Microscopic investigations of physiology and respiration in electrode oxidizing microorganisms

Abstract

By Edmund Leach, Biological Sciences

Advisor: Annette Rowe

Presentation ID: AM_ATRIUM11

Abstract: The ability of organisms to utilize reduced electrons from an electrode for respiration and biosynthesis has been investigated. However, the mechanistic and bioenergetic understanding of direct electron uptake is limited. Using microscopic techniques with electrochemical conditions probing for electron uptake, we sought to investigate conditions that support respiration and NADH production in an electrode oxidizing model system(s). The Alphaproteobacteria, Thioclava electrotropha and Gamaproteobacteria, Idomarina loihiensis were both isolated from a marine sediment using electrodes. These organisms also grow heterotrophically, making them a potential ideal model system. To investigate the metabolic consequences of electron uptake, we propose to utilize microscopic techniques that relate cellular electrochemical gradient (Nernstian voltage indicator, Tht) and NADH concentration (NADH-binding protein Peredox). To establish the validity of fluorescent markers for biosynthetic capacity and respiration, T. electrotropha and I. loihiensis were studied under different growth conditions where the concentration of acetate and/or the presence of oxygen was used to modulate energetic state. It was confirmed under the microscope that certain concentrations of acetate affect the NADH concentration of I. loihiensis. Also that the electrochemical gradient of T. electrotropha is proven to be affected by different acetate concentrations and oxygen states. Given preliminary results grounding truth in the utility of these fluorescent markers, electron uptake in both T. electrotropha and I. loihiensis can be investigated under various poised electrochemical conditions. This study will help in understanding the bioenergetic consequences of electron uptake in microorganisms and potentially the link between respiration and biosynthesis in electrode oxidizing organisms.