Further Characterization of a Bacteriophage Recovered from an Avian Strain of Chlamydia psittaci

Department of Medical Microbiology, Medical School, University of Manchester, Oxford Road, Manchester M13 9PL, U.K. The genome of a 22 nm icosahedral phage which infects some avian Chlamydia psittaci strains recovered from domestic ducks has been characterized as a ss circular DNA molecule of about 4850 bases. The replicative form of this genome was isolated from purified chlamydial organisms. A restriction endonuclease cleavage site map of the genome was constructed from dsDNA synthesized in vitro from ss phage DNA and Eco RI fragments were then cloned into pUC9. The phage genome was detected only by Southern blot hybridization in C. psittaci which was productively infected with phage; no evidence was found for the integration of phage DNA into the chlamydial chromosome. Three viral polypeptides, of approximate M r values 75K, 30K and 16.5K were identified when phage was analysed by SDS-PAGE. This virus, which we have designated Chp1, is either an aberrant member of the Microviridae or the first member of a new bacteriophage family. Keywords: phage, Chlamydia psittaci , DNA, circular single strand Present address: Department of Veterinary Pathology, Royal School of Veterinary Studies, Edinburgh EH9 1QH, U.K. Received 14 December 1988; accepted 14 February 1989.