Towards establishing a method to screen for inhibitors of essential genes in mycobacteria: evaluation of the acetamidase promoter

As a successful pathogen, Mycobacterium tuberculosis has effectively infected one-third of the world's population. Despite the existence of compound libraries developed by recent advances in combinatorial chemistry, few compounds have been screened against M. tuberculosis. The use of a regulable promoter to control the level of expression of a drug target in living organisms has been shown to be advantageous compared with targetless whole-cell-based or in vitro biochemical screening approaches towards antibiotic discovery. In this study, we demonstrate that the acetamidase promoter from Mycobacterium smegmatis responds in a dose-dependent manner to different concentrations of its inducer acetamide. Using this promoter to regulate expression of a zeocin resistance gene in M. smegmatis, we show that the test strain exhibits increased sensitivity to zeocin at a low concentration of acetamide compared with a fully resistant phenotype at high doses of the inducer. This model system has indicated the feasibility of using a regulable promoter in designing a whole-cell-based high throughput screen for specific inhibitors against potential drug targets of M. tuberculosis.