I'm starting the laser tweezers work with Bacillus subtilis cells rather than H. influenzae cells, for several reasons. B. subtilis cells are much bigger than H. influenzae cells, and also tougher. I've worked with them before and know how to make them competent. They take up DNA without any sequence specificity, so I can use them with the same bead-attached H. influenzae DNA that I'll use for the H. influenzae cells. And they've previously been used for optical tweezers measurement of DNA uptake. So they're an excellent positive control for the H. influenzae experiments I want to do.
Today I streaked out the wildtype and auxotroph (trp- met-) strains from some 20-year-old slants; they're growing up fine. And I made the defined media needed for competence induction, and poured some plates with and without tryptophan and methione, and streaked both strains on all the kinds of plates to test that I've made them correctly. I found a DNA stock from the wildtype strain in the fridge. It's about 19 years old but I expect it will still be fine. If the transformations don't work well I'll make fresh DNA.
A new kind of problem
12 hours ago in RRResearch