Why Sequence a Methane-Oxidizing Archaeon?

Methane is a potent greenhouse gas whose atmospheric concentration has increased significantly because of anthropogenic activities and fluctuated naturally over glacial and interglacial cycles. While the importance of methane in Earth’s climate dynamics has been well established, the global processes regulating its oceanic cycling remain poorly understood. Although there are high rates of methane production in many marine sedimentary environments (including a number that have been targeted as petroleum reserves), net methane sources from the ocean to the atmosphere appear to be small. This is due in large part to a biogeochemical process known as the anaerobic oxidation of methane (AOM). Microbially mediated AOM reduces methane flux from ocean to atmosphere, stimulates subsurface microbial metabolism, and supports vigorous deep-sea chemolithotrophic communities along continental margins and mid-ocean-ridge systems.

Despite its widespread significance, the molecular mechanisms underlying AOM are not well understood, in part because the microbial groups known to be involved are difficult to access, exhibit slow in-situ growth rates, and remain uncultivated in the laboratory. In order to gain insight into the molecular mechanisms underlying carbon and energy metabolism associated with AOM, JGI will undertake the composite full genome sequence of one of the primary organisms, ANME-1, mediating AOM in diverse marine sedimentary environments. An iterative assembly that expands upon existing environmental whole-genome shotgun and fosmid data sets will allow construction of a tiling path for this organism. Combined with newly developed optical mapping techniques, this assembly will allow researchers to chart the genomic diversity of ANME-1 groups from multiple locations under varying physical and chemical conditions, including the Eel River Basin, Santa Barbara Basin, and Gulf of Mexico. This work will generate a solid comparative genomic foundation for reconstructing metabolic subsystems associated with AOM and provide an invaluable resource for systems-level investigations of uncultivated AOM communities under in-situ growth conditions. These studies will in turn enhance our mechanistic understanding of an ancient and important biogeochemical phenomenon with real-time impact on carbon sequestration and nutrient flow in marine ecosystems around the globe.

Principal Investigators: Steven J. Hallam (Univ. of British Columbia) and Edward F. DeLong (Massachusetts Inst. of Technology)