Random amplified polymorphic DNA analysis and demonstration of genetic variability among bifidobacteria isolated from rats fed with raw kidney beans

A rise in bifidobacterial numbers resembling the Escherichia coli overgrowt h phenomenon was observed in the rat small intestine in a feeding experimen t with kidney beans. Bifidobacterial colony counts increased from 7.6 x 10( 6) to 1.7 x 10(8) cfu.g(-1) of intestinal tissue in the anterior part and f rom less than 1 x 10(5) to 2.65 x 10(8) cfu.g(-1) in posterior part of the intestine. Fifteen bifidobacterial strains were purified and further analys ed. Random amplified polymorphic DNA (RAPD) assays were used to genetically differentiate bifidobacterial isolates from rat gut and compare them with type strains of 20 different species from the genus Bifidobacterium. A tota l of 80 arbitrary decamere primers were screened with 6 isolates, and 7 pri mers were chosen for the Final analysis. The amplified DNA bands were score d and analysed by the unweighted pair-group method using arithmetic average s clustering, The isolates were not identical to each other nor to the scre ened type strains. Whereas it was possible to group 12 of the isolates into 2 separate clusters, 3 strains showed no significant relatedness to any st rain. The results of the RAPD analysis indicated that there was a large deg ree of genetic variability among the bifidobacteria in the rat gut and demo nstrated the potential, applicability of such an approach in die investigat ion of microbial diversity in complex ecosystems.