MOLECULAR-IDENTIFICATION AND CLUSTER-ANALYSIS OF HOMOFERMENTATIVE THERMOPHILIC LACTOBACILLI ISOLATED FROM DAIRY-PRODUCTS

Twenty-five strains of thermophilic lactobacilli isolated from yoghurt and from semihard and hard cheeses (in parallel with nine type or ref erence strains) were identified and grouped according to their genetic relatedness. Strains were identified by sugar fermentation patterns u sing the ''API 50 CHL'' galleries, by species-specific DNA probes in d ot-blot hybridization experiments, by amplification and restriction an alysis of the 16S rRNA gene (ARDRA) and by polymerase chain reaction ( PCR) using species-specific oligonucleotide primers. Strains were clas sified as Lactobacillus delbrueckii subsp. lactis and subsp. bulgaricu s, L. helveticus, and L. acidophilus. Strains which were atypical by s ugar fermentation patterns were also identified. Most of the strains c ould not be grouped using carbohydrate fermentation profiles. PCR fing erprinting was used to identify DNA profiles for the 25 lactobacilli. Experimentally obtained PCR profiles enabled discrimination of all str ains, which were grouped according to the similarities in their combin ed patterns. In general, the clustering of the strains corresponded we ll with species delineation obtained by molecular identification. The dendrogram of genetic relatedness enabled the unambiguous identificati on of most of the strains which were shown to be atypical by the sugar fermentation profile, except for a discrepancy in one L. delbrueckii subsp. lactis strain and one atypical Lactobacillus sp. strain.