A novel high-throughput cell-based assay aimed at identifying inhibitors of DNA metabolism in bacteria.

Bacterial biosensor strains can be useful tools for the discovery and characterization of antibacterial compounds. A plasmid-based reporter vector containing a transcriptional fusion between the recA promoter and green fluorescence protein gene was introduced into an Escherichia coli Delta tolC strain to create a biosensor strain that selectively senses inhibitors of DNA metabolism via the SOS response. The strain was used to develop a high-throughput assay to identify new inhibitors of DNA metabolism. Screening of the Astra-Zeneca compound library with this strain identified known inhibitors of DNA metabolism, as well as novel chemotypes. The cellular target of one novel series was elucidated as DNA gyrase through genetic characterization of laboratory-generated resistant mutants followed by 50% inhibitory concentration measurements in a DNA gyrase activity assay. These studies validated the use of this antibiotic biosensor strain to identify novel selective inhibitors of DNA metabolism by high-throughput screening.