So I think I'll go ahead and make pools of colonies from the 5-min and 13-min treatments and enrich them for hypercompetent mutants by selecting for StrR transformants in log-phase cultures. Then tomorrow I can screen these for hypercompetence by our crude colony-transformation assay.
Why not also the 2-min treatment? OK, I'll include one pool of those too.
* One reason to not use the ~1000 CmR colonies from the 30-min dose is that these are less likely to have recombination tracts extending all the way from the CAT cassette to murE. That's because this segment contains two essential genes (ftsI & ftsL), and recombination tracts that cover the CAT-murE distance are much more likely to have had a lethal mutation in one of these genes than are tracts that don't reach to murE.