Requirement of GrgA forChlamydiainfectious progeny production

ABSTRACTHallmarks of the developmental cycle of the obligate intracellular pathogenic bacteriumChlamydiaare the primary differentiation of the infectious elementary body (EB) cell type into the proliferative reticulate body (RB) and the secondary differentiation of RBs back into EBs. The detailed mechanisms regulating these transitions are unclear. In this study, we developed a novel strategy termed DOPE (dependence on plasmid-mediated expression) that allows for the knockdown of essential genes inChlamydia. Importantly, we demonstrate that GrgA, aChlamydia-specific transcription factor, is essential for the secondary differentiation of RBs into EBs. Our development of a conditional GrgA-deficient chlamydiae should prove valuable for future studies examining chlamydial growth, development, and pathogenicity. Furthermore, because EB formation is absolutely required for chlamydial dissemination within infected individuals, and for chlamydial transmission to new hosts, our maturation-defective chlamydiae system may serve as an attractive attenuated vaccine methodology for the prevention of chlamydial diseases.