Table of Contents
- Definition
- Examples
- Significance of Facultative Anaerobes
- Facultative Anaerobes vs Obligate Anaerobes
- Frequently Asked Questions (FAQs)
Definition
The process of respiration involves the use of oxygen and the release of carbon dioxide, water, and energy as byproducts. Oxygen is necessary for the combustion reaction. However, some cells exist in environments with or without oxygen. While some of these species are facultative anaerobes, others must be in anaerobic conditions to survive. In either scenario, every living thing still has the biochemical machinery to oxidise glucose in a limited way without oxygen. This process of converting glucose into pyruvic acid is known as glycolysis.
The most adaptable creatures that can live with and without molecular oxygen are facultative anaerobic organisms. When present in an oxygen-rich environment, these organisms (often bacteria, archaea, or some eukaryotes) produce adenosine triphosphate (ATP) by aerobic respiration. However, in a low-oxygen environment, these organisms are capable of using fermentation or anaerobic respiration to obtain the energy they need to survive.
Examples
The most common categories of facultative anaerobes are as follows:
- The natural flora of the human body includes E. Coli. It is mainly found in the large intestine of humans and other vertebrates.
- A facultative anaerobe known as B. anthracis produces a potent exotoxin that can result in respiratory failure, nervous system discomfort, anoxia, or even death. A biological weapon has been made out of this facultative anaerobe.
- The most common facultative anaerobe is yeast. To produce alcoholic beverages (like wine and beer) and to make bread, yeast is frequently used.
- Multicellular, facultatively anaerobic molluscs are called mussels. Due to tide changes, mussels are subjected to both aerobic and anaerobic conditions. These organisms have developed into facultative beings that can live for days without oxygen from the environment.
Significance of Facultative Anaerobes
Facultative anaerobes can endure unfavourable conditions, that is, environments that lack oxygen. These organisms use different substrates for metabolism, such as iron, nitrogen, and sulphur, which have all been involved in various biogeochemical cycles on earth that have aided in the evolution of life. Thus, these organisms have been essential for maintaining and sustaining the world’s supply of the three necessary components of life—carbon, nitrogen, and sulphur—and for breaking down the tenacious molecules.
The treatment of wastewater and effluents, the commercialization of biofuel, and soil remediation all involve using facultative anaerobes. Due to their capability to reduce atmospheric carbon dioxide, these organisms have drawn significant attention. As a result, they are being explored as a substrate for converting waste gases into minerals, chemicals, and biofuels.
Currently, facultative anaerobes are used to carry out most of the fermentation operations in industrial applications (such as manufacturing ethanol and lactic acid). However, some facultative anaerobes have the potential to be infectious and harmful. Enterobacteriaceae (e.g. Escherichia coli) and the Streptococcus species are the most prevalent pathogenic facultative anaerobes.
Facultative Anaerobes vs Obligate Anaerobes
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Facultative Anaerobes |
Obligate Anaerobes |
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These organisms are extremely adaptive and can change from an aerobic to an anaerobic metabolic mode, or vice versa, to survive both in the presence of oxygen and in the absence of it. |
To survive, these organisms require a completely anaerobic environment, or one with no oxygen, as their name “Obligate” suggests. The term “obligate” denotes “strictly” or “necessarily.” |
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They are not killed by oxygen and can exist in both the presence and absence of molecular oxygen. |
The presence of molecular oxygen makes it impossible for these species to survive; oxygen is harmful to them. |
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These creatures breathe either aerobically, anaerobically, or by fermentation. |
These organisms either engage in anaerobic or fermentation respiration. |
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Superoxide dismutase is an abundant enzyme in facultative anaerobes. |
Superoxide dismutase enzyme is either absent or present in minimal amounts. |
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Some of the bacteria that grow facultatively include Escherichia coli, Streptococcus spp., Staphylococcus spp., Listeria, Salmonella, and Shewanella oneidensis. |
Examples include Veillonella, Clostridium, Peptostreptococcus, Fusobacterium, Prevotella, Porphyromonas, and Bacteroides. |
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