Nucleotide sequence of the common plasmid ofChlamydia trachomatis serovar L2: Use of compatible deletions to generate overlapping fragments

All serotypes ofChlamydia trachomatis appear to have a 7.5kbp plasmid of a generally conserved sequence which occurs in 5–10 copies per elementary body genome equivalent. The plasmid from strain L₂/434/Bu was cloned and mapped for restriction enzyme sites. We determined the plasmid sequence with a family of overlapping deletions in the phagemid vector BSM13+, other recombinants created by cloning defined chlamydial restriction fragments into M13 sequencing vectors, and synthetic oligonucleotide primers. A 22-base-pair sequence, located near the uniqueSstI site of the plasmid sequence, is directly repeated four times. Although the function of this repeated sequence is uncertain, the 22-mer is in an area with an A.T-rich sequence and an open reading frame that resembles the regulatory elements and origins of replication found in other bacteria. The finding of repeated sequences on the multicopy plasmid ofC. trachomatis suggests that methods of oligonucleotide probing can be used to detect chlamydial DNA.Presented in part at the First Conference of the European Society forChlamydia Research, May 1988, Bologna, Italy.