Mutagenesis of Escherichia coli (CSH50) by asbestos

The mutagenic character of richterite asbestos was detected in Escherichia coli strain CSH50, using a modified Ames test. Two sets of experimental plates which contained naturally occurring asbestos were used, to one set of which S-9 rat liver homogenate was added. Control plates contained no asbestos. Mutant colonies appeared in significantly greater frequency in both experimental sets as compared with controls, and experimental plates with rat liver homogenate contained the greatest number of mutant colonies. It is postulated that enzymes contained in rat liver metabolize some unknown mutagen introduced with the natural asbestos sample other than the inert richterite fibers themselves. This finding, together with the unlikelihood that bacterial cell walls could be easily penetrated by asbestos fibers, tends to negate fiber penetration as the mechanism of mutagenesis. The mutagenic mechanism operative in E. coli (CSH50) may be applicable to animal cell systems.