Potentially damaging reactive oxygen species (ROS) are involved in a number of pathways ranging from signal transduction to apoptosis. Cells have adapted this alteration in redox status into a complex regulatory mechanism. ROS are specifically able to induce the expression of a multitude of genes. We constructed and characterized "oxidative stress probes" consisting of promoter fusions of several ROS-induced genes and the green fluorescent protein (GFP) reporter gene. Specifically, the sodA, fumC, zwf, acnA, acrAB, and soxS genes from the SoxRS regulon and the katG and ahpC genes from OxyR regulon, which respond to the superoxide anion and hydrogen peroxide, were studied. Our results revealed not only different levels of background transcription, but different induction levels both in terms of timing and strength. These systematic studies were performed under a uniform parallel platform and have provided insight into the complicated gene regulation of the oxidative stress regulons. (C) 2005 Wiley Periodicals, Inc.