Microbial Geoscience

Eric Roden sampling clay-rich subsoils at Shoveler's Sink.

Microorganisms play a crucial role in geochemical processes in virtually all surface and subsurface environments on Earth. Geomicrobiology integrates microbiology with geoscience in order to understand the pathways, rates, and mineralogical transformations associated with microbial processes in geological systems, including near-surface environments impacted by human activity. Faculty in the Geomicrobiology group examine microbial activities and associated biogeochemical phenomena from a variety of perspectives.

Current research in Eric Roden’s program includes studies of the rates of and controls on microbial metabolism in sedimentary environments; the production and destruction of minerals coupled to microbial redox metabolism (specifically in relation to the mobility and fate of trace and contaminant metals); and the physiological ecology of anaerobic respiratory and lithotrophic microorganism. Experimental (bench-scale reactor) studies are conducted with pure cultures, enrichment cultures, and whole sediment microbial communities. Field studies examine the distribution of chemical elements, microbial process rates, and microbial community structure in surface and shallow subsurface sediments. A wide variety of wet-chemical, radiotracer, microscopic, spectroscopic, and molecular biological techniques are employed.

Current research in Huifang Xu’s program includes studies of microbially-induced redox reactions of Fe(III) oxides and other Fe-bearing minerals, the role of microbes in mineral formation and enrichment of trace metals, formation of mineral biosignatures of microbial life, and the effects of bioorganics on mineral shape, texture and growth kinetics. Minerals with unique shape and texture can be used as biosignatures of possible microbial activities.

Current research in Nita Sahai’s program includes studies of toxic arsenic remediation by coprecipitation of phosphate and oxyhydroxide phases; biomimetic nanosilica synthesis by the catalytic action of amine functional groups that mimic enzymes in diatoms and sponges; formation/disruption of cell-membrane phospholipid bilayers at oxide surfaces; and understanding the role of specific proteins in nucleating hydroxyapatite. A combination of experimental and modeling techniques are used, including aqueous analytical methods (e.g. ICP-AES, UV-VIS, AA), calorimetry, Infra-Red, Raman and NMR spectroscopy, Atomic Force Microscopy, Electron Microprobe and High-Resolution Transmission Electron Microscopy, quantum chemical molecular orbital calculations, molecular mechanics and molecular dynamics simulations. Professor Sahai’s program includes active collaborations with faculty in the Department of Geoscience, Chemistry, Soil Science, Biochemistry, and the Environmental Chemistry and Technology Program (ECT) at University of Wisconsin. Professor Sahai has appointments in Geoscience, and affiliate appointments in Chemistry and ECT.