title: Evolution of extreme resistance to ionizing radiation via genetic adaptation of DNA repair.
abstract: By directed evolution in the laboratory, we previously generated populations of Escherichia coli that exhibit a complex new phenotype, extreme resistance to ionizing radiation (IR). The molecular basis of this extremophile phenotype, involving strain isolates with a 3-4 order of magnitude increase in IR resistance at 3000 Gy, is now addressed. Of 69 mutations identified in one of our most highly adapted isolates, functional experiments demonstrate that the IR resistance phenotype is almost entirely accounted for by only three of these nucleotide changes, in the DNA metabolism genes recA, dnaB, and yfjK. Four additional genetic changes make small but measurable contributions. Whereas multiple contributions to IR resistance are evident in this study, our results highlight a particular adaptation mechanism not adequately considered in studies to date: Genetic innovations involving pre-existing DNA repair functions can play a predominant role in the acquisition of an IR resistance phenotype. DOI: http://dx.doi.org/10.7554/eLife.01322.001.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, United States.
authors.forename: Rose T
authors.initials: RT
authors.lastname: Byrne
authors.forename: Audrey J
authors.initials: AJ
authors.lastname: Klingele
authors.forename: Eric L
authors.initials: EL
authors.lastname: Cabot
authors.forename: Wendy S
authors.initials: WS
authors.lastname: Schackwitz
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Martin
authors.forename: Joel
authors.initials: J
authors.lastname: Martin
authors.forename: Zhong
authors.initials: Z
authors.lastname: Wang
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Wood
authors.forename: Christa
authors.initials: C
authors.lastname: Pennacchio
authors.forename: Len A
authors.initials: LA
authors.lastname: Pennacchio
authors.forename: Nicole T
authors.initials: NT
authors.lastname: Perna
authors.forename: John R
authors.initials: JR
authors.lastname: Battista
authors.forename: Michael M
authors.initials: MM
authors.lastname: Cox
mesh_terms: D000220:Adaptation, Biological; D004252:DNA Mutational Analysis; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D009154:Mutation; D011839:Radiation, Ionizing
chemical_list: D029968:Escherichia coli Proteins; D045643:DNA Repair Enzymes
keywords: DNA repair; evolution; extremophile; ionizing radiation; mutation