A rushed post after another drought
Again, I've left little time to blog... but some intriguing results that shall be expanded upon in the next blog. After two days of timecourses - the first day foiled by slow growing cells - to test the effects of nucleotide supplementation in MIV on competence development in KW20 and hypercompetence mutants (sxy-1 and -2), the transformation frequency results are most surprising. AMP does not repress competence as strongly in the hypercompetence mutants as KW20, but GMP appears to have an equal effect on all strains. This suggests that the mutations have somehow lessened sxy's sensitivity to AMP pools, and moreover that it is AMP pools that change as the cell shifts from exponential growth to stationary phase. The GMP results are very interesting because, first, they show that although sxy hypercompetence mutants start with more Sxy protein when they are transferred to MIV, they do not have enough to stimulate competence, and second that the mutations specifically affect AMP but GMP repression. If sxy is a riboswitch and AMP and GMP are analogs to which it binds, we would expect the mutations to disrupt both equally... Next week the protein and RNA work should help us resolve a better model as to what's going on.