Well, I think I get it now. I was getting an odd phenotype
for the Δhfq sxy-1 double mutant that suggested that this mutant was more
competent than the sxy-1 single mutant. This is weird since knocking out Hfq in
all other conditions tested so far has a negative effect. I tested the other
hypercompetent sxy point mutations in a Δhfq background and again, I only see a
negative effect:
And of course...
This has been eating at me for a long time now. Last lab
meeting, I think it was Rosie who asked whether or not the Δhfq sxy-1 strain
was accidently mixed-up with the Δhfq murE749 strain. Thinking about it more, I
realized that when Rosie had originally preformed the initial characterization
of the Δhfq mutants, her lab notes had swapped the two strains in some places.
Looking at the data, it also seems reasonable that what I’ve been calling Δhfq
murE749 is actually Δhfq sxy-1:
I’ll have to experimentally verify this by using a
restriction endonuclease (Mnl I) that has an additional cleavage site in the
murE749 mutant. It’s nice to know that this will probably answer a lot of
questions that I have, but I am now left with no leads to identify where the
Hfq effect on competence occurs. Science is a harsh mistress.
