Conserved DNA Sequences in Chlamydial Plasmids
ANDREW HUGALL1, PETER TIMMS2, ADEEB A. GIRJES1, AND MARTIN F. LAVIN1
1Queensland Institute of Medical Research, Bramston Terrace, Herston, Brisbane 4006, Australia
2Department of Medical Laboratory Science, Queensland University of Technology, Brisbane 4000, Australia
Two 7.4-kb plasmids from Chlamydia psittaci have been cloned and characterized. These plasmids are quite distinct from the 6.2-kb C. psittaci and the C. trachomatis plasmids when compared by restriction endonuclease analysis. The plasmids show considerable cross-hybridization, with only a small region highly conserved and identified as a 4 X 22-bp tandemly repeated region. This sequence is identical in the two size categories of C. psittaci plasmids and differs from C. trachomatis plasmids by only 2 bp in the 22-bp motif. AT-rich clusters 5’ to the repeat region which are present in C. trachomatis and Escherichia coli plasmids were absent from both classes of C. psittaci plasmids. Extensive regions are less highly conserved but show a sufficient degree of cross-hybridization to suggest that the plasmids are homologous.