Physiological and genomic characterization two novel Nitrospira strains from the Argentinian Copahue geothermal system
Nitrification is an essential process within the global nitrogen cycle and also occurs under extreme conditions, such as in geothermal environments. The nitrite-oxidizing group Nitrospira represents key nitrifiers in these systems, as several species inhabit hot springs worldwide. Two novel moderately thermophilic Nitrospira enrichments, strain Vd2 and Ca. N. neuquenia E2OT, were obtained from sulfur-rich mud pools in the geothermal field Las Máquinas in the Copahue volcano area. One culture (Vd2) belongs to the N. bockiana lineage V, whereas the second enrichment (E2OT) represents the novel taxonomic lineage VIII, together with strains from the Kamchatka (Ns4a) and Garga hot springs (Ga3a). High-quality draft genomes were compared with those of the described species. The recent discovery of quorum-sensing genes outside the Nitrospira lineage II was confirmed for both Argentinian cultures. Notably, the GC contents are 60.6% (Vd2) and 69.4% (E2OT), the latter being the highest observed for Nitrospira to date.