The previous Bioscreen experiment failed because, as we suspected, the vial we purchased didn't contain the expected mg of bicyclomycin. The highest concentration we tested (20 µg/ml) caused only a very slight slowing of growth, so we contacted the supplier and had them send us a new vial. This contained more visible powder than the previous one had, although still a very tiny amount), and we used it for a new Bioscreen experiment, testing concentrations up to 10 µg/ml.
This time the 10 µg/ml culture showed a substantial slowing of growth. We also saw smaller decreases in growth, proportionally, with the lower concentrations. Although the effects were smaller than we expected from the reported MIC (minimum inhibitory concentration of 3 µg/ml, we think we can go on to do our experiment.
Before we do the big competence-induction experiment we should really do another Bioscreen run to test the higher bicyclomycin concentrations we would need to include in the big experiment. We can't afford to use up much bicyclomycin to do this, so we'll decrease the numbers of replicate wells we use:
The summer student thinks she can do this tomorrow (she'll fill the other wells with plain medium (no cells) as her contamination control), and then we'll be able to do the big experiment on Friday!
Metereca: Crossing the Divide
14 hours ago in Catalogue of Organisms