Original Research ARTICLE
Shewanella oneidensis NADH dehydrogenase mutants exhibit an amino acid synthesis defect
- 1Michigan State University, United States
Shewanella oneidensis MR-1 is a dissimilatory metal reducing bacterium with a highly branched respiratory electron transport chain. The S. oneidensis MR-1 genome encodes four NADH dehydrogenases, any of which may be used during respiration. We previously determined that a double-knockout of two NADH dehydrogenases, Nuo and Nqr1, eliminated aerobic growth in minimal medium. However, the double-knockout strain was able to growth aerobically in rich medium. Here, we determined that amino acid supplementation rescued growth of the mutant strain in oxic minimal medium. To determine the mechanism of the growth defect, we monitored growth, metabolism, NADH/NAD+, and membrane potential in S. oneidensis MR-1 and NADH dehydrogenase knockout strains. We also used a genetically encoded redox sensing system and determined that NADH/NAD+ was higher in the mutant strain than in the wild-type. We observed that the double-knockout strain was able to metabolize D,L-lactate and N-acetylglucosamine when supplemented with tryptone, but excreted high concentrations of pyruvate and acetate. The requirement for amino acid supplementation, combined with an apparent inability of the mutant strain to oxidize pyruvate or acetate suggests that TCA cycle activity was inhibited in the mutant strain by a high NADH/NAD+.
Keywords: Shewanella, redox, Respiration, electron transport chain, NADH Dehydrogenase
Received: 21 Jun 2019;
Accepted: 04 Oct 2019.
Copyright: © 2019 Duhl and TerAvest. 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: Mx. Michaela TerAvest, Michigan State University, East Lansing, 48824, Michigan, United States, firstname.lastname@example.org