Semester of Graduation

May 2021


Master of Science (MS)


Biological Sciences

Document Type



Carbon monoxide (CO) is primarily known for being a toxic gas. However, CO is used by microorganisms as an electron or carbon source in a variety of respiratory processes. Different kinds of microorganisms utilize CO aerobically and anaerobically, using two distinct CO dehydrogenases (CODHs). Aerobes oxidize CO using a molybdenum-dependent dehydrogenase (Mo-CODH), while anaerobes utilize a nickel-dependent CO dehydrogenase (Ni-CODH). Studies of the biochemistry and microbiology of aerobic and anaerobic CO oxidation are extensive, but relatively little is known about the ecology of anaerobic CO oxidation. In an effort to test new hypotheses about the ecology of anaerobic CO oxidation, a series of studies was undertaken using diverse soils and sediments that provided novel insights about the activity and biogeography of the process, its temperature sensitivity, and the diversity of microbial communities that participate in anaerobic CO uptake. CO uptake assays used low (10 ppm) CO concentrations under aerobic and anaerobic conditions, and high (25%) CO concentrations under anaerobic conditions at 25 °C and 60 °C. Anaerobic CO uptake occurred across all sites with low CO concentrations, even in recent volcanic deposits. Anaerobic CO uptake at high concentrations exhibited more variability. However, anaerobic CO uptake occurred in mesothermal and psychrothermal sites as well as in hot spring systems, suggesting that this process occurs in a wider range of environments and across a broader temperature range than previously reported. Analyses of microbial communities based on 16S rRNA gene sequences reveal distinct responses to elevated temperature, but less of response to elevated CO concentrations. However, there were enriched taxa, including known and putative Ni-dependent CO oxidizers, suggesting that anaerobic CO oxidizers may be more diverse than previously imagined.

Committee Chair

King, Gary M.