Candidatus Nitrosocaldus islandicus Genome sequencing. Candidatus Nitrosocaldus islandicus

Ammonia-oxidizing archaea (AOA) within the phylum Thaumarchaeota are the only known aerobic ammonia oxidizers in geothermal environments. Although molecular data indicate the presence of phylogenetically diverse AOA from the Nitrosocaldus clade the group 1.1a Thaumarchaeota in terrestrial high-temperature habitats, few of these thaumarchaeotes have been functionally or genomically characterized. From the biofilm of an Icelandic hot spring, we have obtained a high (~85%) enrichment of a novel thaumarchaeote from the deep-branching Nitrosocaldaceae family. This AOA, which we provisionally refer to as “Candidatus Nitrosocaldus islandicus”, is an obligately thermophilic chemolithotrophic ammonia oxidizer with the potential for a mixotrophic metabolism.