Cloning and sequence analysis of linear plasmid telomeres of the bacterium Borrelia burgdorferi

Summary Borrelia burgdorferi, the Lyme disease agent, has double-stranded linear plasmids with covalently closed ends. DNA at the ends, or telomeres, of two linear plasmids of B. burgdorferi strain B31 was examined. Telomeric sequences from both ends of a 16kb linear plasmid and from one end of a 49kb linear plasmid were cloned and sequenced. An 18bp AT-rich inverted repeat was found at each end of the 16kb linear plasmid. The sequences of the two ends of this plasmid were different beyond these short inverted terminal repeats. The cloned end of the 49kb linear plasmid had sequence identity with one end of the 16kb linear plasmid. The end sequence common to both plasmids contained a series of phased, short direct repeats and a 52bp palindrome adjacent to a highly AT-rich region. These findings indicate that Borrelialinear plasmid telomeres have structural features different from those of other known replicons.