Why is oxygen dangerous to microorganisms?

Answer 1

Oxygen releases free radicals, which are harmful to organisms. While aerobic organisms have the protective mechanisms in their structure to break down these free radicals, anaerobic organisms do not.

Answer 2

Microbial cells have enzymes [superoxide dismutase (SOD), catalase and non-specific peroxidasesthat] can be damaged when exposed to oxygen and any organism that desires to reside in oxygen-present environments must have methods to protect those enzymes and hence themselves. Oxygen will react in the cell to form two major toxic products; hydrogen peroxide and superoxide. But unfortunately strict anaerobes do not posses these protective mechanisms and hence cannot survive in the presence of air and are hence restricted to anaerobic environments.

Answer 3

Oxygen is highly reactive and likes to combine with elements common in organic molecules such as carbon and hydrogen. If a lot of carbon and hydrogen atoms start leaving their molecules to join with all the oxygen in the atmosphere those molecules change and no longer do the things they were supposed to do such as help feed or protect the cell they are part of.

Answer 4

Oxygen reacts with cellular matrix, producing reactive oxygen species [ROS] and free radicals. These free radicals cause oxidative damage to the bacteria, due to lack of certain enzymes and cause toxic injury.

Answer 5

Some bacteria don't have the enzymes (catalase, superoxide dismutase) for getting rid of oxygen radicals, and die because of their formation