Obligate anaerobes grow in (DNB Dec-2010)
|A||Absence of air|
|B||Absence of O2|
|C||Presence of CO2|
|D||Presence of CO2 or O2|
a. Obligate anaerobes grow only in absence of oxygen. E.g. Clostridia, Bacteroides.
b. They can not grow in the presence of oxygen as they lack the enzyme Catalase to get rid of toxic oxygen radicals. However, many anaerobes causing human infections are aerotolerant (able to survive but not multiply in the presence of 2-8% oxygen) as they have superoxide dismutase.