Chloramphenicol acetyltransferase as a selection marker for chlamydial transformation
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Updated: May 7, 2026
Live-Cell Forward Genetic Approach to Identify and Isolate Developmental Mutants in Chlamydia trachomatis
Published on: June 10, 2020
Shuang Xu1, Lauren Battaglia, Xiaofeng Bao
1Department of Pharmacology, Rutgers University Robert Wood Johnson Medical School, Piscataway, NJ, USA. huizhou.fan@rutgers.edu.
Background:
Chlamydia is a common bacterial pathogen responsible for many diseases. Methods for transforming this important organism using a β-lactamase as a selection marker have been developed very recently. However, the National Institutes of Health Guidelines for Research Involving Recombinant DNA Molecules do not permit transformation experiments with β-lactamase gene-containing vectors for certain human chlamydial pathogens. Therefore, a different selection marker is urgently needed for transformation of those chlamydiae.
Results:
After transformation of plasmid-free Chlamydia trachomatis with pGFP:SW2, which carries a β-lactamase and a chloramphenicol acetyltransferase gene fused to a green fluorescence protein gene, transformants were obtained by selection with either ampicillin or chloramphenicol. Stable chloramphenicol-resistant, but ampicillin-sensitive, transformants were obtained using a pGFP:SW2 derivative without the β-lactamase. All transformants expressed green fluorescence protein and had glycogen synthesis activity restored.
Conclusions:
Chloramphenicol resistance may be used as a selection marker for genetic experiments in Chlamydia. This eliminates the requirement for the use of β-lactamase, of which dissemination to some C. trachomatis serovars may jeopardize clinical treatment of chlamydial infections in pregnant women. Chloramphenicol acetyltransferase may also serve as a useful secondary selection marker for genetic analyses in β-lactamase-transformed chlamydial strains.
Insights
Chloramphenicol resistance offers a new selection marker for transforming Chlamydia bacteria, crucial for research and avoiding clinical treatment risks. This method bypasses the need for beta-lactamase, improving genetic studies.
Area of Science:
- Microbiology
- Bacterial Genetics
- Molecular Biology
Background:
- Chlamydia is a significant bacterial pathogen.
- Current transformation methods use beta-lactamase, which is restricted for certain human Chlamydia pathogens by NIH guidelines.
- A new selection marker is needed for Chlamydia transformation.
Purpose of the Study:
- To develop and validate an alternative selection marker for Chlamydia transformation.
- To enable genetic manipulation of Chlamydia species restricted by current guidelines.
Main Methods:
- Transformation of plasmid-free Chlamydia trachomatis with a modified pGFP:SW2 vector.
- Selection of transformants using chloramphenicol resistance.
- Analysis of transformant characteristics, including gene expression and functional activity.
Main Results:
- Stable Chlamydia transformants were obtained using chloramphenicol selection.
- Transformants lacking beta-lactamase activity were successfully generated.
- All transformants expressed green fluorescence protein and restored glycogen synthesis activity.
Conclusions:
- Chloramphenicol resistance is a viable selection marker for Chlamydia genetic experiments.
- This approach circumvents the limitations associated with beta-lactamase markers.
- Chloramphenicol acetyltransferase can serve as a secondary marker in Chlamydia genetic analyses.
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