Identification of Lactobacillus delbrueckii and subspecies by hybridization probes and PCR

Three methods addressing two different target sites were compared for ident ification and differentiation of the subspecies Lactobacillus delbrueckii s ubsp. bulgaricus and Lactobacillus delbrueckii subsp. lac tis/delbrueckii. A PCR method - three primer pairs that enable direct identification of the species and the two subspecies, respectively - was derived from a DNA fragm ent showing significant similarities to parts of the addAB genes of Bacillu s subtilis. In addition, two oligonucleotide probes for the two subspecies were designed from that DNA region. Further, two oligonucleotide probes tar geting the 16S rDNA were developed for subspecies differentiation by a one base-pair difference following identification of the species. Moreover, the se probes were demonstrated to be applicable for in situ hybridization expe riments. The results obtained by the different methods were in good agreeme nt.