Chlamydia is an obligate intracellular bacterium that differentiates between two distinct forms during its developmental cycle: elementary bodies (EBs) and reticulate bodies (RBs). The EB is the small, electron dense form that mediates host cell infection. Within the cell, the EB differentiates into the RB, which is the replicative form that develops within a host membrane derived vesicle, termed an inclusion. RBs replicate within this inclusion and eventually differentiate back into EBs. Upon accumulation of EBs at the end of the developmental cycle, the host cell lyses, releasing the EBs for infection of proximal cells. The EB and RB have distinct proteomic profiles, and, given the unique functional and morphological forms, the role of proteomic turnover through protein degradation is understudied in Chlamydia. We hypothesize that the CIP protease system plays an integral role in protein turnover by targeting specific proteins from one developmental form or the other for degradation. Chlamydia contains five genes encoding five CIP genes: clpX, clpC, two clpP paralogs, and clpB. Homotypic oligomerization of the CIP proteins was determined with bacterial two-hybrid assays and native-PAGE gels. Transcriptional analysis via RT-qPCR determined these genes are expressed mid-cycle. Antibiotics that non-specifically activated the ClpPs negatively affected chlamydial development. Additionally, inducible, poly-histidine tagged inactive CIP mutants were used to determine the effect of overexpression on Chlamydia. Taken together, these data suggest that i) the CIP system of Chlamydia functions comparably to other bacteria and ii) CIP proteins are important for chlamydial growth and development
