authors.initials: S
authors.lastname: Shaw
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322;
authors.forename: Zhi-Yong
authors.initials: ZY
authors.lastname: Yang
authors.affiliation: Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Dean
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322;
authors.forename: Lance C
authors.initials: LC
authors.lastname: Seefeldt
authors.affiliation: Department of Microbiology, University of Washington, Seattle, WA 98195; csh5@u.washington.edu.
authors.forename: Caroline S
authors.identifier: 0000-0003-4450-5177
authors.initials: CS
authors.lastname: Harwood
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D015870:Gene Expression; D005818:Genetic Engineering / Q000379:methods; D007700:Kinetics; D008027:Light; D008697:Methane / Q000096:biosynthesis*; D008983:Molybdoferredoxin / Q000378:metabolism; D009591:Nitrogenase / Q000235:genetics* / Q000378:metabolism; D010084:Oxidation-Reduction; D010785:Photophosphorylation; D010788:Photosynthesis / Q000235:genetics*; D012241:Rhodopseudomonas / Q000201:enzymology / Q000235:genetics* / Q000528:radiation effects; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D008983:Molybdoferredoxin; C061338:NifA protein, Bacteria; D014157:Transcription Factors; D002245:Carbon Dioxide; D000255:Adenosine Triphosphate; D009591:Nitrogenase; D008697:Methane
keywords: Rhodopseudomonas; bioenergy; engineered bacterium; methane; nitrogenase