Related structures in the plasmid profiles of Bifidobacterium longum.

The plasmid profiles of 123 strains of B. longum were examined with the Southern blot-hybridization technique to reveal the existence of related structures. B. longum is the apparently unique species among those commonly found in man, which harbours extrachromosomal elements. Seven different structures were found and their frequency and distribution given. Twelve strains were used a source of probes in the hybridization experiments.