Two whole-cell bioluminescent reporters were constructed by fusing the reporter genes luxAB with the Co(2+) and Zn(2+) inducible coaT promoter or the Ni(2+)-inducible nrsBACD promoter, respectively, in the genome of Synechocystis sp. PCC 6803. The obtained reporters, designated coaLux and nrsLux, respectively, responded quantitatively to metal ions. After 3 h incubation at 40 micromol m(-2) s(-1) visible light, the detection range of coaLux was 0.3-6 microM for Co(2+) and 1-3 microM for Zn(2+). Incubation in darkness increased the detection range by about four times. The nrsLux reporter was specific to Ni(2+), with a detection range of 0.2-6 microM. However, its activity was inhibited by Zn(2+) with a half maximal inhibitory concentration c. 6 microM, and totally inhibited by darkness. This is the first whole-cell Ni(2+)-specific reporter with a clear dose-signal relationship. In a soil-like mixture of different chemical and oil industry wastes, the coaLux reporter strain detected about 90% of the zinc content of the sample. This study demonstrates the potential for development of a rapid, simple and economical field assay for nickel, cobalt and zinc detection using the coaLux and nrsLux reporters.