Use of the Escherichia coli uidA gene as a reporter in Methanococcus voltae for the analysis of the regulatory function of the intergenic region between the operons encoding selenium-free hydrogenases.

The Escherichia coli beta-glucuronidase gene uidA was linked to a region of the Methanococcus voltae genome containing the putative promoter of a gene for a DNA-binding protein and introduced into the M. voltae chromosome. It was found that the enzyme was expressed in the cells in easily measurable amounts. The reporter gene was then placed under the control of the intergenic region found between two divergently transcribed gene groups encoding selenium-free hydrogenases, which are measurably transcribed only after selenium depletion. This region is supposed not only to contain the divergent promoters governing the transcription of the hydrogenase genes but also cis regulatory elements necessary for the negative transcriptional regulation in which selenium is involved. It was shown that the intergenic region functioned as a promoter region for the reporter gene in either orientation. The additional finding that beta-glucuronidase expression was dependent on selenium depletion localizes the cis regulatory elements to the intergenic region between the two hydrogenase operons.