Heterogeneity of nucleotide sequences of 16S ribosomal RNA genes from the Desulfotomaculum kuznetsovii type strain]

Two copies of the 16S rRNA gene, rrnA and rrnB, of the type strain 17T of the thermophilic sulfate-reducing bacterium Desulfotomaculum kuznetsovii were cloned and completely sequenced. The comparison of the determined sequences revealed considerable heterogeneity (8.3%) of the two genes, rrnA and rrnB. The main differences were associated with superlong inserts located at the variable 5'- and 3'-terminal regions of the 16S rRNA genes. Comparative analysis that involved analogous genes from the phylogenetically closest representatives of the genus Desulfotomaculum showed that disregard of the heterogeneity of the two gene copies distorts the position of the bacterium studied in the phylogenetic tree.