Question

What are facultative anaerobes?

Answer 1

Hint: Any lifeform that does not demand molecular oxygen to develop is known as an anaerobic organism or anaerobe. If free oxygen is provided, it may respond adversely or possibly perish. Anaerobes, unlike aerobes that necessitate oxygen to grow, can consume a range of distinct molecules during metabolism.

Complete answer
The most versatile organisms are facultative anaerobes, which can thrive both in the presence and deprivation of molecular oxygen. When present in an oxygen-rich environment, these organisms (generally Bacteria or Archaea or certain eukaryotes) yield adenosine triphosphate (ATP) through aerobic cellular respiration; however, in an oxygen inhibited surrounding, these organisms can obtain energy for sustenance via anaerobic respiration or fermentation.
Substitute electron acceptors in the electron transport chain, which is the primary chemical mechanism involved in the production of ATP during cellular respiration and photosynthesis, have developed in facultative anaerobe lifeforms to adapt to harsh environmental circumstances. When placed in an oxygen-depleted environment, facultative anaerobes can use nitrate, nitrite, fumarate, elemental Sulphur, or metal ions like iron or manganese as electron acceptors.

Additional information:
Staphylococcus spp., Escherichia coli, Salmonella, Listeria spp, Shewanella oneidensis, and Yersinia pestis are examples of facultatively anaerobic bacteria. Many eukaryotes, notably fungi like Saccharomyces cerevisiae and aquatic invertebrates like nereid polychaetes, are facultative anaerobes.

Note:
The organisms which can survive in both oxygenated as well as the deoxygenated environment are known as facultative anaerobes. If oxygen is available, a facultative anaerobe produces ATP through aerobic respiration, but it can shift to fermentation if oxygen is not present.