What is the mechanism by which steam under pressure sterilization kills microorganisms?

Steam under pressure sterilization, commonly known as autoclaving, effectively eliminates microorganisms primarily through the mechanism of coagulation of plasma proteins. When materials are subjected to high-pressure steam at temperatures typically around 121 degrees Celsius, the heat and moisture cause proteins within the cells of the microorganisms to denature and coagulate.

This coagulation process disrupts the structural integrity of the proteins necessary for the microorganism's survival, leading to cell death. As proteins are vital for numerous cellular functions, including metabolism and replication, their inactivation drastically reduces the viability of the microorganism.

While other mechanisms, such as dehydration of DNA, denaturation of bacterial membranes, and oxidation of cell walls, may contribute to microbial inactivation in different sterilization processes, they are not the primary action occurring during steam sterilization. The success of this method relies heavily on the ability of the moist heat to penetrate the materials being sterilized and effectively lead to the coagulation of proteins, resulting in a reliable and thorough sterilization process.