You are working in a bacterial genetics laboratory. You are studying the biosynthetic pathway for the amino acid arginine in e. Coli and have two mutant strains: arge, and argg that were generated by transposon mutagenesis. You need to perform an experiment with these two arginine biosynthesis mutants, and so you first streak them from your stock culture onto la so that they have access to arginine. Once the strains have grown on the la plate, you streak individual colonies of both mutants onto m9, m9 ornithine, and m9 l-argininosuccinate plates that you purchased from a reputable supplier. As expected, the arge mutant cannot grow on m9 unless ornithine is supplemented. Unexpectedly, the argg mutant can grow on all three plates, whether l-argininosuccinate is supplemented or not. What is the most plausible explanation for these unexpected results?
