INTERSPECIFIC AND INTRASPECIFIC GENETIC-ANALYSIS OF THE GENUS SACCHAROMONOSPORA WITH 16S-RIBOSOMAL-DNA TO 23S-RIBOSOMAL-DNA (RDNA) AND 23S-RDNA TO 5S-RDNA INTERNALLY TRANSCRIBED SPACER SEQUENCES

In order to clarify interspecific relationships and to investigate the intraspecific phylogenetic structure of the genus Saccharomonospora, 16S to 23S ribosomal DNA (16S-23S) and 23S to 5S ribosomal DNA (23S-5S ) internally transcribed spacers (ITSs) were used for sequence analyse s. The 16S-23S and 23S-5S ITSs from 22 Saccharomonospora strains were amplified by PCR and directly sequenced. The average levels of nucleot ide similarity of the 16S-23S and 23S-5S ITSs for the four valid speci es were 87.6% +/- 3.9% and 83% +/- 2.2%, respectively. For the most pa rt, intraspecific sequence differences were not found in the two ITSs; the only exception was Saccharomonospora glauca K194, which differed from other S. glauca strains by 1 bp in the 23S-5S ITS. The Saccharomo nospora viridis strains had a smaller 16S-23S ITS region than the othe r strains, which may be useful for differentiating these organisms fro m other Saccharomonospora species. The characteristics of the two ITS regions make them more useful than 16S rRNA sequences as a tool for de fining and identifying Saccharomonospora strains. However, Saccharomon ospora azurea K161(T) had two types of 23S-5S ITSs; rrnB, separated by XhoI digestion, had two additional nucleotides inserted between posit ions 52 and 55. Most of the 16S-23S and 23S-5S ITS sequences of S. azu rea K161(T) and strains of ''Saccharomonospora caesia'' were identical ; the only exception was rrnB in S. azurea K161(T). The lengths and le vels of sequence divergence of the two ITSs of Saccharomonospora sp. s train K180 were different from the lengths and levels of sequence dive rgence of the ITSs of other species. These findings suggest that a tax onomic revision of the genus Saccharomonospora is necessary. Two trees based on 16S-23S and 23S-5S ITS sequences revealed distinct interspec ific relationships in the genus Saccharomonospora.