J.L. Botsford1,2, T. Hillaker1, B. Robertson1, M. Gonzales1, M. Benavidez1, B. Jones1, R. Baker1, W. Steen1, F. Pacheco1, V. Homer3, O. Lucero4, M. Matthews4, and V. Koehler5, 1Department of Biology, Box 3AF, New Mexico State University, Las Cruces, NM, 88003, 2Phone: 505-646-3726, FAX: 505-646-5665, E-mail: jbotsfor@nmsu.edu; 3Fort Stanton, New Mexico; 4Gadsden High School and Las Cruces High School; and 5DVM

ABSTRACT A simple test for toxic chemicals has been developed. Rhizobium meliloti is combined with the toxic chemical. A tetrazolium dye, MTT (3-[4,5-Dimethylthiazol-2-yl]2,5-diphenyl-tetrazolium bromide) is added. The bacterium reduces this dye, causing the optical absorbance to increase dramatically. The increase can be determined with a simple spectrophotometer. Toxic chemicals and minerals inhibit the reduction of the dye. Presumably the dye serves as a terminal electron acceptor for electron transport. Toxic substances presumably damage the electron transport system. The results compare favorably with published results of tests using the Microtox(tm) assay and with the Polytox(tm) assay. This assay is simpler and requires no specialized equipment. It should be possible to use this assay in a third world situation.

KEYWORDS: toxic chemicals, assay, student involvement, bioremediation

This paper is from the Proceedings of the HSRC/WERC Joint Conference on the Environment, May 1996, published in hard copy and on the Web by the Great Plains/Rocky Mountain Hazardous Substance Research Center.

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