Direct evolution allows for the selection of certain desired properties not naturally found in the wild type. There is a designed push for natural selection to occur to amplify a trait.
History
Mutants of E. coli able to grow on propylene glycol were selected for ethylene glycol enzymatic breakdown after ethyl methane sulfonate mutagenesis. The culture conditions strongly selected for ethylene glycol utilizing mutants, by having ethylene glycol as the sole carbon source in liquid culture. Through directed evolution, colonies were continuously streaked on ethylene glycol plates for three more generations, in order to isolate ethylene glycol degrading mutants. Through spectrophotometric assays, increased activities of glycolaldehyde reductase and glycolaldehyde dehydrogenase were observed in the ethylene glycol isolates.
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