Distinct Expression of the Two NO-Forming Nitrite Reductases in Thermus antranikianii DSM 12462 Improved Environmental Adaptability.

Hot spring ecosystems are analogous to some thermal environments on the early Earth and represent ideal models to understand life forms and element cycling on the early Earth. Denitrification, an important component of biogeochemical nitrogen cycle, is highly active in hot springs. Nitrite (NO) reduction to nitric oxide (NO) is the significant and rate-limiting pathway in denitrification and is catalyzed by two types of nitrite reductases, encoded by nirS and nirK genes.

Comparative genomics analysis of Nitriliruptoria reveals the genomic differences and salt adaptation strategies.

The group Nitriliruptoria, recently classified as a separate class of phylum Actinobacteria, has five members at present, which belong to halophilic or halotolerant Actinobacteria. Here, we sequenced the genomes of Egicoccus halophilus EGI 80432 and Egibacter rhizosphaerae EGI 80759, and performed a comparative genomics approach to analyze the genomic differences and salt adaptation mechanisms in Nitriliruptoria. Phylogenetic analysis suggested that Euzebya tangerina F10 has a closer phylogenetic relationship to Euzebya rosea DSW09, while genomic analysis revealed highest genomic similarity with Nitriliruptor alkaliphilus ANL-iso2 and E.