Discovery of nondiazotrophic <i>Trichodesmium</i> species abundant and widespread in the open ocean
Tom O. Delmont
Abstract
Significance Past studies have depicted Trichodesmium as a diazotrophic genus. This genus contributes significantly to nitrogen fixation in ocean surface waters under the form of large filaments and colonies. As a result of this unusual lifestyle, Trichodesmium is not abundant in the bacterial cellular size fraction most microbial ecologists have focused on with metagenomics thus far, and not a single environmental genome was recovered. Using large cellular size fractions of Tara Oceans, we have recovered environmental genomes of Trichodesmium and revealed a fundamental aspect of this genus: the existence of species that lost the ability to fix nitrogen (along with other critical functional traits associated with nitrogen fixation) yet are abundant and widespread on the surface of the oceans.