Bacterial Cell Ultrastructure: Peptidoglycan Architecture, Teichoic Acids & Periplasmic Transport - Dairy Microbiology | Agrigyan

• Inhibition of Peptidoglycan Cell Wall Biosynthesis by β-Lactams:
• $\beta$-Lactam Class (penicillins, cephalosporins, carbapenems):
• Covalently bind and inhibit penicillin-binding proteins (PBPs), which catalyze the transpeptidation cross-linking of peptidoglycan peptide side chains in the bacterial cell wall.
• Causes defective, mechanically fragile cell walls, triggering osmotic autolysis in growing cells.
• Conclusion: Beta-lactams (Option 3).

Correct option: (3) Beta-lactams

• Physiological Function of Teichuronic Acid:
• Phosphate Conservation Response:
• In phosphate-depleted environments, Gram-positive bacteria repress the synthesis of phosphate-rich teichoic acids and induce the synthesis of teichuronic acid (a phosphate-free polymer of glucuronic acid and N-acetylgalactosamine).
• This strategic replacement conserves cellular phosphate for essential DNA/RNA and phospholipid synthesis while maintaining the cell envelope's structural integrity and negative charge.
• Conclusion: It aids in conserving phosphate essential for cellular components (Option 2).

Correct option: (2) It aids in conserving phosphate essential for cellular components

• Periplasmic Transport Systems in Bacteria:
• Periplasmic Substrate-Binding Systems:
• In Gram-negative bacteria, periplasmic ABC transporters utilize specialized periplasmic binding proteins (B) that capture nutrients like sugars (A) (e.g., maltose-binding protein) and deliver them to membrane permeases for transport.
• Conclusion: (A) and (B) only (Option 1).

Correct option: (1) (A) and (B) only.