Immunological relationships among transaldolases in the genus Bifidobacterium.

Antisera were prepared against electrophoretically homogeneous transaldolase (dihydroxyacetone transferase, E.C. 2.2.1.2.) of Bifidobacterium thermophilum (B. ruminale) RU326 (ATCC25866), B. cuniculi RA93 (ATCC27916) and B. 'minimum' (homology group) F392 (ATCC 27538). Crude extracts of eighty six strains previously assigned to twenty one species of the genus Bifidobacterium on the basis of deoxyribonouclelic acid (DNA) homology (DNA-DNA hybridization), were compared by double diffusion tests on Ouchterlony plates. Eight groups of identical antigenic specificity were recognized. By analysis of the spur formation, the groups of identical specificity were arranged in preliminary sequences of decreasing similarity to each of the three homologous transaldolases used as reference points. The relationships between immunological data and the genetic similarity among the species of the genus measured by means of DNA-DNA hybridization were discussed together with some relevant points of bifidal ecology.