Observing the effects of six different antibiotics on Gram-negative and Grampositive bacteria will give your students a clearer understanding of how antibiotics fight off infection. The commercial antibiotics included are chloromycetin, erythromycin, novobiocin, penicillin G, streptomycin, and tetracycline. The kit also includes tube cultures of Bacillus subtilis and Escherichia coli, instructions, and materials for one demonstration.