Question

“Table 4: Experiment Results”

“Antibiotic”	“Zone of Inhibition (mm)”	“Relative Effectiveness”
“Ampicillin”	10 mm	yes
“Kanamycin”	5 mm	minimal
“Penicillin”	15 mm	yes
“Control”	0 mm	no

1. What is the mechanism of action for each of the antibiotics used in this experiment?”

2. If a population of bacteria evolves resistance to penicillin, are these bacteria more likely to be also resistant to ampicillin or kanamycin? Explain your reasoning.”

Answer 1

Answer and explanation with image:

1) Penicillin and ampicillin both belong to a common group of antibiotics known as beta lactam antibiotics because they contain a beta lactam ring which binds with penicillin binding protein of bacteria.This binding inhibits transpeptidase enzyme thus preventing peptidoglycan synthesis. As peptidoglycan is an essential component of cell wall, cell wall could not be synthesised properly and bacteria become prone to lysis and thus get eliminated.

Kanamycin is an aminoglycoside antibiotic which inhibits 30s ribosomal subunit and thus prevents protein synthesis. Aminoglycosides are bactericidal antibiotics.

2) As penicillin and ampicillin belong to same group of beta lactam antibiotics and have same mechanism of action inhibiting cell wall synthesis, hence bacteria developing resistance to penicillin will likely be resistant to ampicillin but not to kanamycin (aminoglycosides has different mechanism of action and act by inhibiting protein synthesis).