Differentiation of Lactobacillus delbrueckii subspecies by ribotyping and amplified ribosomal DNA restriction analysis (ARDRA)

Aims: To differentiate the subspecies of Lactobacillus delbrueckii, subsp, delbrueckii, subsp, lactis and subsp, bulgaricus. Methods and Results: Amplified ribosomal DNA restriction analysis (ARDRA) and ribotyping were applied to over 30 strains. Both methods analyse the ribosomal genes which carry useful information about the evolutionary and taxonomic relationship among bacteria. The methods proved to be reliable and highly reproducible. ARDRA was applied to 16S rDNA, 23S rDNA and the IGS region, thus covering the whole rrn operon with eight restriction enzymes. Only EcoRI differentiated Lact. delbrueckii subsp, bulgaricus from Lact. delbrueckii subsp, delbrueckii/Lact. delbrueckii subsp. lactis, which confirmed the finding of other authors. Ribotyping with different enzymes under precisely optimized conditions revealed a high level of strain polymorphism. Only ribotyping with EcoRI allowed differentiation of the three subspecies on the basis of typical hybridization patterns. Conclusions: The successful differentiation of the three subspecies of Lact, delbrueckii by EcoRI ribotyping offers a new possibility for precise identification and differentiation of strains and new isolates. Significance and Impact of the Study: Both methods could be used for differentiation of Lact. delbrueckii subspecies.