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Do people use random mutagenesis (say using UV) to generate host variants that have high expression of a metabolite / enzyme? I've seen it mentioned as a strategy but it confuses me as to why.

How does that compare to using Directed Evolution for the same purpose? Intuitively, random mutagenesis seems highly inefficient (since you have no control over which genes you mutate) given the combinatorial explosion even in something like E Coli's genome size. Am I making a mistake in this reasoning?

What are situations where one may prefer random mutagenesis over directed evolution? Are there any pros and cons to consider?

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Well, you already mentioned it. Random mutagenesis (with UV or chemical mutagens) targets the entire genome and you select the organism for certain traits.

In a directed evolution experiment, you are just targeting a gene or a group of genes. With the progress of synthetic biology, it might be possible to synthesize small genomes (already shown by Craig Venter and group) and apply directed evolution methodology genome wide. This would still not be considered directed, as the mutations are actually random over the genome.

The pros and cons depend on what exactly you aim to do.

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  • $\begingroup$ Thanks! The aim is something like this: I'm interested in getting yeast to express a secondary metabolite by inserting a hetrologous gene. The goal is to develop & select a yeast strain that produces high levels of the precursor substrate. $\endgroup$ – curious_cat Apr 25 '16 at 9:00
  • $\begingroup$ @curious_cat That is the ultimate goal. In that case you can go for random mutagenesis. However, if you are improving the catalysis rate of a specific enzyme, lets say, then apply directed evolution to that specific gene. $\endgroup$ – WYSIWYG Apr 25 '16 at 9:03
  • $\begingroup$ Thanks! So it isn't entirely impractical to attempt random mutagenesis? i.e. With 12 Million base pairs & random mutation is it a viable strategy? Have other attempts using similar approaches succeeded? $\endgroup$ – curious_cat Apr 25 '16 at 10:55

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