If a Bacterial Colony Is Grown in a Medium That

If a bacterial colony is grown in a medium that is rich in the amino acid lysine, cell division proceeds rapidly and the colony grows steadily.If the lysine concentration drops, cell division slows; if the lysine concentration is restored, cell division resumes.Lysine is thus a(n)

A) fertilization signal.
B) ori site.
C) reproductive signal.
D) oncogene.
E) fission activator.