Adaptive Mutagenesis Research Articles

Reverse Interpretation: A Hypothetical Selection Mechanism for Adaptive Mutagenesis Based on Autoregulated mRNA Stability

The problem of adaptive mutagenesis is examined under the assumption that selection occurs through the interaction of cognate mRNA and protein molecules, a phenomenon that has been considered to lead to differential mRNA decay (Kyrpides & Ouzounis, 1993, J. theor. Biol. 163, 373-392). Based on the stereochemical hypothesis, we speculate that the origin of this process relies on an extended form of molecular interactions. This mechanism, termed reverse interpretation, predicts the selective amplification of successful molecular forms with the capability of their immortalization through reverse transcription, in a manner that resembles, but is not equivalent to, reverse translation. Finally, we argue that the proposed mechanism conforms with the Darwinian view of evolutionary change, if variability is considered to be a property of molecular and not cellular populations.

Mutant bias in nonlethal selections results from selective recovery of mutants.

We have characterized a nonlethal selection for mutations that allow Escherichia coli to grow on large maltodextrins (Dex+) in the absence of the lamB encoded maltoporin LamB. These Dex+ mutations occur before and after imposition of the selection and the selection does not result in a general increase in mutagenesis. The recovered Dex+ mutations are almost exclusively mutations that alter the ompF gene that encodes a major E. coli porin, OmpF even though analogous mutations in the homologous ompC gene, which encodes the OmpC porin, can confer a Dex+ phenotype. We show that the bias for ompF mutations results from a biased recovery and that the genetic background of the starting strain and the selection itself influences the type of mutants that are recovered. When we use a strain carrying an amber mutation in the lamB gene we observe the same preference for ompF mutations as when we start with a lamB deletion strain. In addition, we show that there is no preferential mutagenesis of the lamB gene during the selection which induces transcription of the lamB gene. We present evidence that the biased recovery of mutants observed in this selection does not result from adaptive or directed mutagenesis and that the phenotypic fitness which allows recovery of Dex+ mutants involves more than the increased ability to take up maltodextrins.

A mechanism for adaptive mutagenesis

A mechanism for adaptive mutagenesis