This work presents a novel micro-fluidic whole cell biosensor for water toxicity analysis. The biosensor presented here is based on bacterial cells that are genetically "tailored" to generate a sequence of biochemical reactions that eventually generate an electrical signal in the presence of genotoxicants. The bacterial assay was affected by toxicant contaminated water for an induction time that ranged between 30 min and 120 min. Enzymatic substrate (pAPP) was added to the assay generating the electrochemical active material (pAP) only when toxicants are sensed by the bacteria. The bacteria were integrated onto a micro-chip that was manufactured by MEMS technology and comprises various micro-chambers with volume ranging between 2.5 nl and 157 nl with electrode radius between 37.5 mu m and 300 mu m. We describe the biochip operation, its electrochemical response to calibration solutions as well as to the whole cell assays. The potential use of the whole cell biochip for toxicity detection of two different genotoxicants, nalidixic acid (NA) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), is demonstrated. We demonstrate minimal toxicant detection of 10 mu g/ml for NA using 30 min for induction and 0.31 mu M for IQ using 120 min for induction, both 3 min after the addition of the substrate material. (C) 2009 Elsevier Ltd. All rights reserved.