A unifying theme in our work is the search for understanding of the nature and consequences of interactions between microorganisms and minerals.
Our work takes advantage of state-of-the-art methods to study of minerals as wells as new molecular, biological (genomics, gene expression), and computational techniques. Because we integrate these approaches, we describe our approach as 'molecular geomicrobiolgy'.
Our work incorporates both field and laboratory investigations. The field sites are important because they are the source of inorganic and biological materials and they provide critical constraints for our experiments. The field studies allow us to extend our understanding of geomicrobiological processes that affect the environment from molecular scales to those of a superfund site, aquifer, or hillslope.
Acid Mine Drainage
This project is focused on understanding the geochemical and biological controls on the weathering of metal sulfide minerals (pyrite and arsenopyrite), a process that leads to the generation of acid mine drainage (AMD). The field site for our work (since 1995) is the Iron Mountain Superfund site in northern California.
Our work involves a combination of mineralogy, geochemistry, microbial community analysis (including in situ studies of microbial populations and genomics-based analyses of diversity and function), kinetic studies (biologically-mediated dissolution rate studies), and surface and solution chemistry. Our work is funded by The National Science Foundation (NSF) Chemistry Program (formerly through the Environmental Geochemistry and Biogeochemistry Program, EGB), the Department of Energy Microbial Genomics Program, and the NSF Biocomplexity Program. Genomics sequencing is allocated through the Joint Genome Institute.
Biomineralization of Fe oxides and Zn sulfide
This project explores biologically-induced precipitation and growth of Fe-hydroxides, oxyhydroxides, and oxides by microaerophilic bacteria and of ZnS (sphalerite and wurtzite) by sulfate-reducing bacteria under anoxic natural conditions. The field sites for this work at in southwestern Wisconsin and at the Richmond Field Station on San Francisco Bay.
Other research focuses on the nucleation and growth of clay mineral products of biomineralization.This work overlaps directly with our work on nanocrystalline materials
Rock Weathering and Organism - Silicate Mineral Interactions
The weathering of silicate and phosphate minerals: biological and inorganic controls.
Our work includes biotic and abiotic mineral dissolution experiments, a variety of characterization studies, and field-based investigations of granite weathering profiles.
In related studies, we are investigating biomineralization of U compounds, clay minerals, and phosphates.
We are also participants in the NASA Astrobiology Institutes Program.
This work is funded by the National Science Foundation Geology and Palaeontology Program, NASA, and the US Department of Energy