Based on the effects of cadmium and copper on KIHIS4 transcription when expressed in either Kluyverontyces lactis or Saccharoinyces cerevisiae, a yeast biosensor is presented. It consists of a lacZ fused to a KIHIS4 447 bp long promoter expressed in K. lactis, and as control, a second fusion with a shorter promoter not regulated by metals. This eukaryotic system can be used to detect cadmium and copper concentrations of 0.3-3 mM (or higher) within minutes using X-GAL filter assay and other variants of beta-galactosidase assays developed in multititer wells. (c) 2006 Elsevier Inc. All rights reserved.