This paper is an invited Response to a recent Commentary P.L. Foster, Rev. Mut. Res. 436 1999 179-184 entitled 'Are adaptive mutations due to a decline in mismatch repair? The evidence is lacking'. The Commentary argues that no evidence exists supporting the idea that mismatch repair is limiting specifically during stationary-phase mutation. A primary concern of the author is to question the method that we used previously to measure growth-dependent mutation. In this method, mutation rates are calculated using counts of mutant colonies taken at times when those colonies arise, rather than at a predetermined, fixed time. Here we show further data that illustrate why this must be done to ensure accurate mutation measurements. Such accuracy was necessary for our published determination that mismatch repair proteins are not limiting during growth-dependent mutation, but become so during stationary-phase mutation. We review the evidence supporting the idea that stationary-phase reversion of a lac frameshift mutation occurs in an environment of decreased mismatch repair capacity. Those data are substantial. The data presented in the Commentary, in apparent contradiction to this idea, do not justify the conclusion presented there. (C) 1999 Elsevier Science B.V. All rights reserved.
Bibliographical noteFunding Information:
We thank the Editors in Chief of Reviews in Mutation Research for inviting this paper as a Response to a Commentary on our previously published work. We appreciate D. Brègeon, V.G. Godoy, M.S. Fox, F. Gizatullin, F. Taddei, and M. Radman for sharing unpublished results, H.J. Bull, M.-J. Lom-bardo, G.J. McKenzie, M.R. Motamedi, M. Radman, and E.L. Zechiedrich for discussions. Supported by an NSERC (Canada) postdoctoral fellowship to RSH and NIH (USA) grants R01CA77193 (MEW), R01GM53158 and R01AI43917 (SMR).
- Adaptive mutation
- Escherichia coli
- Mismatch repair
- Resting cell
- Spontaneous mutation
- Stationary-phase mutation