Genotyping of Streptococcus thermophilus evidenced by restriction analysis of ribosomal DNA.

Twenty strains of Streptococcus thermophilus were classified into five different types characterized by ribotyping after DNA digestion with HindIII and hybridization with cDNA from 16S-23S rDNA of Escherichia coli. Ribotyping after digestion with HaeIII and XhoI enabled the same strains to be gathered into three groups as a consequence of the reduced influence of the flanking sequences within the analysis of rRNA operons. Amplified rDNA restriction analysis clearly confirmed the discrimination of these three different ribotypes, producing evidence to suggest that subtaxa are to be recognized within this species.