Why was ampicillin included in the overnight culture?

Why was ampicillin included in the overnight culture?

• A. To allow transformed E. coli cells to grow and divide.
• B. To kill non-transformants.
• C. To provide carbon source.
• D. To inhibit growth of all cells.

Answer: (A)

Ampicillin acts as a selective pressure in transformation experiments. The plasmid you introduce into E. coli carries an ampicillin resistance gene, so only cells that took up the plasmid can survive and keep growing in the presence of the antibiotic. Non-transformants, which lack the resistance, are killed or unable to divide. This selective environment enriches for cells that carry the plasmid, making it easier to identify and study the transformed population. Ampicillin isn’t a carbon source, and it doesn’t suppress growth of all cells—only the ones without resistance are affected.

Ampicillin acts as a selective pressure in transformation experiments. The plasmid you introduce into E. coli carries an ampicillin resistance gene, so only cells that took up the plasmid can survive and keep growing in the presence of the antibiotic. Non-transformants, which lack the resistance, are killed or unable to divide. This selective environment enriches for cells that carry the plasmid, making it easier to identify and study the transformed population. Ampicillin isn’t a carbon source, and it doesn’t suppress growth of all cells—only the ones without resistance are affected.