Toxi-Lab™ Testing Educational Kit
Acute Toxicity Test for the Classroom
Timeline: 2 to 3 Classroom Periods About the Toxi-Lab™: The Toxi-Lab™ determines environmental toxicity and can be used for a variety of toxic substances such as heavy metals, as well as organic and inorganic pollutants. The test determines the relative toxicity of different samples at varying concentrations. The Toxi-Lab™ uses a non-pathogenic, harmless, mutated strain of E. coli specifically engineered to be highly sensitive to toxic substances. In microplate wells, the bacteria are exposed to different concentrations of a test chemical for a period of time, and the chemical’s effect on the health and survival of the bacteria is measured. |
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Reaction: The Toxi-Lab™ takes advantage of E.coli’s natural ability to produce an enzyme called β-galactosidase which is used by bacteria to metabolize the food source lactose. The E.coli bacteria was exposed to stressing conditions and need to first recover, before they will actively produce β-galactosidase. The bacteria was incubated in a cocktail containing essential factors required for the recovery of the bacteria, a specific inducer of β-galactosidase, and the test chemical. This bioassay is based on the knowledge that a biologically active toxicant or chemical can interfere with the bacteria’s recovery process, diminishing β-galactosidase’s action or preventing its production, effectively slowing down or even stopping the digestion of lactose. We provide a synthetic sugar (a chromogen called X-gal) to emulate the lactose. β-galactosidase recognizes this imposter molecule as “lactose” and cleaves (hydrolyzes) the X-gal, producing a blue colour in the well with the bacteria. The amount of blue chromogen released reveals the extent to which the chemical is harmful to this living cell. |
EDUCATIONAL LAB HANDOUT
Download the Handout which includes Educator Resources, Student Handout, Preparation, and Lab Procedure |
Learning Goals (see About Us for Details): LG 1, LG 2, LG 3, LG 4, LG 7, LG 8, LG 9 Toxi-LabTM Information for the Educator |