EVALUATION OF USING A SHORT REGION OF THE RECA GENE FOR RAPID AND SENSITIVE SPECIATION OF DOMINANT BIFIDOBACTERIA IN THE HUMAN LARGE-INTESTINE

The feasibility of intragenerically characterizing bifidobacteria by a comparison of a short region within the recA gene was tested. An simi lar to 300 bp fragment of the recA gene was PCR-amplified from six spe cies from the genus Bifidobacterium using primers directed to two univ ersally conserved regions of the recA gene. A phylogenetic analysis of the sequenced recA products compared favorably to classification base d on the 16S rRNA sequences of the species tested. To apply this rapid methodology to unknown human intestinal bifidobacteria, 46 isolates w ere randomly chosen from the feces of four subjects and initially char acterized by RFLP analysis of a PCR-amplified region of their: 16S RNA genes, From a representative of the dominant RFLP family in each of t he subjects, the recA segment was PCR-amplified, sequenced and phyloge netically analyzed. All four isolates were found to be related to one another and to B. longum and B. infantis. These results illustrate tha t the recA gene may be useful for intrageneric phylogenetic analysis a s well as for the identification of unknown fecal bifidobacteria.