Question

Describe how you would isolate a mutant that required histidine for growth and was resistant to penicillin.

Answer 1

My goal is to isolate a mutant that is resistant to the antibiotic penicillin and is a histidine auxotroph. A histidine auxotroph is a cell that is unable to synthesize the amino acid histidine. It contains some mutation in a gene that encodes for a product in the histidine biosynthetic pathway. Thus, a histidine auxotroph cannot grow without the presence of histidine in its growth media.