Question A student inoculates Escherichia coli into two test tubes containing the same sterile liquid medium, except that the first tube also contains a drop of a chemical with an antimacribial effect. After 24 hours of incubation, the first tube remains clear, whereas the second tube has become cloudy with bacteria. Design an experiment to determine whether this amount of the antimicrobial chemical is bacteriostatic or bactericidal against E.coli ?
You could repeat the procedure but first use transformation (or another gene editing tool) to insert GFP sequence after the promoter of a commonly expressed gene. Then inoculate the e coli into two tubes with liquid media as the student did, one with the antimicrobial and one without. You expect the one without to glow bright green. If you have a bactericidal antimicrobial, no light should be detectable emitting from the second tube. If it is bacteriostatic, you should detect a small amount of light (perhaps you could use an instrument to detect it?) You could also use a different transgene, perhaps causing the bacteria to make a product that accumulates over time so you can detect it. But the main point would be to use the fact that bacteriostatic drugs do not kill bacteria, so they should still be metabolically active. What do you think?
