BLAZING TOWARDS THE NEXT MILLENNIUM: LUCIFERASE FUSIONS TO IDENTIFY GENES RESPONSIVE TO ENVIRONMENTAL STRESS D. C. ALEXANDER 1 , M. A. COSTANZO 2 , J. GUZZO 2 , J. CAI 3 , N. CHAROENSRI 1 , C. DIORIO 1 , and M. S. DUBOW 1* 1 Department of Microbiology and Immunology, McGill University, 3775 University Street, Montreal, Quebec, Canada, H3A 2B4, 2 Current address: Department of Medical Genetics and Microbiology, University of Toronto, King's College Circle, Toronto, Ontario, Canada, M5S 1A8, 3 Current address: Department of Biochemistry, McGill University, 3655 Drummond Street, Montreal, Quebec, Canada, H3G 1Y6 * To whom correspondence should be addressed: Phone: 514 398 3926; Fax: 514 398 7052; e-mail: msdubow@microimm.mcgill.ca Abstract. Contamination of the environment by toxic compounds is a problem of global concern and in addressing this problem, it is necessary to identify the mechanisms by which specific agents exert their toxic effects, and develop effective, inexpensive strategies for detecting compounds in their biologically active and available form. We have used reporter gene fusion technology to identify genes, in the genetically well-characterized bacterium Escherichia coli, whose expression is affected by specific environmental toxins. As an added benefit of our approach, we have elaborated methods to use these gene fusion clones as biosensors to detect specific toxic agents, such as arsenic oxyanions. Arsenic is an abundant and useful element which is also an environmental toxin that can pose severe risks to health. Arsenic toxicity varies with oxidation state, organometallic form, and bioavailability. The Escherichia coli arsB fusion strains respond specifically to arsenic in its toxic, oxyanionic form, and can detect bioavailable amounts of these oxyanions in contaminated water samples. Combinations of different biosensor clones and assay automation will augment the use of luminescent biosensors for the detection of specific toxic agents in the environment. Keywords: arsenic, biomonitoring, biosensors, environmental genetics, Escherichia coli luciferase 1. Introduction Environmental contamination of water, air, and soil is a problem of global concern. Every year, vast quantities of natural and synthetic compounds are introduced into the environment. Contamination from both natural and anthropogenic sources is associated with extensive environmental damage and can affect the health of all living organisms. Both acute insults and long term chronic exposure can have detrimental effects, but the mechanisms by which many compounds exert their deleterious effects is not yet clear. However, in response to a toxic insult, an organism may reorganize its physiology, involving changes in gene expression. Water, Air, and Soil Pollution 123: 81–94, 2000. c 2000 Kluwer Academic Publishers. Printed in the Netherlands.