CAS-Climate: Construction of a bacterium with optimized methane consumption at 10ppm for climate change mitigation

University Of Washington, Seattle WA

Investigators

Abstract

The rapid pace of climate change has created great urgency for short-term mitigation strategies and in this project, new scientific information is obtained to support strategies for removing the potent greenhouse gas methane using methane-eating bacteria. Success in this project lays the foundation for developing greenhouse gas mitigation technology that if deployed at scale, could slow global warming by 2050.This technology will buy time for the development and launch of CO2–focused interventions while keeping at bay some of the most devastating near-term impacts of a warming planet. This concept is brought to educational activities, to increase understanding of how such approaches can help the planet, and undergraduates also obtain hands-on learning in the laboratory as part of this project. Current proposed methane mitigation strategies are mainly focused on reducing emissions, and these are important goals. However, it has been argued that emission strategies must be augmented by atmospheric methane capture to slow global warming by 2050. Removing methane from the atmosphere is extremely challenging due to the low concentration (1.89 ppm). However, hundreds of thousands of emission sites exist in which the overlying methane is in the 10-100 ppm range, and these present opportunities for methane capture from air using bacteria that consume methane (methanotrophs). Naturally occurring methanotrophs that utilize methane at these levels have methane consumption rates that are much too slow to be practical. However, a methanotroph has been identified in the investigator's culture collection that grows at 500 ppm significantly better than other strains in the literature. In this project, specific traits are tested to determine whether they are involved in growth at low methane, including the affinity of the methane oxidation system, the starvation response regulatory gene rpoS, and key branchpoints in the metabolic network. Strains showing enhanced growth at low methane are characterized for growth, methane oxidation, transcripts, and fluxes at low methane, to understand how these changes affect growth parameters and the metabolic network compared to the wild type. Selection is carried out for strains with enhanced growth at 100 ppm methane, using adaptive laboratory evolution approaches, and any new traits that are identified are characterized. Methanotrophs capable of faster growth at 100 ppm and lower can be used in the future for new technology to remove methane from air. 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.