Induction of mutants with altered DNA composition: effect of ultraviolet on Bacterium paracoli 5099.

The culture of Bacterium paracoli 5099 represents a favorable system for induction of mutants with altered DNA base composition. The frequency of induction of these mutants by ultraviolet radiation is strongly dose-dependent, and has a peak at the ultraviolet exposure equal to 860 ergs. On both sides of this maximum the rate of appearance of mutants decreases, and with the exposures less than 350 and more than 1900 ergs per square millimeter, mutants with altered DNA base composition do not appear at all.