Molecular identification of potentially probiotic lactobacilli

The rRNA-targeted oligonucleotide probes are useful for the identification of Lactobucillus acidophilus, L. gasseri, L. johnsonii, L. crispatus, and L . amylovorus. However, the oligonucleotide probe designed for L. helveticus hybridized with nucleic acids of type strains of L. gallinarum and L. helv eticus. Hence, the similarity among the 73 strains of lactobacilli was eval uated on the basis of their randomly amplified polymorphic DNA (RAPD) profi les derived from five single-primer reactions. These strains were grouped i nto seven clusters at a similarity level of 30%, which corresponded to six separate species of the L. acidophilus complex (L. johnsonii, L. gallinarum , L. amylovorus, L. crispatus, L. acidophilus, and L. gasseri, respectively ) and L. helveticus. For the first time, strains of L. gallinarum were char acterized by RAPD and PFGE analyses. The genome length in that species was estimated to be near 1.45 Mb with the summation of ApaI fragments, and near 1.95 Mb with the summation of SmaI fragments.