Abstract Shewanella oneidensisMR‐1 is a promising chassis organism for microbial electrosynthesis because it has a well‐defined biochemical pathway (the Mtr pathway) that can connect extracellular electrodes to respiratory electron carriers inside the cell. We previously found that the Mtr pathway can be used to transfer electrons from a cathode to intracellular electron carriers and drive reduction reactions. In this work, we hypothesized that native NADH dehydrogenases form an essential link between the Mtr pathway and NADH in the cytoplasm. To test this hypothesis, we compared the ability of various mutant strains to accept electrons from a cathode and transfer them to an NADH‐dependent reaction in the cytoplasm, reduction of acetoin to 2,3‐butanediol. We found that deletion of genes encoding NADH dehydrogenases from the genome blocked electron transfer from a cathode to NADH in the cytoplasm, preventing the conversion of acetoin to 2,3‐butanediol. However, electron transfer to fumarate was not blocked by the gene deletions, indicating that NADH dehydrogenase deletion specifically impacted NADH generation and did not cause a general defect in extracellular electron transfer. Proton motive force (PMF) is linked to the function of the NADH dehydrogenases. We added a protonophore to collapse PMF and observed that it blocked inward electron transfer to acetoin but not fumarate. Together these results indicate a link between the Mtr pathway and intracellular NADH. Future work to optimize microbial electrosynthesis inS. oneidensisMR‐1 should focus on optimizing flux through NADH dehydrogenases.
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Shewanella oneidensis as a living electrode for controlled radical polymerization
Significance Metabolic engineering benefits from the tunable and tightly controlled transformations afforded by biological systems. However, these reactions have generally been limited to naturally occurring pathways and products. In this work, we coopt metabolic electron transfer fromShewanella oneidensisto control the activity of an exogenous metal catalyst in an abiotic reaction scheme: atom-transfer radical polymerization. In the presence ofS. oneidensis, polymerizations exhibited well-defined kinetics and yielded polymers with controlled molecular weights and low polydispersities. Additionally, polymerization activity was dependent on electroactive metabolism and specific electron transport proteins, both of which provide handles to control material synthesis. This work serves as a proof-of-principle toward expanding the scope of reactions available to metabolic engineers to include previously discovered transition-metal–catalyzed reactions.
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- Award ID(s):
- 1720595
- PAR ID:
- 10476170
- Publisher / Repository:
- Proceedings of the National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 115
- Issue:
- 18
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- 4559 to 4564
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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