In the geomicrobiology group, research is directed toward understanding how interconnected inorganic and biologically-mediated processes shape the geochemistry and mineralogy of the Earth's surface. 

Much of our work centers on the ways in which microorganisms impact the form and distribution of metals in the environment. 

At present, we are investigating biogeochemical cycling of Fe, As, U, Zn, S, and P.  Projects in this area (acid mine drainage, soil formation, the subsurface biosphere) are described under the heading "low-temperature geochemistry and geomicrobiology", below. 

Because microbial activity often results in the formation of minerals with sizes in the few nanometer diameter range, a significant research focus in our group involves study of the nanoparticles. 

LOW-TEMPERATURE GEOCHEMISTRY AND GEOMICROBIOLOGY

These research projects involve the study of weathering reactions and their products. Weathering reactions are of special importance because they exert vital controls of the chemistry of water near the Earth's surface and result in the formation of the basic constituents of soils and sediments. Research in our group studies the role of both inorganic (mineral structure, chemistry, microstructure, solution characteristics, etc.) and organic (lichen communities, bacteria) factors in controlling reactions at mineral-mineral and mineral-solution interfaces. We also work on biomineralization (see below) 

ASTROBIOLOGY

BioMars project website (NASA NAI)

Microorganisms impact their surroundings in ways that are distinctive, compared to inorganic processes. In particular, minerals have the potential to record evidence of the current or pre-existence of life in a geologic setting.  At present, it is difficult to interpret features of minerals and mineral assemblages to provide definitive proof of biogenicity.  However, given many potential features that hold promise, and in view of the fact that the majority of material available for examination from the ancient Earth record and from Mars will consist of minerals, the task of mineralogical biosignture development assumes special importance. 

GENOMICS AND THE GEOSCIENCES

Genomics: GTL project website.

Microbes impact their environments and microbial communities are shaped by the geochemistry of their surroundings.  This connection is especially clear in the case of extremely acidophilic microorganisms that live in association with weathering metal sulfide deposits.  A subset of the microbes (bacteria and archaea of the Thermoplasmales group) generate energy for CO2 and N2 fixation and metabolic activity via oxidation of ferrrous iron.  The ferric iron byproduct promotes dissolution of metal sulfide minerals.  Other microbes coexisting with Fe-oxidizers generate energy by oxidation of sulfur compounds formed during oxidative dissolution of sulfide minerals.  Together, these processes lead to acidification of the environment.  Fe and S oxidizers, and associated heterotrophic bacteria, archaea, and eukaryotes have evolved to thrive in pH < 1 solutions enriched in toxic metal ions.  Because these extremophiles are difficult or impossible to study via conventional microbiological and genetic methods, we are pursuing questions related to survival in acid, microbial activity within communities, response to environmental change, and lateral gene transfer by analysis of the genomes of individual species and, ultimately of the entire community. 

MINERALOGY AND MATERIALS SCIENCE

We are interested in the fundamental nature of finely crystalline materials, especially those produced via biomineralization and chemical weathering reactions. Topics of current study include structural and microstructural analysis, morphology evolution, phase transformation kinetics, and the thermodynamics of nanocrystals. This work had direct importance to both Earth Science and Materials Science 

Visit our lab and meet some of our group!