Erroneous old dprA data

A few days ago I posted an old graph of transformation data that appeared to show that the DNA-protection gene dprA was not needed in cells whose recBC gene was knocked out. This was a result I didn't remember getting, so I was going to search through my old notebook (2003-04) to see if this was a real result.

This experiment turned out to not be in my notebook because it was done by an undergraduate working in the lab. She did good work, but I can't find her lab notes on our shelf of old notebooks. (I hereby vow to work with our new lab assistant to get these notebooks better labeled and organized.) My notes of her lab meeting presentations and other discussions don't directly address this point.

But I gradually remembered that her initial results had been wrong (maybe that the strain she thought was a double dprA recBC mutant was actually only a single recBC mutant?), and that correcting the error had eliminated this interesting result, replacing it with a more solid but less interesting one. I did find a copy of her final report . It shows clearly that the double mutant had the same transformation phenotype as the single dprA mutant, so she concluded that DprA's job is not to inhibit the nuclease activity of RecBC.