Methane-eating microbes called ammonia oxidising archaea may be removing the potent greenhouse gas from soil in ways scientists have not accounted for. Methane traps 25 times more heat than CO₂, and global pledges aim to cut emissions by 30% by 2030. Currently, about 500–600 million tonnes of methane enter the atmosphere each year. Known methane consumers—methanotrophs—are thought to handle much of the removal, but the researchers have preliminary evidence that ammonia oxidising archaea, among the most abundant organisms on Earth, can also break down methane using an enzyme similar to the one in methanotrophs. This project will identify which microbes are actually consuming methane in soil, under what conditions, and whether methane consumption interferes with the archaea’s normal role in the nitrogen cycle. If the archaea prove to be significant methane sinks, climate models and soil management strategies will need updating. The work is fundamental science—it will not deliver a direct technology or policy tool—but understanding which organisms control methane fluxes is a prerequisite for predicting how soils respond to environmental change and for designing sustainable land-use practices that could quietly reduce greenhouse gas emissions at scale.
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Climate change is one of the greatest challenges facing our world. Methane is a powerful greenhouse gas with a global warming potential 25 times that of CO2. In the recent Climate Change Summit COP26 in 2021, an international pledge was made to urgently cut methane emissions by 30% by 2030. This project will study new microbes capable of consuming methane and generate fundamental scientific knowledge required to take the first steps towards contributing to this goal. Approximately 500-600 million tonnes of methane are emitted into the Earth's atmosphere every year. Methane can be removed by microbes known as methanotrophs. However, we have preliminary data indicating that other, previously unsuspected microbes known as ammonia oxidising archaea may also be able to consume methane in the environment. Ammonia oxidising archaea are among the most numerous living organisms on the planet and play a vital role in the nitrogen cycle. They are responsible for nitrogen loss from agricultural soils, environmental pollution and emission of nitrogen-containing climate-active gases. Ammonia oxidising archaea and methanotrophs both contain a similar enzyme, known as ammonia monooxygenase in archaea and particulate methane monooxygenase in methanotrophs. This is the key enzyme that methanotrophs use to break down methane. Our hypothesis is that archaea can use their ammonia monooxygenase enzyme to break down methane in the environment. Furthermore, we predict that methane will inhibit ammonia oxidation and thus influence nitrogen cycling in the environment. This is important because depending on the environmental conditions, different microbes will be more active than others and this has consequences for the extent of greenhouse gas emission and consumption, and cycling of nutrients. Our research will identify how different environmental conditions affect the contributions of different groups of microorganisms involved in methane removal from the biosphere. Using cutting-edge techniques, this project will link the activity and identity of the microbes responsible for methane consumption in soil. Our study will determine the mechanisms by which ammonia oxidising archaea and other microbes break down methane in soil. Overall, this will help towards predicting how soils respond to environmental changes and has considerable potential to contribute to sustainable management of soil ecosystems.
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