Development of a quantitative gene expression assay for Clamydia trachomatis identified temporal expression of σ factors

Chlamydia trachomatis is an important human pathogen which possesses a unique bi-phasic developmental cycle. We used lightcycler methodology to quantitatively measure gene transcript levels in C. trachomatis strain L2. By measuring 16S rRNA transcript levels, we determined C. trachomatis L2 to have a generation time of approximately 3 h and an inclusion burst size of 200-300 particles. The three chlamydial a factor genes rpoD (sigma(66)), rpsD (sigma(28)) and rpoN (sigma(54)) exhibited different patterns of temporal expression. rpoD was central to early chlamydial development, whereas rpsD and rpoN were temporally expressed, coinciding with elementary body (EB) to reticulate body (RB) conversion and RB to EB conversion, respectively. (C) 1999 Federation of European Biochemical Societies.