Isolation of mutagens from bacterial nutrients containing beef extract.

The enhanced rate of mutation of Salmonella strain TA1538 (Ames) by microsomes results from the presence of about 2--5 ppm of microsome-activatable mutagens in bacterial nutrient broths that contain beef extract. Since mutagens toward Salmonella are likely to be carcinogenic, the data have significant implications for the problem of carcinogenesis.