Measuring gene expression with light.

Light is produced by recombinant Escherichia coli that contain lux genes cloned from the marine bacterium Vibrio fischeri. The bioluminescence phenotype requires genes for regulatory and biochemical functions, the latter encoded by five lux genes contained in a single operon. These lux genes were disconnected from their native promoter and inserted into the transposon mini-Mu. The resulting transposon, mini-Mulux, could induce mutations by insertional inactivation of a target gene, and the lux DNA was oriented to align target gene transcription with that of the lux genes. Genes in Escherichia coli and Vibrio parahaemolyticus were mutagenized, and mutants containing transposon-generated lux gene fusions produced light as a function of target gene transcription. Light production offers a simple, sensitive, in vivo indicator of gene expression.