This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Shlaes, D. M. Articles by Barbour, S. D. Search for Related Content PubMed PubMed Citation Articles by Shlaes, D. M. Articles by Barbour, S. D.

 Previous Article  |  Next Article 

J Bacteriol. 1972 September; 111(3): 723-730
Copyright © 1972 American Society for Microbiology. All Rights Reserved.

Excision Repair Properties of Isogenic rec^– Mutants of Escherichia coli K-12¹

^a Department of Microbiology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106

ABSTRACT

We have examined the excision repair properties of isogenic rec^– and uvr^– strains of Escherichia coli K-12. A recB^–recC^– strain excises dimers at a rate nearly that of the rec⁺ parent, reaching the same extent of excision after a 1-hr postirradiation incubation. recA^– and recA^–recB^– strains excise 75 to 80% of the dimers excised by their rec⁺ parent, whereas a uvrB^– strain excises no dimers during a 1-hr incubation. The doses of ultraviolet light (254 nm) required to reduce survival to 37% of the original population are 8 ergs/mm² for recA or recA recB mutants, 5 ergs/mm² for the uvrB^– strain, 30 ergs/mm² for the recB recC mutant, and 230 ergs/mm² for the wild-type parent. From these data one cannot account for the ultraviolet light sensitivity of rec^– strains on the basis of their excision repair properties. We conclude that rec gene products play no significant role in the early steps of excision repair. The assay we have used for excision of thymine dimers is a modification of the Carrier-Setlow technique, and is described in detail in the Appendix to this paper. To show the properties and validity of this method, results of experiments with thymine dimers formed in vitro and in vivo in E. coli K-12 are presented. These results show our method to be reproducible and sensitive to 0.005% of the total radioactive thymine present in thymine-containing dimers.

¹ This is the fifth paper in a series entitled, "Biochemical and Genetic Studies of Recombination Proficiency in Escherichia coli K-12."