More microorganisms produce greenhouse gasses than previously thought

What is it about?

Nitrous oxide (N2O) is the third most harmful greenhouse gas and it is produced by bacteria and archaea in many different environments including the ocean, permafrost and grasslands. Agriculture is a major contributor to the production of nitrous oxide, with levels of N2O increasing with addition of nitrate based fertilizers. When they encounter nitrate, soil bacteria can convert it to nitrous oxide. In this study, we found a new class of enzymes that can produce this harmful gas and with this discovery, we now know that many more bacteria than previously thought can produce this greenhouse gas. By comparing genomic sequences from tens of thousands of microorganisms from different environments, we identified a new clade of enzymes that are related to well-known enzymes that reduce oxygen. We then verified that proposed function with experiments in the laboratory. This advance is helpful for us to understand the various sources and sinks of nitrous oxide, and we expect that in the future it will allow us to mitigate the release of nitrous oxide; for e.g. by advising farmers on how much nitrate-based fertilizer can be safely used.

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Photo by wilsan u on Unsplash

Photo by wilsan u on Unsplash

Why is it important?

Our work is an example of how we can leverage the large datasets that are generated by metagenomic sequencing of diverse environments to understand biological pathways with global biogeochemical importance. Metagenomic sequencing is a powerful tool to get a snapshot of the biology in different environments. It will become a useful tool for monitoring changes in ecosystems as climate change continues to adversely affect the world. However, it is important to combine insight gained from big data with careful experimental verification. Existing computational tools often mis-annotate protein function and in the example that we show, it took many researchers with different expertise working together with to show that there were more enzymes involved in nitrous oxide production than we had thought.