Question

List two classes/types of antibiotic for each of the following targets: Cell wall Synthesis and Protein Synthesis. Describe how this class of antibiotics specifically work and why this makes them selectively toxic.

Answer 1

Inhibitors of cell wall synthesis

1. ??Penicillin - It is a beta-lactam broad spectrum antibiotic that inhibits transpeptidation enzymes involved in the crosslinking of the polysaccharide chains of the bacterial cell wall peptidoglycan. It also activates cell wall lytic enzymes.
2. Bacitracin - It is a narrow spectrum antibiotic which is produced by organisms of the licheniformis group of Bacillus subtilis var Tracy. It inhibits cell wall synthesis by interfering with action of the lipid carrier that transports wall precursors across plasma membrane.  

Inhibitors of protein synthesis

1. Streptomycin - It is effective against gram positive, gram negative and mycobacteria. It binds to 16S rRNA of 30S subunit and cause misreading of mRNA and inhibits protein synthesis. This eventually leads to microbial death. Therefore, it is bactericidal.
2. Erythromycin - It is bacteriostatic in nature ?. It binds to 50S subunit and interferes with aminoacyl translocation, preventing the transfer of the tRNA bound at the A site of the rRNA complex to the P site of the rRNA complex. As a result, the A site remains occupied and the addition of an incoming tRNA and its attached amino acid to the nascent polypeptide chain is inhibited. Production of functionally useful proteins is blocked.