Nitrosopumilus adriaticus sp. nov. and Nitrosopumilus piranensis sp. nov., two ammonia-oxidizing archaea from the Adriatic Sea and members of the class Nitrososphaeria

Two mesophilic, neutrophilic and aerobic marine ammonia-oxidizing archaea, designated strains NF5(T) and D3C(T), were isolated from coastal surface water of the Northern Adriatic Sea. Cells were straight small rods 0.20-0.25 mu m wide and 0.49-2.00 mu m long. Strain NF5(T) possessed archaella as cell appendages. Glycerol dibiphytanyl glycerol tetraethers with zero to four cyclopentane moieties (GDGT-0 to GDGT-4) and crenarchaeol were the major core lipids. Menaquinone MK6:0 was the major respiratory quinone. Both isolates gained energy by oxidizing ammonia (NH3) to nitrite (NO2-) and used bicarbonate as a carbon source. Strain D3C(T) was able use urea as a source of ammonia for energy production and growth. Addition of hydrogen peroxide (H2O2) scavengers (catalase or alpha-keto acids) was required to sustain growth. Optimal growth occurred between 30 and 32 degrees C, pH 7.1 and 7.3 and between 34 and 37 parts per thousand salinity. The cellular metal abundance ranking of both strains was Fe>Zn>Cu>Mn>Co. The genomes of strains NF5(T) and D3C(T) have a DNA G+C content of 33.4 and 33.8 mol%, respectively. Phylogenetic analyses of 16S rRNA gene sequences revealed that both strains are affiliated with the class Nitrososphaeria, sharing similar to 85 % 16S rRNA gene sequence identity with Nitrososphaera viennensis EN76(T). The two isolates are separated by phenotypic and genotypic characteristics and are assigned to distinct species within the genus Nitrosopumilus gen. nov. according to average nucleotide identity thresholds of their closed genomes. Isolates NF5(T) (=JCM 32270(T) =NCIMB 15114(T)) and D3C(T) (=JCM 32271(T) = DSM 106147(T) =NCIMB 15115(T)) are type strains of the species Nitrosopumilus adriaticus sp. nov. and Nitrosopumilus piranensis sp. nov., respectively.