The entire biosynthetic pathway for the synthesis of the antibiotic pigment violacein is encoded on a 14.5 kilobase (kb) fragment of the Chromobacterium violaceum genome. When cloned into Escherichia coli, pigment synthesis is strongly expressed, as it is in a wide range of Gram-negative bacteria. Transposon mutagenesis resulted in a number of different phenotypes that correlated with transposon insertion sites in the gene cluster.