Question

Lysozyme works by attacking peptidoglycan in bacterial cell walls. However, it is not the only antibacterial substance that affects peptidoglycan. Why do you think this is so?

Answer 1

Two types of antimicrobial drugs work by inhibiting or interfering with cell wall synthesis of the target bacteria. Antibiotics commonly target bacterial cell wall formation (of which peptidoglycan is an important component) because animal cells do not have cell walls. The peptidoglycan layer is important for cell wall structural integrity, being the outermost and primary component of the wall.

The first class of antimicrobial drugs that interfere with cell wall synthesis are the ?-Lactam antibiotics (beta-lactam antibiotics), consisting of all antibiotic agents that contains a ?-lactam nucleus in their molecular structures. This includes penicillin derivatives (penams), cephalosporins (cephems), monobactams, and carbapenems. ?-Lactam antibiotics are bacteriocidal and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls. The final step in the synthesis of the peptidoglycan is facilitated by penicillin-binding proteins (PBPs). PBPs vary in their affinity for binding penicillin or other ?-lactam antibiotics.

Bacteria often develop resistance to ?-lactam antibiotics by synthesizing a ?-lactamase, an enzyme that attacks the ?-lactam ring. To overcome this resistance, ?-lactam antibiotics are often given with ?-lactamase inhibitors such as clavulanic acid.

The second class of antimicrobial drugs that interfere with cell wall synthesis are the glycopeptide antibiotics, which are composed of glycosylated cyclic or polycyclic nonribosomal peptides. Significant glycopeptide antibiotics include vancomycin, teicoplanin, telavancin, bleomycin, ramoplanin, and decaplanin. This class of drugs inhibit the synthesis of cell walls in susceptible microbes by inhibiting peptidoglycan synthesis. They bind to the amino acids within the cell wall preventing the addition of new units to the peptidoglycan.

PENICILLIN It interferes with the synthesis of peptidoglycan. This weakens the cell walls of dividing bacteria, so they burst and die because of osmotic pressure. Finally, we learned that penicillin is a narrow-spectrum antibiotic and is more effective against Gram-positive bacteria.