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Title: Light-driven carbon dioxide reduction to methane by nitrogenase in a photosynthetic bacterium

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 (CO 2) to methane (CH 4). Here, we developed the anoxygenic phototroph, Rhodopseudomonas palustris, as a biocatalyst capable of light-driven CO 2 reduction to CH 4 in vivo using this remodeled nitrogenase. Conversion of CO 2 to CH 4 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. CH 4 production by R. palustris could be controlled by manipulating the distribution of electrons and energy available to nitrogenase. Furthermore, this work shows the feasibility of using microbes to generate hydrocarbons from CO 2 in one enzymatic step using light energy.
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  1. Univ. of Washington, Seattle, WA (United States)
  2. Utah State Univ., Logan, UT (United States)
  3. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
Publication Date:
Grant/Contract Number:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 113; Journal Issue: 36; Journal ID: ISSN 0027-8424
National Academy of Sciences, Washington, DC (United States)
Research Org:
Utah State Univ., Logan, UT (United States)
Sponsoring Org:
Country of Publication:
United States
60 APPLIED LIFE SCIENCES; nitrogenase; Rhodopseudomonas; bioenergy; methane; engineered bacterium
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1436487