Adaptive mutation: general mutagenesis is not a programmed response to stress but results from rare coamplification of dinB with lac.
In a particular genetic system, selection stimulates reversion of a lac mutation and causes genome-wide mutagenesis (adaptive mutation). Selection allows rare plated cells with a duplication of the leaky lac allele to initiate clones within which further lac amplification improves growth rate. Growth and amplification add mutational targets to each clone and thereby increase the likelihood of reversion. We suggest that general mutagenesis occurs only in clones whose lac amplification includes the nearby dinB+ gene (for error-prone DNA polymerase IV). Thus mutagenesis is not a programmed response to stress but a side effect of amplification in a few clones; it is not central to the effect of selection on reversion.
Slechta
E Susan
ES
Microbiology Section, Division of Biological Sciences, University of California, Davis, CA 95616, USA.
Bunny
Kim L
KL
Kugelberg
Elisabeth
E
Kofoid
Eric
E
Andersson
Dan I
DI
Roth
John R
JR
D001426:Bacterial Proteins / Q000235:genetics*; D003227:Conjugation, Genetic; D019951:DNA Polymerase beta / Q000235:genetics; D029968:Escherichia coli Proteins; D017353:Gene Deletion; D016680:Genome, Bacterial; D007763:Lac Operon / Q000235:genetics*; D007785:Lactose / Q000378:metabolism; D016296:Mutagenesis / Q000235:genetics*; D010957:Plasmids; D012486:Salmonella typhimurium / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D012641:Selection, Genetic; D013997:Time Factors
D001426:Bacterial Proteins; C094399:DinB protein, E coli; D029968:Escherichia coli Proteins; D019951:DNA Polymerase beta; D007785:Lactose