GENES REQUIRED FOR ASSEMBLY AND FUNCTION OF THE PROTEIN SYNTHETIC SYSTEM IN CHLAMYDIA-TRACHOMATIS ARE EXPRESSED EARLY IN ELEMENTARY TO RETICULATE BODY TRANSFORMATION

Following binding and internalization into the host cell cytoplasm, el ementary bodies (EB) of the obligate intracellular bacterium Chlamydia trachomatis undergo a developmental process resulting in production o f reticulate bodies (RE), the vegetative growth form of the organism. EB are metabolically inactive, but EB to RE transformation requires ba cterial :protein synthesis. Using HeLa cells infected with EB of C. tr achomatis serovar C, we examined the time of first appearance of trans cripts from several genes whose products are required for assembly and function of the chlamydial protein synthetic system. We monitored app earance of chlamydial RNAs using reverse transcription-polymerase chai n reaction assays targeting primary transcripts from the bacterial rRN A operons, and mRNAs encoding the glycyl tRNA synthetase and the ribos omal proteins S5 and L5. Transcripts from the proximal rRNA promoters, and those from the r-protein and tRNA synthetase genes, are detectabl e as early as 4 h after EB-host binding; transcripts from distal rRNA promoters do not appear until 6 h post-infection. Thus, expression of bacterial genes whose products are required for protein synthesis begi ns earlier in chlamydial EB to RE development than previously thought.