Treatment of Chlamydia trachomatis with a small molecule inhibitor of the Yersinia type III secretion system disrupts progression of the chlamydial developmental cycle

• Published in: Molecular microbiology Vol. 61; no. 6; pp. 1543 - 1555
• Main Authors: Wolf, K., Betts, H. J., Chellas‐Géry, B., Hower, S., Linton, C. N., Fields, K. A.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.09.2006; Blackwell Science
• Subjects: Bacterial proteins; Bacterial Proteins - analysis; Bacterial Proteins - metabolism; Bacteriology; Biological and medical sciences; Biological Transport - drug effects; Cell cycle; Cells, Cultured; Chaperonin 60 - analysis; Chaperonin 60 - metabolism; Chlamydia; Chlamydia trachomatis; Chlamydia trachomatis - drug effects; Chlamydia trachomatis - growth & development; Chlamydia trachomatis - metabolism; Coxiella burnetii; Coxiella burnetii - drug effects; Coxiella burnetii - growth & development; Fundamental and applied biological sciences. Psychology; Gene expression; Humans; Hydrazines - pharmacology; Membrane Proteins - analysis; Membrane Proteins - metabolism; Microbiology; Miscellaneous; Toxicity; Yersinia; Yersinia - drug effects; Yersinia - metabolism; Treatment; Chlamydiaceae; Microbiology; Yersinia; Chlamydiales; Bacteria; Chlamydia trachomatis; Type III secretion system; Enterobacteriaceae
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/j.1365-2958.2006.05347.x

Summary The obligate intracellular bacterium Chlamydia trachomatis possesses a biphasic developmental cycle that is manifested by differentiation of infectious, metabolically inert elementary bodies (EBs) to larger, metabolically active reticulate bodies (RBs). The cycle is completed by asynchronous differentiation of dividing RBs back to a population of dormant EBs that can initiate further rounds of infection upon lysis of the host cell. Chlamydiae express a type III secretion system (T3SS) that is presumably employed to establish and maintain the permissive intracellular niche by secretion of anti‐host proteins. We hypothesize that T3SS activity is essential for chlamydial development and pathogenesis. However, the lack of a genetic system has confounded efforts to establish any role of the T3SS. We therefore employed the small molecule Yersinia T3SS inhibitor N’‐(3,5‐dibromo‐2‐hydroxybenzylidene)‐4‐nitrobenzohydrazide, designated compound 1 (C1), to examine the interdependence of the chlamydial T3SS and development. C1 treatment inhibited C. trachomatis but not T4SS‐expressing Coxiella burnetii development in a dose‐dependent manner. Although chlamydiae remained viable and metabolically active, they failed to divide significantly and RB to EB differentiation was inhibited. These effects occurred in the absence of host cell cytotoxicity and were reversible by washing out C1. We further demonstrate that secretion of T3S substrates is perturbed in C1‐treated chlamydial cultures. We have therefore provided evidence that C1 can inhibit C. trachomatis development and T3SS activity and present a model in which progression of the C. trachomatis developmental cycle requires a fully functional T3SS.