Question

How do facultative anaerobes differ from aerotolerant anaerobes?

Answer 1

Mostly the organisms require oxygen for their growth and survival but some organisms do not require oxygen for survival and are known as anaerobes.

Complete answer:
The anaerobic organisms do not require any oxygen molecules for their growth and survival. But the anaerobic organisms are also classified into different types such as facultative anaerobes, aerotolerant anaerobes, obligate anaerobes, etc.

Facultative anaerobes are those organisms that mainly live in presence of oxygen and use oxygen for the production of energy but in the case where oxygen is not available, it can still obtain energy through anaerobic respiration that is by fermentation. That is they are anaerobes only in absence of oxygen. Thus known as facultative anaerobes.

The aerotolerant anaerobes do not use oxygen at all and obtain energy only through anaerobic respiration but these aerotolerant anaerobes are not affected by the presence of oxygen molecules.

Hence the facultative anaerobes can use oxygen molecules for the production of energy in the form of ATP and their growth. The facultative anaerobes are quite flexible between being aerobic in presence of oxygen and being anaerobic in absence of oxygen but the aerotolerant anaerobes cannot use oxygen for the production of energy and can only grow in anaerobic conditions.

Note: Examples of facultative anaerobes include aquatic species such as nereid polychaetes, fungus such as saccharomyces cerevisiae, and a large number of bacterias such as E.coli, salmonella, etc.
Examples of aerotolerant anaerobes are C.histolyticum, C.carnis, streptococci, campylobacter jejuni, etc.