During autoclaving at 121°C/15 psi for 15 minutes, the killing of bacterial endospores depends on moist heat achieving which specific lethal effect that dry heat does NOT achieve at the same temperature?
- A Denaturation of proteins via hydrolysis of peptide bonds, requiring lower activation energy than dry-heat oxidation ✓
- B Rupture of covalent disulfide bonds in spore coat proteins
- C Destruction of dipicolinic acid-calcium chelate in the spore core
- D Disruption of the cortex muramic lactam structure by steam under pressure
Explanation
Moist heat (steam) kills by coagulation/denaturation of proteins through hydrolysis of peptide bonds; water molecules directly participate in breaking peptide bonds (hydrolysis), lowering the activation energy required for denaturation compared to dry heat which kills by oxidation; this is why moist heat sterilizes at 121°C while dry heat requires 160-170°C. At the same temperature, moist heat achieves the same protein denaturation endpoint at much lower temperature because of water-assisted hydrolysis. Dipicolinic acid is released during germination (not directly lysed by moist heat). Cortex degradation occurs after membrane permeabilization.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.