A Reverse Genetic Approach for Studying sRNAs in Chlamydia trachomatis.

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Genetics

Background:

• Small RNAs (sRNAs) are crucial regulators in prokaryotes, but their function in the intracellular bacterium Chlamydia remains largely uncharacterized.
• Previous functional studies of Chlamydia sRNAs relied on heterologous systems, limiting insights into their native roles.

Purpose of the Study:

• To establish an inducible sRNA overexpression system in Chlamydia trachomatis for functional genetic studies.
• To screen Chlamydia sRNAs for their impact on the bacterial developmental cycle (RB to EB conversion).
• To identify the mRNA targets of the sRNA CtrR3 within Chlamydia.

Main Methods:

• Developed an inducible sRNA overexpression system in Chlamydia trachomatis.
• Screened 13 C. trachomatis sRNAs for effects on the developmental cycle.
• Utilized MS2 aptamer affinity purification coupled with RNA sequencing to identify mRNA targets.
• Validated target interactions using bioinformatic analysis, mutational studies, and translational fusion assays.

Main Results:

• Overexpression of four out of 13 screened sRNAs significantly reduced infectious elementary body (EB) production.
• CtrR3 overexpression blocked the conversion from reticulate bodies (RB) to EBs, while CtrR7 overexpression inhibited bacterial replication.
• Identified YtgB and CTL0389 as direct mRNA targets of CtrR3 in Chlamydia.

Conclusions:

• The developed inducible sRNA overexpression system is effective for studying sRNA function in Chlamydia trachomatis.
• This system facilitates the investigation of sRNA roles in bacterial development and pathogenesis.
• The identification of CtrR3 targets provides a foundation for understanding its regulatory mechanisms in Chlamydia.