Biosignatures & Paleobiology

An Alternative Path for the Evolution of Nitrogen Fixation

By Keith Cowing
March 10, 2012

A team of researchers from NAI’s Montana State University Team has proposed a new path in the evolution of biological nitrogen fixation on Earth. Nitrogen is one of the most important elements for life on Earth, and astrobiologists have long been interested in its role in the history and evolution of life.

Nitrogen is abundant on our planet as an atmospheric gas. However, in order for Nitrogen to be accessible for life, it must be converted into other chemical forms. A key step in the global cycling of nitrogen is biological nitrogen fixation, which is accomplished via a protein known as ‘nitrogenase.’ Three forms of nitrogenase are known – all similar, but containing slightly different metallic complexes. Previously, scientists thought the most common nitrogenase found today (which contains the element molybdenum (Mo)) appeared later in life’s evolution that the two lesser-found forms (containing vanadium (V) or iron(Fe)). The new study has revealed an evolutionary path that places Mo-dependent nitrogenase earlier than the V and Fe forms. The study is changing views of how this important biological pathway evolved through time – shedding light on the early history of life on Earth.

The study was published in the journal Frontiers in Microbiology under lead author Eric S. Boyd. The research was carried out as part of the NAI project “Evolution of Nitrogen Fixation, Photosynthesis, Hydrogen Metabolism, and Methanogenesis.”

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