Abstract

One of the major questions in subsurface biology is understanding how microrganisms in the subsurface are “making a living”. However, there is a dearth of knowledge concerning the physiology of major microbial groups that likely dominate the subsurface, including the lithotrophic or “rock-eating” microbes. This, in turn, makes one of the major research goals of C-DEBI, identifying and assessing activity in the deep subsurface biosphere, extremely difficult for these processes (i.e. not identified via “meta-omic” based studies) and in many cases these metabolisms are probably overlooked. Through my C-DEBI fellowship I was able to develop techniques for electrochemical cultivation of lithotrophic microbes to help facilitate identification and further study of microbial groups with these abilities. As part of this work I targeted cultivation of several groups of facultative lithotrophs that are phylogenetically related to organisms that are genetically tractable, and I’m currently in the process of building draft genomes for these microbes. It is my goal to use these microbes as model systems for understanding and biochemically characterizing the physiology of lithotrophs that will lead to better genetic markers to identify these physiologies in the environment. The work done through this fellowship has currently resulted in one publication in Frontiers in Microbiology on the electrochemical cultivation and isolation of facultative lithotrophs and tracking the physiology of cathode oxidizing microbes is the publication that will be submitted this summer. One of the most exciting results from this work is that the majority of microbes isolated from the one marine sediment tested, appear to have different redox potential where they catalyze the oxidation of a cathode suggesting a variety of different protein pathways used. This highlights both the unknown nature of these processes and the diversity of potential lithotrophic metabolic pathways.