Difference Between Aerobic and Anaerobic Bacteria

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:

1. Strict: Tolerance level of only ≤ 0.5% of Oxygen

2. Moderate: Tolerance level of 2-8 % of Oxygen

3. 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