Response of Escherichia coli auxotrophs to heat after treatment with mutagenic alkyl methanesulfonates.

Strauss, Bernard S. (The University of Chicago, Chicago, Ill.). Response of Escherichia coli auxotrophs to heat after treatment with mutagenic alkyl methanesulfonates. J. Bacteriol. 83:241-249. 1962.-Heating in buffer at 48 C resulted in a large increase in the frequency of revertants obtained after treatment of restingphase cells of Escherichia coli strain WP-2 (a tryptophan-requiring mutant of strain B/r) with ethyl methanesulfonate. This effect was not obtained with the mutagenic homologue, methyl methanesulfonate. Cells treated with ethyl methanesulfonate lost their sensitivity to heat soon after the start of incubation in growth medium; chloramphenicol added to the growth medium preserved the sensitivity. Cells in the exponential growth phase which were treated with ethyl methanesulfonate were rapidly killed by heat treatment. Methyl methanesulfonate was more effective as a killing agent than the ethyl derivative. Heat effects on mutation frequency were obtained with a second tryptophan-requiring mutant of E. coli B/r and with a tryptophan-requiring mutant of E. coli K-12.