Antimutagenic specificity against spontaneous and nitrofurazone- induced mutations in Escherichia coli K12ND160

Escherichia coli K12ND-160 possesses characteristics which make it highly suitable for studies on mutagenic/antimuta-genic specificity and has been used to investigate such effects for several agents. Nitrofurazone (NFZ) was used as a mutagen at non-lethal concentrations; it causes mutation from fucose sensitivity to resistance (Fucs — FucR) and from inability to utilize melibiose to melibiose utilization (Mel ~ —Mel+), but does not induce mutations from deoxy-galactose sensitivity to resistance (DGAS—DGAR). Caffeine is mutagenic for reversions from lactose non-utilization to utilization (Lac " —Lac+) and mutations from Fucs—FucR, but it is antimutagenic for mutations from 6-azauracil sensi-tivity to resistance (AzaUs—AzaUR) and Mel ~ —Mel+ rever-sions and produces no effect on spontaneous DGAS—DGAR mutations. Added guanosine and cytidine (G+C at 100 /tg/m