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Two novel ammonia-oxidizing bacteria, designated strains wSCUT-1 T and wSCUT-2 T , were isolated from domestic wastewater collected from a domestic sewage treatment system in Shantou city and activated sludge collected from a wastewater treatment plant in Zhaoqing city, respectively. Cells of strain wSCUT-1 T were rod-shaped, and cells of strain wSCUT-2 T were straight rod-shaped. Strain wSCUT-1 T grew at 18‒37 °C (optimum 30 °C), pH 6‒9 (optimum pH 7‒8) and in 0‒10 g l −1 NaCl. Strain wSCUT-2 T grew at 18‒37 °C (optimum 30‒37 °C), pH 6‒9 (optimum pH 7.5‒8) and in 0‒10 g l −1 NaCl. The optimum growth for both strains occurred at 10 mmol l −1 NH 4 + . The major cellular fatty acids of both strains were C 16:0 and sum feature 3 (comprising C 16:1 ω 7c and/or C 16:1 ω 6c). DNA G+C contents of wSCUT-1 T and wSCUT-2 T were 48.95 and 48.24 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene indicated that the closest relative of strain wSCUT-1 T is Nitrosomonas ureae Nm10 T , with an identity of 95.54%, while the closest relative of strain wSCUT-2 T is Nitrosomonas oligotropha Nm45 T , with an identity of 95.97%. The identity between wSCUT-1 T and wSCUT-2 T is 97.93%. Strain wSCUT-1 T showed average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values of 85.96%, 73.23% and 31.2% with wSCUT-2 T and ranged from 67.77 to 76.72%, 53.53 to 63.2% and 13.00 to 19.90% with other related strains, respectively. Based on phenotypic, genotypic and phylogenetic analyses, strains wSCUT-1 T and wSCUT-2 T are considered to represent new species of the genus Nitrosomonas , for which the names Nitrosomonas domestica sp. nov. and Nitrosomonas limosa sp. nov. are proposed, respectively. The type strains of N. domestica and N. limosa are wSCUT-1 T (=GDMCC 1.5355 T =JCM 39615 T ) and wSCUT-2 T (=GDMCC 1.5354 T =JCM 39616 T ), respectively.
Zheng et al. (Tue,) studied this question.