Our laboratory studies chemical transformations carried out by anaerobic microorganisms and the properties of those organisms. We presently have two major projects in the laboratory:
- microbiology of conversion of organic matter to methane in peat bogs and other wetlands, and
- microbial reductive dechlorination of chlorinated organic compounds. In the past we've also studied conversion of acetate to methane by thermophiles and nitrogen fixation by methanogens.
Methanogenesis in peatlands
Approximately one-third of soil organic carbon is stored in northern peatlands, and they are also a major source of methane in our atmosphere, the concentration of which has more than doubled in the past 200 years. We know little about the microorganisms involved in methanogenesis in Sphagnum moss-dominated acidic peat bogs, since none of the responsible organisms have been isolated. Our laboratory, in collaboration with that of Dr. Joseph Yavitt in the Department of Natural Resources at Cornell, received funding from the NSF Microbial Observatories Program to use microbiological, biogeochemical, and molecular biological tools to study microbes in peatlands. Our primary research site is McLean Bog about 30 km from Cornell. We have demonstrated using molecular biological tools that diverse populations of methanogens exists in McLean Bog , none of which have been cultured, until our recent studies. For more information, visit the website for our Microbial Observatories Project.
Chlorinated organic compounds are among the most pervasive and persistent groundwater pollutants. Our laboratory studied a mixed enrichment culture, developed in the laboratory of Dr. James Gossett, School of Civil and Environmental Engineering at Cornell, that reductively dechlorinated the important groundwater pollutants tetrachloroethene (PCE) and trichloroethene (TCE) to ethene, thereby detoxifying them. These studies led to the isolation of Dehalococcoides ethenogenes, an unusual organism that uses chlorinated solvents as electron acceptors for respiration in a manner analogous to how we use oxygen. Reductive dechlorination is now being used to bioremediate many PCE and TCE-contaminated sites, and Dehalococcoides spp. have been shown to play a crucial role in that process. Moreover, different Dehalococcoides strains have been shown to dechlorinate other chlorinated pollutants including PCBs, chlorobenzenes, and dioxins.
In collaboration with The Institute for Genomic Research, the genome sequence of D. ethenogenes was recently determined, which showed that it was highly evolved for reductive dechlorination, having over 17 genes predicted to encode reductive dehalogenases. Moreover the genome of Dehalococcoides strain CBDB1, which uses chlorinated benzenes, has 32 genes predicted to encode reductive dehalogenases! In an NSF-funded project we are using quantitative PCR and proteomic techniques to examine gene expression in pure and mixed cultures containing Dehalococcoides, the latter in collaboration with Dr. Ruth Richardson, School of Civil and Environmental Engineering. We are also examining the utilization of other chlorinated compounds by this fascinating microbial group.