Starvation-Induction and Base Excision Repair of
G -> T Mutations in Escherichia coli

Joline Shu¹ and Terence M. Murphy²,

Section of Plant Biology, University of California, One Shields Ave., Davis, CA 95616 USA

(Presented at the 2004 Annual Meeting, American Society for Photobiology, Seattle)

Objectives

In this study we use beta-galactosidase mutants that revert to active form specifically through a G -> T transversion, to ...
a) compare the rates and time courses of spontaneous reversion to lac+ in mutM+ and mutM- strains, demonstrating that base excision repair varies with time in stationary phase;
b) compare reversion in lactose and glucose media, showing a strong effect of the selective agent lactose on the rates of appearance of revertants;
c) measure the influence of metabolic stress in mutagenesis by varying glucose and O₂ concentrations, demonstrating an unexpectedly strong inhibition of reversion by high glucose and O₂.

Background

Base excision repair, initiated by FPG, limits reversion rate

Base excision repair gains effectiveness as the culture ages

Reversions to lac+ are favored by the presence of lactose

Reversion rate depends on glucose concentration

Reversion rate is increased by low O2 and decreased by high O2 concentrations

All revertants show G -> T transversions

Conclusions, References, Acknowledgements

¹Present address: School of Medicine, University of California, Irvine

²Correspondence to: Terence M. Murphy, Section of Plant Biology, One Shields Avenue, University of California, Davis, CA 95616; FAX +1 (530) 752-5410; e-mail tmmurphy@ucdavis.edu