The key difference between Aerobic and Anaerobic Microorganisms is the requirement of oxygen for the survival aerobic microorganisms while it is not for the anaerobic microorganisms. That is, the aerobic microorganisms require oxygen as their final electron acceptor during the aerobic respiration while anaerobic microorganisms do not require oxygen for their cellular respiration.
The response to oxygen is the basis for classification of the microorganisms as aerobic and anaerobic. Because of this, these microorganisms possess different characteristics to perform their functions during cellular respiration. Therefore, aerobic microbes undergo aerobic respiration, whereas anaerobic microbes undergo anaerobic respiration.
CONTENTS
1. Overview and Key Difference
2. What are Aerobic Microorganisms
3. What are Anaerobic Microorganisms
4. Similarities Between Aerobic and Anaerobic Microorganisms
5. Side by Side Comparison – Aerobic and Anaerobic Microorganisms in Tabular Form
6. Summary
What are Aerobic Microorganisms?
Aerobic Microorganisms are a group of microorganisms in which oxygen acts as the final electron acceptor in cellular respiration. Therefore, these microbes require molecular oxygen for its survival. They oxidize monosaccharides such as glucose in the presence of oxygen. The main processes that generate energy in aerobes are glycolysis, followed by the Krebs cycle and the electron transport chain. As oxygen levels are not toxic to these microorganisms, they grow well in oxygenated media. And thus, they are obligate aerobes (Bacillus sp,)
Figure 01: Aerobic Bacteria
Classification
Microaerophilic microbes, aerotolerant microorganisms, and facultative anaerobes are the three classifications of aerobes. The basis of this classification is the toxicity levels of oxygen to these microorganisms.
- Microaerophilic microorganisms – survive low concentrations (about 10%) of oxygen (Helicobacter pylori is an example microorganism).
- Aerotolerant microorganisms – They do not require oxygen for its survival. In contrast, the presence of oxygen does not harm the microbes (Lactobacillus sp is an example)
- Facultative anaerobes – These microbes can survive in both the presence and absence of oxygen. (Escherichia coli is a facultative anaerobe)
What are Anaerobic Microorganisms?
Anaerobic microorganisms are obligatory anaerobes. They do not use oxygen as their final electron acceptor. Instead, they use substrates such as nitrogen, methane, ferric, manganese, cobalt or sulfur as their final electron acceptors. Organisms such as Clostridium sp belong to this category. Furthermore, Anaerobes undergo fermentation to produce energy. There are two main types of anaerobic fermentation processes; lactic acid fermentation and ethanol fermentation. Through these processes, anaerobes produce energy (ATP), which is necessary for their survival.
Figure 02: Anaerobic Bacteria
Anaerobic microorganisms do not survive in the Oxygen-rich environment because oxygen is toxic to obligate anaerobes. In contrast, excess levels of oxygen do not harm facultative anaerobes.
What are the Similarities Between Aerobic and Anaerobic Microorganisms?
- By nature, both aerobic and anaerobic microorganisms are prokaryotic.
- Both these microbes undergo glycolysis, which is the first step of cellular respiration.
- Aerobic and anaerobic consist of pathogenic disease-causing microorganisms.
- Both types consist of industrially important microbes.
What is the Difference Between Aerobic and Anaerobic Microorganisms?
Aerobic vs Anaerobic Microorganisms |
|
| Aerobic microorganisms are the organisms that require oxygen for their survival since it is the final electron acceptor of their cellular respiration. | Anaerobic microorganisms are the microbes that do not require oxygen for their cellular respiration. |
| Final Electron Acceptors | |
| Oxygen is the final electron acceptor of aerobic microorganisms. | Sulfur, Nitrogen, Methane, Sulfur, Ferric are the final electron acceptors of anaerobic microorganisms. |
| Processes Involved in Cellular Respiration | |
| Glycolysis, Krebs cycle and electron transport chain are the three stages of cellular respiration. | Glycolysis and fermentation are the stages of anaerobic respiration. |
| Types | |
| Obligate, facultative, aerotolerant, and microaerophilic | Obligate and facultative anaerobes |
| Required Media for Microbial Growth | |
| Obligate aerobes require oxygen-rich media. | Obligate anaerobes require media devoid of oxygen. |
| Toxicity of Oxygen | |
| Aerobes are non-toxic to oxygen. | Anaerobic microorganisms are highly toxic to oxygen. |
| Presence of Oxygen Detoxifying Enzymes | |
| Present in aerobes. | Absent in anaerobes. |
| Efficiency of Energy Production | |
| Energy production is high in aerobes. | Energy production is low in anaerobes. |
| Examples | |
| Bacillus spp, Pseudomonas aeruginosa , Mycobacterium tuberculosis, etc. | Actinomyces, Bacteroides, Propionibacterium, Veillonella, Peptostreptococcus, Porphyromonas, Clostridium spp etc. |
Summary – Aerobic vs Anaerobic Microorganisms
Aerobic and anaerobic microorganisms differ in the final electron acceptor. Aerobes utilize molecular oxygen as the final electron acceptor. In contrast, Anaerobes use substances such as nitrates, sulfur, and methane as the final electron acceptor. Therefore, the key difference between aerobic and anaerobic microorganisms is the type of final electron acceptor they use during cellular respiration.
Reference:
1.Hentges, David J. “Anaerobes: General Characteristics.” Medical Microbiology. 4th Edition., U.S. National Library of Medicine, 1 Jan. 1996. Available here
2.Smith, Charles G., and Marvin J. Johnson. “AERATION REQUIREMENTS FOR THE GROWTH OF AEROBIC MICROORGANISMS.” Journal of Bacteriology, U.S. National Library of Medicine, Sept. 1954. Available here
Image Courtesy:
1.’Hepatocytes – Production and distribution’ (Public Domain) via Pixnio
2.’Anaerobic bacteria’By Mclovinx – Own work, (CC BY-SA 4.0) via Commons Wikimedia