Students work in cooperative teams of mixed abilities to design and complete an experiment to isolate and characterize E. coli from different sources and to evaluate the differences in antibiotic susceptibility of their strains. This activity does not replace regular laboratory activities but is integrated into the normal lab to augment discussions on diversity, mutation, and antibiotic resistance. A formal report is used to assess the project. Because of potential risks of isolating multiply-antibiotic resistant bacteria, this experiment should be carried out with students who have proficiency in aseptic technique and appropriate regard for laboratory safety.