Collaborative Research: Examination of Diverse Anaerobic Methane Oxidizing Archaea and Associated Syntrophic Relationships Using High Resolution Molecular and Isotopic Methods

The characterization of methane-consuming microorganisms and the factors that control their activity on the micro scale is important in our understanding the biogeochemical cycling of methane on a global scale. The world's oceans are one of the largest sources of methane, yet only a fraction of this greenhouse gas is released into the atmosphere because it is consumed by microorganisms in anoxic marine sediments. Cross-disciplinary investigations have recently shown that the process of anaerobic oxidation of methane (AOM) is mediated by novel uncultured Archaea, the ANME-1 and ANME-2, in syntrophic association with sulfate-reducing bacteria.

This project is studying methanotrophic Archaea (including ANME-1 and ANME-2) from methane seep environments and pure cultures of Methanosarcina acetivorans and Methanococcoides methylutens (close cultured relatives of the ANME-2) using a series of experiments combining fine scale molecular RNA-based and isotopic analyses. The objectives are aimed at identifying the microbes responsible for and understanding the process of AOM through three broad areas of research. The goals of this research are: (1) to characterize the diversity and metabolic versatility of microorganisms responsible for AOM by expanding and refining the current database on the natural carbon isotopic composition of cells in methane-rich sediments, (2) to develop constraining thermodynamic models of AOM by identifying where active cells reside in natural ANME-2/Desulfosarcina consortia, (3) to elucidate metabolic aspects of AOM by constraining intermediates of the process and by identifying possible vitamins and co-factors involved. These cross-disciplinary studies are hypothesis-driven investigations aimed at understanding the underlying mechanisms and syntrophic relationships of methane-oxidizing microbial cells and consortia through combined cell-specific molecular and isotopic analyses. This research will generate a unique high-resolution isotopic data set that will serve as a basis for modeling the thermodynamics of AOM as well as assist in defining the complex interactions between microorganisms involved in the cycling of methane. This approach is highly complementary to ongoing studies of anaerobic methane oxidation by geochemists and microbiologists and provides a unique perspective to assist in elucidating this globally important, but poorly characterized process.

The education and outreach program will expand interest in geomicrobiology at the grade school, undergraduate, and graduate level. This project will provide team-oriented graduate education in microbial geobiology, engaging undergraduates through existing programs aimed at increasing diversity in the sciences, and building on existing infrastructure aimed at K-12 teacher education. Specifically, the PIs are contributing to the annual PSU teacher's workshop by teaching a session on the important role microbes play in regulating climate on Earth. Through connections with Dr. Benita Bell from Bennett College, a historically Black women's college in Greensborough, North Carolina, the PIs are introducing underrepresented students to the field of geobiology through a workshop during Space Science Week at Bennett. At the graduate level, the project will provide educational opportunities to graduate students at Penn State and Caltech.