Satellite colonies in pGLO E. coli culture

[darylc123]

Hi,

I am planning to conduct an experiment involving satellite colonies. The experiment is based off the pGLO transformation lab that inserts an ampicillin resistance gene, araC, and GFP gene into E. coli. Once grown in LB/amp/ara culture, the transformed E. coli secrete beta lactamase, which breaks down the surrounding ampicillin and allows non-transformed "satellite" bacteria to grow around it.

I'm having some trouble coming up with a suitable experiment to research the satellites. So far my ideas are to investigate the correlation between the ampicillin concentration and number/amount of satellite colonies. So if the ampicillin is increased, the number of satellites should go down. But how would I measure the satellites? Should I count them, measure the radius of the whole colony, or test for the presence of beta lactamase?

If you have any ideas, please help! Thanks!

[JackBean]

And do you need to measure them? Isn't just "present/absent" good enough?

[darylc123]

They're present at all concentrations.

[JackBean]

Well, than I don't understand the principle :-/