The bacterial tryptophan reverse mutation assay with Escherichia coli WP2

The Escherichia coli WP2 tryptophan reverse mutation assay detects trp(-) t o trp(+) reversion at a site blocking a step in the biosynthesis of tryptop han prior to the formation of anthranilic acid. The different WP2 strains a ll carry the same AT base pair at the critical mutation site within the trp E gene. The assay is currently used by many laboratories in conjunction wit h the Ames Salmonella assay for screening chemicals for mutagenic activity. In general the WP2 strains are used as a substitute for, or as an addition to Salmonella strain TA102 which also carries an AT base pair at the mutat ion site. The assay is also recommended together with the Ames assay for da ta submission to regulatory agencies. National and international guidelines have been established for performing these mutagenicity assays. The E. coli WP2 assay procedures are the same as those described elsewhere in this volume for the Ames Salmonella assay (Mortelmans and Zeiger, 2000) with the exception that limited tryptophan instead of limited histidine is used. This chapter is an addendum to the previous chapter and the reader sh ould refer to the previous chapter for details regarding experimental proce dures and assay design. (C) 2000 Elsevier Science B.V. All rights reserved.