Application of PCR for Selection of Gram-Positive Bacteria with High DNA G+C Content among New Isolates

A PCR condition was established to distinguish strains of Actinobacteria from both Gram-negative bacteria and Gram-positive bacteria with low G+C content of DNA by taking advantage of a stable, specific and common insertion of a 100 bp sequence in the domain III of the 23S ribosomal RNA gene of class Actinobacteria. The PCR was designed to amplify a 380 bp fragment from Actinobacteria and a 270 bp fragment from the above bacteria. PCR-based survey of known strains as well as newly isolated soil bacteria confirmed that this PCR worked well to select Actinobacteria. In the survey it was unexpectedly found that several strains provided both 270 bp and 380 bp amplified fragments (the sequences of these two fragments obtained from Agrococcus jenensis were determined), indicating the presence of at least two copies of the domain III of the 23S rDNA gene.