Complete sequence analysis of two cryptic plasmids from Bifidobacterium kashiwanohense JCM 15439 (type strain) isolated from healthy infant feces

Abstract Bifidobacterial plasmids reported so far are derived from a limited number of strains and plasmids of bifidobacterial type strains isolated from humans are unknown. We found that B ifidobacterium kashiwanohense JCM 15439 (type strain) isolated from a healthy infant contained two cryptic plasmids, designated pBBKW ‐1 and pBBKW ‐2. We determined and analyzed the complete sequences of both plasmids. pBBKW ‐1 (7716 bp) was predicted to replicate by a rolling‐circle mechanism and encode six protein‐coding genes, two of which are putative replication proteins. pBBKW ‐1 seems to be a cointegrate plasmid containing two copies of the plasmid pMG1 from B ifidobacterium longum . pBBKW ‐2 (2920 bp) was predicted to encode six protein‐coding genes and be a theta‐type replicating plasmid, which has been reported to be more stable than a rolling circle‐type replicating plasmid frequently found in bifidobacteria. Our finding will provide new insights into safe recombinant plasmid constructions for humans.