Tracking Electron Uptake from a Cathode into Shewanella Cells: Implications for Energy Acquisition from...

Area of Science:

• Microbial physiology
• Electrochemical biology
• Environmental microbiology

Background:

• Shewanella oneidensis MR-1 is known for extracellular electron transfer to anodes.
• The reverse process, electron flow from cathodes, is less understood.
• This reverse process has environmental and technological implications.

Purpose of the Study:

• To investigate Shewanella oneidensis MR-1's ability to utilize cathodic electrons.
• To understand the physiological mechanisms of cathode respiration.
• To explore the implications for microbial energy acquisition and survival.

Main Methods:

• Utilizing Shewanella oneidensis MR-1 with oxygen as the terminal electron acceptor.
• Employing electron transport chain inhibitors to study proton gradient generation.
• Measuring cellular ATP levels and redox potential (NADH/FMNH2).
• Assessing electron uptake in various mutant strains.

Main Results:

• Cathodic electrons enter the Shewanella oneidensis MR-1 electron transport chain.
• Cathode oxidation generates a proton gradient and increases cellular ATP.
• Reverse electron flow mediated by complex I generates NADH/FMNH2.
• Mutant strains showed decreased cathodic electron uptake.
• Cathode oxidation reduced cellular decay rate, indicating energy acquisition.

Conclusions:

• Shewanella oneidensis MR-1 can acquire cellular energy via cathode oxidation coupled to oxygen reduction.
• This process generates a proton gradient and increases cellular redox potential.
• Cathode respiration provides a mechanism for microbial survival in energy-limited environments.
• Findings have implications for understanding microbial persistence and bioelectrochemical systems.