Satellite Colonies - (Oct/21/2008 )
Can anybody come up with a brief description of as to why satellite colonies appear more easily on ampcillin plates than on other antibiotic plates e.g the ones containing kanamycin or tetracyclin.
Probably amp degrade faster than the other antibiotics? But I aint sure though. =)
that's one of it but truly the main reason lies in the mechanism of antibiotic resistance for amp. For amp the beta lactamase is secreted out of the cell which then make area around the colony to be less concentrated in amp.
The beta-lactamase enzyme that degrades amp is secreted, as opposed to those that degrade kn or tet, so any transformants produce an amp-free zone around them. Statistically, some of the non-transformed cells will survive long enough to be saved by this amp-free area, and will start growing, but it takes time for the recovery which is why satellites only appear after an extended incubation.
Some antibiotic resistance doesn't rely on enzymatic degradation of the antibiotic -- some resistance is mediated by the cell having the ability to pump the drug out of the cell, other resistance is mediated by the cell having a mutation effecting the target of the drug, so the drug's mechanism of action is thwarted.
Some drugs are more quickly bacteriolytic, whereby if you're not resistant, you're dead, so there's no hope of arising later as a satellite colony.