Goal

The goal of this element is to determine the potential for natural microbial communities to immobilize radionuclides and metals. In particular, research focuses on: 1) understanding the structure and function of microbial communities in the subsurface at DOE sites contaminated with metals and radionuclides; and 2) identifying and optimizing the in situ growth of microorganisms that transform radionuclides and metals. This research will enhance our ability to predict the effectiveness of intrinsic bioremediation and to optimize microbial communities for in situ immobilization of these contaminants.

R&D Challenges

Diverse microbial communities can be found in subsurface environments. These communities represent an untapped catalytic potential for transformation of radionuclides and metals. Most of these microbes, however, are as yet uncultured using current methods. One challenge is to use modern molecular methods to characterize these communities without the need for culturing individual organisms. In particular, scientists need to determine if sufficient genotypic and/or phenotypic potential exists to support natural attenuation or biostimulation. A second challenge is to optimize the community structure and activity for immobilization of radionuclides and metals, and to determine the long-term stability of such communities. Knowledge of microbial community structure and function may allow the stimulation and control of subsurface communities capable of immobilizing radionuclides and metals.

R&D Initiatives: Current Status

Researchers in this element are developing and applying molecular and biochemical methods to characterize the structure, activity, distribution, abundance, and diversity of microbial communities at contaminated DOE sites. They are determining ways to identify and quantify key bioremediative populations within these communities (see Figure 4). For example, specific gene probes are being developed to identify populations of radionuclide- and metal-reducing microbes.

R&D Initiative: 3 Year Targets

The role of consortial interactions will be determined in contaminated subsurface environments and comparable uncontaminated sites at the FRC and at other DOE-relevant sites. Competition among microorganisms for substrate and terminal electron acceptors, including metals and radionuclides, will be studied. The role of environmental factors (such as pH and interfacial chemistry) in regulating community structure and function will be examined. In addition, the potential importance of gene transfer at the level of microbial communities at contaminated subsurface sites will be examined to determine whether genes that transform metals and radionuclides or that protect cells from these contaminants can spread among bacteria in situ.

R&D Initiatives: 7-10 Year Targets

Growth and metabolism of key populations (such as metal reducers) will be optimized within natural microbial communities to enhance bioremediation of radionuclides and metals. Research will focus on controlling the stability (structure/function) of bioremediative communities for long-term site stewardship.