Mutagenicity test for unstable compounds, such as 5,6-dihydroxyindole, using an Escherichia coli HB101/pBR322 transfection system.

A mutagenicity test for unstable chemical compounds has been devised. The test makes use of (i) in vitro treatment of plasmid pBR322 with the putative mutagen (ii) subsequent transfection of Escherichia coli HB101; (iii) selection either on tetracycline- or ampicillin-containing Eugon agar (iv) cross-antibiotic replica plating and recovery of single antibiotic resistant colonies (v) restriction analysis of pBR322 isolated from single antibiotic resistant colonies. In this work the test has been used to assess the mutagenicity of 5,6-dihydroxyindole, a cytotoxic intermediate of melanin biosynthesis.