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Summary In this report 16S rRNA gene sequences from seven new isolates of the genus Nitrosospira were determined, and used in a phylogenetic analysis. The homology values for these 16S rDNA sequences ranged from 97.4% to complete homology. In general, the three closest related genera of ammonia-oxidizers - Nitrosospira, Nitrosolobus and Nitrosovibrio - have 16S rDNA sequences with homology values from 96.9%, giving low resolution when the taxa are positioned in a phylogenetic tree. Thus, while these ammonia-oxidizers possess distinct morphological differences; these differences seem not to be reflected in the 16S ribosomal DNA sequences. This suggests that the morphological traits have evolved recently, and that 16S ribosomal RNA analysis alone is not sufficient to determine the evolutionary relationship between them. The results of this phylogenetic analysis confirm the previously proposed emendation of the genus classification within these bacteria. |
