Forward mutation in Escherichia coli and gene conversion in Saccharomyces cerevisiae compared quantitatively with reversion in Salmonella typhimurium.

Forward mutation to c'azetidine carboxylic acid resistance in Escherichia coli WP2 and gene conversion at the tryptophan locus in Saccharomyces cerevisiae D4 were compared with reversion in strains TA98, TA100 and TA1537 of S. typhimurium for sensitivity and range of agents detected. Eight mutagens of known and differing modes of action were used in assays in liquid culture. It was concluded that neither non-specific system could replace all the Salmonella strains in a programme of mutagenicity assays in liquid culture; however, E. coli caca(r) could adequately replace strains TA100 and TA1537, provided that TA98 was retained to detect certain types of frame-shift mutation. Also gene conversion would prove useful in the assay of antibacterial agents.