Plasmid-mediated transformation tropism of chlamydial biovars

Abstract

Chlamydia trachomatis and C.muridarum are human and mouse pathogens, respectively, which show high conservation of gene order and content. Both species contain a common 7.5-kb plasmid that is an important virulence factor. Recently described transformation systems have been used to characterize C.trachomatis L2 plasmid gene functions; however, similar studies have not been reported for C.trachomatis ocular tropic serovar A or the mouse strain, C.muridarum. Here, we have conducted genetic experiments with C.trachomatis serovar A and C.muridarum and report the following: (1) successful transformation of C.muridarum and C.trachomatis serovar A is restricted to a shuttle vector with a C.muridarum or C.trachomatis serovar A plasmid backbone, respectively; (2) transformation of plasmid-deficient C.muridarum with the C.muridarum-based shuttle vector complement glycogen accumulation and inclusion morphology; and (3) C.muridarum plasmid-encoded Pgp4 is a regulator of chromosomal (glgA) and plasmid (pgp3) virulence genes. In summary, our findings show a previously unrecognized and unexpected role for the chlamydial plasmid in its transformation tropism and confirm the plasmids regulatory role of virulence genes in C.muridarum.