Over the last several years, my research has focused on the study of microorganisms and environmentally relevant microbial processes occuring in oxygen depleted (anaerobic) environments. Most experiments have utilized microorganisms from subsurface (aquifer) sediments but others have included bacteria from freshwater and marine sediments. These studies have focused both on ecological processes , that is, the interactions of microorganisms and their surrounding ecosystem and on the potential of these microorganisms to carry out bioremediation processes. 
The approach has taken several angles, with molecular studies, pure culture physiological and biochemical studies as well as studies with intact sediments. This breadth has allowed us to address questions ranging from very basic to very applied. Three projects are described in more detail below.
In this project, we have a considerable ongoing effort. This work will identify genes and ultimately physiological activities that are expressed under in situ conditions and are critical to function of sediment dwelling anaerobic bacteria especially as they live and grow in contaminated sediments. Our hypothesis is that sediment dwelling microorganisms have unique functions, encoded at the genetic level that are manifest only during exposure to conditions in contaminated environments. Further, these activities are missed using traditional in vitro laboratory incubations.
We are identifying genes of sulfate reducing bacteria (SRB) whose expression is necessary for the survival and activity of these organisms in contaminated environments. This involves the extrapolation of a molecular approach that has already proven successful for identifying genes expressed by pathogens only when these organisms are growing in a suitable host (in situ) and not when the organisms are in culture. Our approach takes on an ecological perspective. Which genes are expressed by sulfate reducers when they are exposed to and/or degrading a myriad of contaminants in sedimentary systems as opposed to those genes that may be expressed in laboratory cultures?
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| Figure Legend. Drawing of the microbial processes occuring within sandstones at the interface of Cretaceous sandstones and shales. |
We have begun to study the detoxification of metals by sulfate reducing microbial communities in the subsurface. Heavy metals and radionuclides are often found as contaminants in subsurface locations. They are especially prevalent at Dept. of Energy sites where work on nuclear weapons and nuclear energy took place. Sulfate reducing bacteria produce sulfide which reacts with many metals to form insoluble precipitates. During the process, metals become concentrated in precipitates and are simply no longer found in the groundwater.
We are focusing on determining optimal conditions for these processes to occur in the subsurface.
For more information about this program, contact the Department or Dr. Lee Krumholz.