InAlcaligenes eutrophusCH34, determinants encoding inducible resistance to chromate (chr) and to cobalt and nickel (cnr) are located adjacent to each other on plasmid pMOL28. To develop metal-sensing bacterial strains, a cloned part of plasmid pMOL28, which contains both determinants, was mutated with Tn5-lacZ. Thechr::lacZfusions were specifically induced by chromium;cnrwas induced best by Ni2+but was also induced by Co2+, Mn2+, chromate, Cu2+, Cd2+, and Zn2+. The broad-host-range IncP1 plasmid pEBZ141, which contains achr::luxfusion, was constructed.A. eutrophusAE104(pEBZ141), carrying achr::luxtranscriptional fusion, could be used as a biosensor for chromate when cultivated in glycerol as an optimal carbon source. Chromate and bichromate were the best inducers; induction by Cr3+was 10 times lower, and other ions induced only a little or not at all. Interactions among induction of thechrresistance determinant, chromate reduction, chromate accumulation, and the sulfate concentration of the growth medium were demonstrated.