A LUXAB TRANSCRIPTIONAL FUSION TO THE CRYPTIC CELF GENE OF ESCHERICHIA-COLI DISPLAYS INCREASED LUMINESCENCE IN THE PRESENCE OF NICKEL

From a library of 3000 Escherichia coli clones, each containing a sing le, chromosomally located luxAB transcriptional gene fusion, one clone was found in which luminescence increased in the presence of 1 to 50 ppm of NiSO4. A molecular analysis revealed that the insertion occurre d within the celF gene of E. coli. This gene encodes the phospho-beta- glucosidase involved in cleavage of the sugars cellobiose, salicin and arbutin. Cloning and sequencing of DNA downstream of the celF gene re vealed three open reading frames (potentially encoding polypeptides of 9.9, 14.1 and 28.5 kDa) that could be coexpressed with the celF gene and that may underlie the observed induction of the celF gene by nicke l. A polypeptide of 26 kDa was produced when this region was placed un der the control of the P-tac promoter. Moreover, this region was found to be directly adjacent to, and transcribed in the opposite orientati on from, the katE gene of E. coli.