This project will investigate mechanisms by which methane-producing microorganisms can utilize an important and understudied class of compounds to produce methane. Methane, the key component of natural gas, plays an important role in global carbon cycling and atmospheric processes. Some methane-producing microbes (methanogens) have recently been shown to convert a group of compounds called quaternary amines (QAs) to methane. QAs are abundant compounds in many different environments, and methanogenesis in the human gut has been linked to the development of heart disease. Current knowledge of how methanogens can convert QAs to methane and how prevalent this process is in the environment is distinctly lacking. This gap in knowledge leads to potential inaccuracies in computer-generated models predicting the role of methanogenesis on Earth's atmosphere. This research project will address this gap in knowledge by 1) investigating the physiological mechanisms of methanogenesis via QAs and 2) identifying and quantifying the microorganisms responsible for this process in different environments. This research will also benefit students at the Miami University Hamilton, part of a community-based division of Miami University that serves students from first-generation, lower socioeconomic status, and under-represented minority groups. These students will contribute to the research project through classroom activities and undergraduate research.
Quaternary amines (QAs) are abundant natural compounds that have recently emerged as important substrates for microbes in anoxic environments, including methanogens. The breakdown of QAs has direct implications for diverse processes from global biogeochemical cycling to atherosclerosis in humans. Understanding of the mechanisms of anaerobic catabolism of QAs by methanogenic archaea, namely QA demethylation, is lacking. Early data suggest that pyrrolysine-lacking (non-pyl) methyltransferases from the COG5598 protein family are involved in QA-dependent methanogenesis along with cognate corrinoid binding proteins, but these pathways have not been elucidated. Determining the function of multiple enzymes from this family will facilitate better identification of the role of members of COG5598 in methane production. The central hypothesis of this proposal is that non-pyl COG5598 enzymes are responsible for QA demethylation and initiation of QA-dependent methanogenesis as part of a three-component corrinoid-dependent methyl transfer pathway, and that organisms encoding these pathways can be identified within the environment. In this work the investigators will: 1) identify pathways for QA-dependent methanogenesis from glycine betaine and tetramethylammonium using comparative proteomics and biochemistry techniques, and 2) determine the identities and relative abundance of predicted QA-utilizing methanogens in different environments.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
