Green fluorescent protein as a quantitative reporter of relative promoter activity in E-coli

Green fluorescent protein (GFP) has become a valuable tool for the detectio n of gene expression in prokaryotes and eukaryotes. To evaluate its potenti al for quantitation of relative promoter activity in E. coli, we have compa red GFP with the commonly used reporter gene lacZ, encoding beta-galactosid ase. We cloned a series of previously characterized synthetic E. coli promo ters into GFP and beta-galactosidase reporter vectors, Qualitative and quan titative assessments of these constructs show that (a) both reporters displ ay similar sensitivities in cells grown on solid or liquid media and (b) GF P is especially well suited for quantitation of promoter activity in cells grown on agas Thus, GFP provides a simple, rapid and sensitive tool for mea suring relative promoter activity in intact E. coli cells.