Bacterial Phenotypes (IND-15)

Genes introduced into E.coli by plasmid-mediated transformation can confer variation in the phenotype of the bacteria. For example, E.coli containing the ampicillin-resistance gene grows in the presence of this antibiotic while the product of the ß-galactosidase gene enables the bacteria to convert the ß-galactosidase substrate X-gal to a blue product. Similarly, E.coli containing the Lux operon produce colonies that glow in the dark. In this exercise, four different strains of E.coli are streaked onto agar plates containing media that selects for the different strains and that reveals variation in colony phenotype. Students record these variations and the results enable them to deduce the genotype of the strains as shown in the Table below.

Sufficient sterile materials are provided to prepare 32 plates and the experiment was designed for 8 groups of students. The exercise requires two 1 hour laboratory sessions.