Question

Why oxygen is toxic to obligate anaerobes? How do you classify microorganisms based on their oxygen requirements? Name the groups and explain each group.

Answer 1

Oxygen contains two unpaired electrons one is reduced to superoxide and the other to hydrogen peroxide in cells. Aerobic organisms produce catalase and superoxide dismutase to counteract these products , whereas these obligate anaerobs either don't produce them or produce them in very less amount . Which leaves them toxic to oxygen .

Microorganisms can be classified into groups according to their oxygen consumption;

1. Obligate aerobes : requires oxygen to survive.

2. Microaerophilic : requires low oxygen .

3. Facultative anaerobes : respires aerobically until oxygen is depleted and then comes to fermentation anaerobically .

4. Obligate anaerobes : lacks superoxide dismutase and catalase , is toxic to oxygen .