A Mineral-reducing microbe on life support: physiology of Shewanella oneidensis MR1 on a cathode

A.K.A. Reversing the flow…

It has been known for a while that microbes can breathe electrodes—use them as a sink for electrons they acquire from the food they eat the way you and I use oxygen. The difference with these microbes is that in order to do this they have to transport electrons outside the cell (in most microbes, including our mitochondria, redox reactions are localized to the inner membrane). In many ways this processes is just an expansion of one of the things I love most about microbes: that they can eat and breathe an amazing diversity of compounds including things that seem absolutely crazy to us humans, such as rocks, toxins, and even radioactive materials. But what has fascinated me recently, is the fact that these processes are reversible . This has led me to try to figure out how or why these same organisms that give electrons to electrodes (breathe), can sometimes take up electrons from electrodes (eat). To do this I had to mix electrochemistry, biochemisty and cell physiology to figure out if and or how these microbes make a living running things in reverse. Though this has important implications for microbe electrode interactions, the bigger questions is (that is infinitely harder to answer): does this happens in the real world?

In press in mBio


Shewanella on cathodes has important implications for electrosynthesis and systems biology. My current work on this organism is tackling energetic models of reverse electron flow: how much energy do you need (i.e. proton motive force) in order to generate NADH.  Empirically we are modeling these processes by  measuring the NADH and in the cell under different respiratory rates to see if we can link these processes. This will be the ground work for then trying to perturb and then optimize  the system for getting as much electron power going to making biofuels. 

 Astrobiology, Bioremediation, Ecology in MicrobesElectromicrobiology, Environmental Microbiology, and Geomicrobiology