The disclosure describes the effects of transcription mediated from a promoter on the transcription mediated by divergently coupled supercoiling-sensitive promoter. Transcription initiated from a promoter inhibits transcription mediated by a specific supercoiling-sensitive promoter that is divergently coupled to the promoter. A gyrase inhibitor relieves this inhibition and substantially increases the transcription mediated by the specific supercoiling-sensitive promoter that is divergently coupled to another promoter. Accordingly, the invention pertains to a method for identifying a compound as a gyrase inhibitor or not a gyrase inhibitor based on differential expression of genes under the control of divergently coupled promoters in the presence of the compound. Another embodiment of the invention provides an assay for identifying one or more compounds from a library of compounds as a gyrase inhibitor. Polynucleotides and cells containing such polynucleotides that are suitable for carrying out the methods described herein are also provided.