What is the Difference Between Chemolithotrophs and Chemoautotrophs

The main difference between chemolithotrophs and chemoautotrophs is that chemolithotrophs use inorganic molecules to obtain energy whereas chemoautotrophs synthesize all organic compounds from carbon dioxide.

Chemolithotrophs and chemoautotrophs are two types of organisms that use chemical compounds to obtain energy in cellular respiration. Therefore, they use chemical energy rather than the energy from sunlight in phototrophs.

Key Areas Covered

1. What are Chemotrophs
   • Definition, Features, Importance
2. What are Chemolithotrophs
   • Definition, Features, Importance
3. What are Chemoautotrophs
   • Definition, Features, Importance
4. Similarities Between Chemolithotrophs and Chemoautotrophs
   • Outline of Common Features
5. Difference Between Chemolithotrophs and Chemoautotrophs
   • Comparison with Key Differences

Key Terms

Chemoautotrophs, Chemolithotrophs, Chemotrophs, Chemoheterotrophs

What are Chemotrophs

Chemotrophs are organisms that get energy through chemical processes known as chemosynthesis rather than photosynthesis in phototrophs. However, chemosynthesis involves the oxidation of electron donors in the environment. Moreover, there are two types of chemotrophs: chemoautotrophs and chemoheterotrophs. Chemoautotrophs produce their own food through chemosynthesis. They use chemical energy to produce carbohydrates. Meanwhile, chemoheterotrophs are unable to fix carbon to form their own organic compounds. They can be either chemolithoheterotrophs or chemoorganoheterotrophs. Here, chemolithoheterotrophs utilize inorganic electron sources such as sulfur, while chemoorganoheterotrophs, utilize organic electron sources such as carbohydrates, lipids, and proteins. Host animals and fungi are examples of chemoheterotrophs

What are Chemolithotrophs

Chemolithotrophs are organisms capable of using inorganic reduced compounds in their energy-producing reactions. This process occurs through oxidation and ATP synthesis. In addition, the majority of chemolithotrophs are chemolithoautotrophs, able to fix carbon dioxide through the Calvin cycle, a metabolic pathway in which CO2 is converted to glucose. This group of organisms includes sulfur oxidizers, nitrifying bacteria, iron oxidizers, and hydrogen oxidizers.

Figure 1: Nitrifying Bacteria in the Nitrogen Cycle

What are Chemoautotrophs

Chemoautotrophs are organisms that synthesize all necessary organic compounds from carbon dioxide. In the meanwhile, they use inorganic energy sources such as hydrogen sulfide, elemental sulfur, ferrous iron, molecular hydrogen, and ammonia or organic sources to produce energy. 

Figure 2: Deep Sea Vents

Most chemoautotrophs are extremophiles: bacteria and archaea that live in hostile environments such as deep-sea vents. These are the primary producers in these hostile environments. Some examples of chemoautotrophs include methanogens, sulfur oxidizers and reducers, nitrifiers, anammox bacteria, and thermoacidophiles.

Similarities Between Chemolithotrophs and Chemoautotroph

• Chemolithotrophs and chemoautotrophs are two types of organisms that use chemical reactions to obtain energy.
• Moreover, they obtain energy by oxidizing electron donors.
• Here, electron donors can be either organic compounds in chemoorganotrophs or inorganic molecules in chemolithotrophs.
• The carbon source of both chemolithotrophs and chemoautotrophs is carbon dioxide.

Difference Between Chemolithotrophs and Chemoautotrophs

Definition

Chemolithotrophs refer to organisms that use chemical energy from inorganic compounds to synthesize all organic compounds, while chemoautotrophs refer to an organism, typically a bacterium, which derives energy from the oxidation of inorganic and organic compounds.

Significance

Usually, chemolithotrophs use inorganic molecules as their final electron acceptor while chemoautotrophs use oxygen as their final electron acceptor in the electron transport chain.

Occurrence

Chemolithotrophs are sulfur oxidizers, nitrifying bacteria, iron oxidizers, and hydrogen oxidizers while chemoautotrophs are extremophiles: bacteria and archaea that live in hostile environments such as deep-sea vents.

Conclusion

In brief, chemolithotrophs are organisms, mainly bacteria, that use chemical energy from inorganic, reduced compounds to synthesize the organic compounds of the organisms. In contrast, chemoautotrophs are organisms that get energy from organic and inorganic compounds to produce their organic molecules from carbon dioxide. Chemolithotrophs are sulfur oxidizers and nitrifying bacteria while chemoautotrophs are extremophiles that live in hostile environments. Therefore, the main difference between chemolithotrophs and chemoautotrophs is their final electron acceptor.

References:

1. Chemotroph. Biology Articles, Tutorials & Dictionary Online. Retrieved September 17, 2022.
2. Wikimedia Foundation. (2022, September 11). Lithotroph. Wikipedia. Retrieved September 17, 2022.

Image Courtesy:

1. “Nitrogen Cycle” By Johann Dréo – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Blacksmoker in Atlantic Ocean ” By P. Rona – Own Work (Public Domain) via Commons Wikimedia