In а trаnsfоrmаtiоn experiment, a sample оf E. coli bacteria was mixed with a plasmid containing the gene for resistance to the antibiotic ampicillin (ampr). Plasmid was not added to a second sample. Samples were plated on nutrient agar plates, some of which were supplemented with the antibiotic ampicillin. The results of E. coli growth are summarized below. The shaded area represents extensive growth of bacteria; dots represent individual colonies of bacteria. Wild type E. coli are plated on plates 1 and 2, and E. coli with plasmid containing the ampicillin resistance gene is plated on plates 3 and 4. Plate 1 has no ampicillin,and is shaded representing extensive growth of bacteria. Plate 2 has ampicillin and is white with no colonies. Plate 3 has no ampicillin and is shaded representing extensive growth of bacteria. Plate 4 has ampicillin and has a dozen dots representing individual colonies of bacteria. Which of the following statements best explains why there are fewer colonies on plate IV than on plate III?