PLAQUE-FORMATION BY AND PLAQUE CLONING OF CHLAMYDIA-TRACHOMATIS BIOVAR TRACHOMA

A new technique for the induction of plaque formation by Chlamydia tra chomatis biovar trachoma applicable to the titration of infectivity an d cloning of biovar trachoma was established. Three novel strains were cloned and confirmed to be free of glycogen inclusions. The lack of g lycogen accumulation correlated with the absence of a 7.5-kb plasmid, which is highly conserved in other strains of C. trachomatis. Although the growth efficiency of these plasmid-free strains was slightly lowe r than that of plasmid-positive strains, possession of the plasmid and glycogen accumulation were not essential for the survival of C. trach omatis.