Identification of Lactobacillus delbrueckii and Subspecies by Hybridization Probes and PCR

Three methods addressing two different target sites were compared for identification and differentiation of the subspecies Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus delbrueckii subsp. lactis/delbrueckii. A PCR method — three primer pairs that enable direct identification of the species and the two subspecies, respectively — was derived from a DNA fragment showing significant similarities to parts of the addAB genes of Bacillus subtilis. In addition, two oligonucleotide probes for the two subspecies were designed from that DNA region. Further, two oligonucleotide probes targeting the 16S rDNA were developed for subspecies differentiation by a one base-pair difference following identification of the species. Moreover, these probes were demonstrated to be applicable for in situ hybridization experiments. The results obtained by the different methods were in good agreement.