What is the Difference Between Aerobic and Anaerobic Bacteria with Definition and Examples
Anaerobic bacteria are microorganisms that survive in the absence of oxygen. They cannot tolerate oxygen at all and will die if exposed to an environment that has a high quantity of oxygen. Anaerobic metabolism involves organic or inorganic redox reactions, fermentation reactions and anaerobic reaction which produces highly volatile fatty acids and gaseous molecules such as methane and alcohol.
Anaerobic Bacteria can be Classified Into:
Facultative Anaerobes: These anaerobes are the most versatile and they preferentially utilize oxygen as a terminal electron acceptor. They can also metabolize in the absence of oxygen by reducing other compounds. Much more usable energy, in the form of high-energy phosphate, is obtained when a molecule of glucose is completely catabolized to CO2 and H2O in the presence of O2 (38 molecules of ATP) than when it is only partially catabolized by a fermentative process in the absence of O2 (2 molecules of ATP).
Microaerophilic Anaerobes: These types of anaerobes can only proliferate in low concentrations of oxygen (2 to 10%) or in an atmosphere with high CO2 concentration i.e. 10% of CO2.
Obligate Anaerobes: Obligate anaerobes are completely incapable of aerobic metabolism but they are variably tolerant to oxygen. These organisms can be categorized into three different classes. These are:
Strict: Tolerance level of only ≤ 0.5% of Oxygen
Moderate: Tolerance level of 2-8 % of Oxygen
Aero Tolerant Anaerobes: These obligate anaerobes can tolerate atmospheric oxygen for a limited time. These anaerobic bacteria require oxygen to live.
Anaerobic Bacteria Examples
Bacteroides, Bifidobacterium, Fusobacterium, Porphyromonas, Prevotella, Actinomyces,
Propionibacterium, Clostridia, etc are the examples of such bacteria. Anaerobic bacteria are medically significant as they cause many infections in the human body. For example, various species of Clostridia can cause food poisoning, soft-tissue infection, etc, whereas Actinomyces can cause head, neck, abdominal and pelvic infections.
What are Aerobic Bacteria?
As the name suggests, aerobic bacteria come under the class of microorganisms which grow and survive in an oxygenated environment, in short, aerobic bacteria require oxygen to live. Aerobic bacteria are critical for biological decomposition. The presence of oxygen hastens the decomposition of hydrocarbons. This type of decomposition can be seen on the forest floor, where aerobes are decomposing leaves and other organic debris. Organic material decomposition is an aerobic process. As the amount of carbon dioxide in the atmosphere rises, the rate of decomposition slows. Surprisingly, aerobic composting does not produce a foul odour. It's critical to know what the anaerobic process is before proceeding. A process that takes place in the presence of oxygen is known as an aerobic process.
Aerobic Bacteria can be Classified Into:
Obligate Aerobes: Obligate aerobes need oxygen to survive. "organisms that require oxygen to thrive and survive." So, in biology, obligatory aerobes are creatures that can only grow and survive in the presence of oxygen since they get their energy through aerobic respiration with oxygen. The process of oxidative phosphorylation in oxidative (aerobic) respiration, which uses oxygen as the terminal electron acceptor, provides energy to these organisms.
They utilize atmospheric oxygen to oxidize substrates such as sugar and fats to generate energy and carry out metabolic activities. Aerobic microorganisms use glycolysis, the Krebs TCA cycle, and an electron transport chain with oxygen as the final electron acceptor. The enzymes used are catalase, peroxidase, and superoxide dismutase.
Facultative Aerobes: The aerobes use oxygen when it is available but are not solely reliant on it. They have anaerobic methods of energy production.
Microaerophiles: They require oxygen for energy production. However, a high concentration of atmospheric oxygen is harmful to them. They use fermentation reactions for energy and do not have an electron transport system.
Aerotolerant Aerobes: They do not use oxygen for metabolic activities and are not harmed by it. They lack all three enzymes needed to break down oxygen.
Aerobic Bacteria Examples: Some examples of aerobic bacteria are Nocardia sp. Pseudomonas aeruginosa, E. Coli, Citrobacter, Klebsiella, Proteus, Salmonella, Achromobacter Mycobacterium tuberculosis etc.
Differentiate Between Aerobic and Anaerobic Bacteria
In this section, we will discuss the differences between aerobic and anaerobic bacteria.
Aerobic and Anaerobic Bacteria List:
Aerobic Bacteria List:
E. Coli
Citrobacter
Klebsiella
Proteus
Salmonella
Achromobacter
Anaerobic Bacteria List:
Actinomyces
Bifidobacterium
Fusobacterium
Propionibacterium
Clostridium
Bacteroides
Prevotella
FAQs on Difference Between Aerobic and Anaerobic Bacteria in Detail
1. What is the difference between aerobic and anaerobic bacteria?
The main difference between aerobic bacteria and anaerobic bacteria is that aerobic bacteria require oxygen for growth, while anaerobic bacteria grow without oxygen.
- Aerobic bacteria use oxygen for cellular respiration and energy production.
- Anaerobic bacteria either cannot tolerate oxygen or do not need it for metabolism.
- This difference affects their habitat, metabolism, and survival conditions.
2. What are aerobic bacteria?
Aerobic bacteria are microorganisms that require oxygen to carry out aerobic respiration and produce energy.
- They use oxygen as the final electron acceptor in the electron transport chain.
- They produce more ATP compared to anaerobic respiration.
- Common examples include Mycobacterium tuberculosis and Nocardia.
3. What are anaerobic bacteria?
Anaerobic bacteria are microorganisms that grow in the absence of oxygen and may even be harmed by it.
- They obtain energy through anaerobic respiration or fermentation.
- Some are obligate anaerobes and cannot survive in oxygen.
- Examples include Clostridium botulinum and Bacteroides species.
4. How do aerobic bacteria obtain energy?
Aerobic bacteria obtain energy through aerobic respiration, which uses oxygen to completely break down glucose.
- Glucose undergoes glycolysis in the cytoplasm.
- Pyruvate enters the Krebs cycle in the cytoplasm (prokaryotes lack mitochondria).
- The electron transport chain uses oxygen to generate large amounts of ATP.
5. How do anaerobic bacteria obtain energy?
Anaerobic bacteria obtain energy through anaerobic respiration or fermentation without using oxygen.
- In anaerobic respiration, substances like nitrate or sulfate act as final electron acceptors.
- In fermentation, glucose is partially broken down to produce organic acids or alcohol.
- This process produces less ATP compared to aerobic respiration.
6. What are obligate and facultative anaerobes?
Obligate anaerobes cannot survive in oxygen, whereas facultative anaerobes can grow with or without oxygen.
- Obligate anaerobes are harmed or killed by oxygen (e.g., Clostridium).
- Facultative anaerobes prefer oxygen but can switch to fermentation if oxygen is absent (e.g., Escherichia coli).
- This flexibility provides survival advantage in changing environments.
7. Can anaerobic bacteria survive in oxygen?
Most obligate anaerobic bacteria cannot survive in oxygen because they lack enzymes that neutralize toxic oxygen byproducts.
- They lack protective enzymes like catalase and superoxide dismutase.
- Oxygen exposure leads to accumulation of harmful reactive oxygen species.
- However, facultative anaerobes can tolerate and use oxygen when available.
8. Where are aerobic and anaerobic bacteria commonly found?
Aerobic bacteria are found in oxygen-rich environments, while anaerobic bacteria thrive in oxygen-free habitats.
- Aerobic bacteria: soil surface, water, air, and human lungs.
- Anaerobic bacteria: deep wounds, sediments, sewage, and the human intestine.
- Their distribution depends on oxygen availability and metabolic adaptation.
9. What are some examples of aerobic and anaerobic bacteria?
Examples of aerobic bacteria include Mycobacterium tuberculosis, while examples of anaerobic bacteria include Clostridium tetani.
- Aerobic bacteria: Mycobacterium, Nocardia.
- Obligate anaerobes: Clostridium, Bacteroides.
- Facultative anaerobes: Escherichia coli, Salmonella.
10. Why is the difference between aerobic and anaerobic bacteria important in medicine?
The difference between aerobic and anaerobic bacteria is important in medicine because it determines infection type, diagnosis, and treatment strategy.
- Some infections occur in oxygen-poor tissues and involve anaerobic bacteria.
- Laboratory culture methods differ based on oxygen requirement.
- Antibiotic selection may vary depending on bacterial metabolism.
