Question

On ampicillin medium, Do satellite colonies express beta-lactamase?

Answer 1

Answer: The beta-lactamase gene is not expressed by the satellite colonies as they are not transformed by the plasmid.

Explanation: The bacterial cells that are transformed with the plasmid having an ampicillin resistance gene. This gene codes for the beta-lactamase enzyme, which is secreted in the medium. This beta-lactamase enzyme causes the hydrolysis of the ampicillin and thus allows the growth of the transformed cell.

Due to the secretion of the beta-lactamase enzyme in the culture medium, a small zone is created, where selective pressure of ampicillin is absent, and thus non-transformed satellite colonies can grow in this region.

The satellite cells will not be able to grow ,if they are transferred in the medium having fresh ampicillin because they do not have the beta-lactamase enzyme.