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Front. Microbiol. | doi: 10.3389/fmicb.2019.00880

Purification and Characterization of NDH-2 Protein and Elucidating its Role in Extracellular Electron Transport and Bioelectrogenic Activity

  • 1Bioengineering and Environmental Sciences lab, CEEFF, Indian Institute of Chemical Technology (CSIR), India

In microbial electrochemical systems, transport of electrons from bacteria to an electrode is the key to its functioning. However, the role of several electron transport proteins, especially the membrane bound dehydrogenases which link cellular metabolism to EET pathway is yet to be identified. NDH-2 is a non-proton pumping NADH dehydrogenase located in the inner membrane of several bacteria like Bacillus subtilis, Escherichia coli etc. Unlike NADH dehydrogenase I, NDH-2 is not impeded by a high proton motive force thus helping in increase of metabolic flux and carbon utilization. Herein, NADH dehydrogenase II protein (NDH-2) was heterologously expressed from Bacillus subtilis into Escherichia coli BL21 (DE3) to enhance electron flux through EET pathway and understand its role in current production. We found that E. coli expressing NDH-2 has increased the electron flux through EET and has showed 3 fold increase in current (1.9 µA) production when compared to parent strain (0.4 µA). Furthermore, expression of NDH-2 also resulted in increased biofilm formation which can be corroborated with the decrease in charge transfer resistance of NDH-2 strain and increased NADH oxidation. It was also found that NDH-2 strain can reduce metal oxides (Iron citrate) at a higher rate than uninduced strain suggesting increased electron flux thorough electron transport chain due to NADH dehydrogenase II activity. Purified Ndh2 was found to be ~42 kDa and has FAD as cofactor. This work demonstrates that the primary dehydrogenases like NADH dehydrogenases can be reengineered to increase the electron flux in EET pathways which can further enhance the microbial fuel cells performance.

Keywords: NADH dehydrogenase II, Electron flux, Bioelectrochemical systems, bioelectricity, Extracellular electron transport

Received: 29 Nov 2018; Accepted: 05 Apr 2019.

Edited by:

Pascal E. Saikaly, King Abdullah University of Science and Technology, Saudi Arabia

Reviewed by:

Sunil A. Patil, Indian Institute of Science Education and Research Mohali, India
Weimin Ma, Shanghai Normal University, China  

Copyright: © 2019 Vamshi Krishna and Venkata Mohan. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Dr S Venkata Mohan, Indian Institute of Chemical Technology (CSIR), Bioengineering and Environmental Sciences lab, CEEFF, Hyderabad, Andhra Pradesh, India, vmohan_s@yahoo.com