EAPSI:Interactive Behavior of Methane-Consuming Microbes in Marine Sediments and their Resilience to Increased Methane Levels

Klasek Scott A, Corvallis OR

Investigators

Abstract

The potent greenhouse gas methane is responsible for about 20% of anthropogenic warming. (Tens of) megatons of methane are produced annually in marine sediments, but microbes in the sediments consume most of this methane before it is released into the ocean or atmosphere. These microbes consist of clusters of bacteria and archaea coexisting in layers of sediment where methane mixes with sulfate. Several studies have focused on characterizing the metabolism of this microbial partnership and measuring methane consumption rates, but the mechanisms by which the cells find each other, disperse, and respond to environmental changes, such as increases in methane released from subseafloor reserves, have not been characterized. Quantifying the relationships between methane concentration, cell activity, and cell density will improve carbon cycling models, allow a more accurate prediction of methane release into the ocean, and advance the understanding of a major process in the global carbon cycle. Also, identifying cellular pathways and components involved in the interactions between the two cell types will offer fundamental insight into a model archaeal-bacterial symbiosis. This research will be conducted with Drs. Fengping Wang and Ying He at Shanghai Jiao Tong University in China. Dr. Wang has enriched these cells using similar techniques and obtained their genomes to predict their nutrient cycling processes, and Dr. He?s bioinformatics expertise will help uncover new cell-cell interactions. The anaerobic oxidation of methane (AOM) by methanotrophic archaea of the ANME clades and sulfate-reducing bacteria consumes 60-90% of the methane produced in the marine subsurface, making it a crucial biogeochemical process. Long-term, high-pressure incubations of marine sediment samples in static bioreactors have been used to generate biomass and study cell growth. Incubations under different methane concentrations combined with fluorescence microscopy and comparative metagenomics and metatranscriptomics will be used to assess shifts in the composition, activity, and behavior of these microbial communities. A draft genome of an anaerobic methanotroph (ANME-2) will also be examined for chemotaxis and cell-cell signaling pathways. This NSF EAPSI research fellowship supports the research of a U.S. graduate student and is funded in collaboration with the Chinese Ministry of Science and Technology.