Which of the following is destroyed by oxygen?

Streptolysin O is an example of a virulence factor produced by certain organisms, primarily Streptococcus species. It is a cytolytic enzyme that can lyse red blood cells and is notably oxygen-sensitive. When exposed to oxygen, Streptolysin O undergoes denaturation, leading to the loss of its hemolytic activity. This characteristic makes it particularly useful in laboratory settings, where its presence can indicate the type of streptococcal infection.

The other options presented do not share the same sensitivity to oxygen. Botulism toxin is a potent neurotoxin produced by Clostridium botulinum but is not deactivated by the presence of oxygen; instead, it is more stable in anaerobic conditions. Catalase is an enzyme that breaks down hydrogen peroxide and is not destroyed by oxygen, as it actually requires oxygen to perform its function. Coagulase is an enzyme that causes clotting of blood plasma, and its activity is also not adversely affected by the presence of oxygen. Understanding the behavior of Streptolysin O in the presence of oxygen helps in diagnosing and understanding infections caused by Streptococcus species.