Nitrogen is essential for all organisms on Earth, but only some bacteria and archaea can fix nitrogen.
Previous studies hypothesized that nitrogen fixation first evolved in archaea and was later transferred to bacteria. However,
analyzing >30,000 prokaryotic genomes and constructing multiple large phylogenies of nitrogen-fixing proteins,
we rejected this hypothesis and proposed the bacteria-first hypothesis,
postulating that nitrogen fixation first evolved in bacteria and was later transferred to archaea.
Published in Molecular Biology and Evolution.