A novel, N₂-fixing cyanobacterium present and active in the global oceans

Abstract

Marine N2-fixing cyanobacteria, including the unicellular genusCrocosphaera, are considered keystone species in marine food webs.Crocosphaeraare globally distributed and provide new sources of nitrogen (N) and carbon (C), which fuel oligotrophic microbial communities and upper trophic levels. Despite their ecosystem importance, only one species,Crocosphaera watsonii, has ever been identified and characterized as widespread in the oligotrophic oceans. Herein, we present a novel species, candidatusCrocosphaera waterburyi(C. waterburyihereafter), enriched from the North Pacific Ocean, activein situ, and globally distributed in environmental datasets.C. waterburyiis morphologically, phylogenetically, and physiologically distinct fromC. watsonii; therefore, description of this novel species provides a new window into previously uncharacterized diversity and ecology of unicellular N2-fixing cyanobacterial taxa and further highlights their importance in the global N cycle.

Crocosphaera watsonii – A widespread nitrogen‐fixing unicellular marine cyanobacterium

“…CCY0110), and other species still waiting to be described (Figure 2b). Recently, a novel Crocosphaera species, Crocosphaera waterburyi, has been proposed based on metagenomic analysis from the North Pacific Ocean (Cleveland et al, 2023), and so the genus continues to expand. Furthermore, a morphologically and ecologically convergent group of diazotrophic Crocosphaera-like isolates has formed a separate genus-level lineage described as Zehria (Mareš et al, 2019).…”