Question

Ways in which Chemical Control Agents May Affect Bacteria

1. Describe one way an antibiotic can inhibit peptidoglycan synthesis, state how that ultimately kills the bacterium, and give an example of such an antibiotic.

2. Describe one way an antibiotic can alter bacterial ribosomes, state how that ultimately inhibits or kills the bacterium, and give an example of such an antibiotic.

3. Describe one way an antibiotic can interfere with bacterial DNA synthesis, state how that ultimately kills the bacterium, and give an example of such an antibiotic.

Answer 1

1) An antibiotic like amoxicillin belongs to the beta-lactam antibiotics that contain a beta lactam ring in their molecular structure. They act by binding to penicillin binding proteins that is involved in the last step of peptidoglycan synthesis and inhibit the process of transpeptidation leading to activation of autolytic enzymes in bacterial cell wall. This leads to destruction of the cell wall and the lysis of the bacterial cell.

2) The ribosome is a major bacterial target for antibiotics as it is involved in protein synthesis that is required for growth and proliferation of the bacterial cell. Antibiotics inhibit ribosome function either by interfering with mrna translation or by blocking the formation of peptide bond. Both of these processes are required for its growth and proliferation and inhibition to this may lead to death.

For example- Antibiotics like tetracycline binds to the antibiotic binding sites of the 30S subunit of the ribosome and hinders the process of mrna synthesis

3) DNA replication requires the activity of the topoisomerases II . These enzymes relaxes the supercoiled DNA molecules and initiates transient breakages and rejoins phosphodiester bond in the super helical turns in the closed circular DNA of bacteria and thus makes the DNA strand available for DNA polymerase.

Quinolones interfere with the activity of topoisomerases II and thus preventing DNA replication that may lead to inhibition in growth and proliferation of bacterial cell and ultimately causing death.