Biology:Facultative aerobic organism

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Aerobic and anaerobic bacteria can be identified by growing them in test tubes of thioglycollate broth:
1: Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest.
2: Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest.
3: Facultative aerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. They gather mostly at the top because aerobic respiration generates more ATP than either fermentation or anaerobic respiration.
4: Microaerophiles need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube but not the very top.
5: Aerotolerant organisms do not require oxygen as they metabolise energy anaerobically. Unlike obligate anaerobes, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube.

A facultative aerobe is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation or anaerobic respiration if oxygen is absent.[1][2] An obligate aerobe, by contrast, cannot make ATP in the absence of oxygen, and obligate anaerobes die in the presence of oxygen.[3]

Some examples of facultative aerobic bacteria are Staphylococcus spp., Streptococcus spp.,[4] Escherichia coli, Salmonella, Listeria spp.[5] and Shewanella oneidensis. Certain eukaryotes are also facultative aerobes, including fungi such as Saccharomyces cerevisiae[6] and many aquatic invertebrates such as Nereid (worm) polychaetes.[7]

See also


  1. Hogg, S. (2005). Essential Microbiology (1st ed.). Wiley. pp. 99–100. ISBN 0-471-49754-1. 
  2. Goddard, Andrew (2017). "What is the deference between faculitative aerobic and faculitative anaerobic bacteria?". 
  3. Microbiology (3rd ed.). Wm. C. Brown Publishers. 1996. pp. 130–131. ISBN 0-697-29390-4. 
  4. Ryan KJ, ed (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. pp. 261–271, 273–296. ISBN 0-8385-8529-9. 
  5. Singleton P (1999). Bacteria in Biology, Biotechnology and Medicine (5th ed.). Wiley. pp. 444–454. ISBN 0-471-98880-4. 
  6. The Fungi (2nd ed.). Academic Press. 2001. pp. 85–105. ISBN 0-12-738446-4. 
  7. Schöttler, U. (November 30, 1979). "On the Anaerobic Metabolism of Three Species of Nereis (Annelida)". Marine Ecology Progress Series 1: 249–54. doi:10.3354/meps001249. ISSN 1616-1599. Retrieved February 14, 2010. 

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