Time to rethink nitrification

Two groups this week report the enrichment and characterization of Nitrospira species that encode all of the enzymes necessary to catalyse complete nitrification, a phenotype referred to as 'comammox' (for complete ammonia oxidation). Until now, this two-step reaction was thought to involve two organisms in a cross-feeding interaction. Phylogenetic analyses suggests that comammox Nitrospira are present in a number of diverse environments, so these findings have the potential to fundamentally change our view of the nitrogen cycle and open a new frontier in nitrification research.