DNA restriction endonuclease cleavage patterns, DNA sequence similarity and phenotypical characteristics in some strains of Lactobacillus helveticus and Lactobacillus jugurti.

Physiological characteristics, deoxyribonucleic acid (DNA) base composition (% guanine + cytosine; + GC), DNA sequence similarity (% DNA-DNA hybridization) and DNA restriction endonuclease cleavage patterns of two strains of Lactobacillus helveticus and four strains of Lactobacillus jugurti were examined. All the strains investigated were closely related genetically, having DNA-DNA hybridization values ranging from 89-100%. Nevertheless, these strains can be differentiated from one another on the basis of the digestion of their DNA by specific restriction endonucleases, such as Bam HI, Eco RI and Hind III. The DNA of these strains shows clear, reproducible and distinct cleavage patterns. Cleavage patterns of DNA from strains L. jugurti S.35.19 and S.36.2 were found to be similar. These findings suggest that fingerprinting of DNA by restriction endonuclease cleavage might provide, in addition to the conventional methods, a useful tool for the characterization of closely related microorganisms at the strain level.