What is the Difference Between Auxotroph and Prototroph

The main difference between auxotroph and prototroph is that auxotroph is unable to produce a particular organic compound needed for its growth whereas prototroph is capable of producing all the organic compounds it requires for its growth.

Auxotrophs and prototrophs are two types of organisms characterized by their ability to synthesize organic compounds required for their growth. Auxotrophs can only grow in a minimal medium when the nutrient that is lacking in that auxotrophs is present in the medium.

Key Areas Covered

1. What is Auxotroph
   • Definition, Features, Importance
2. What is Prototroph
   • Definition, Features, Importance
3. Similarities Between Auxotroph and Prototroph
   • Outline of Common Features
4. Difference Between Auxotroph and Prototroph
   • Comparison of Key Differences

Key Terms

Auxotroph, Prototroph

What is Auxotroph

Auxotroph is an organism that is unable to synthesize a particular organic compound required for its growth. It is a mutant type. That means an auxotroph carries a mutation that renders it unable to synthesize an essential compound. For instance, uracil auxotroph, which is a yeast mutant, has inactivated its uracil synthesis pathway. Thus, it cannot synthesize uracil and will only grow where uracil is available.

Figure 1: Arginine Auxotrophs

Furthermore, prototrophs are the opposite of auxotrophs, producing all essential organic compounds inside the cell. Unlike uracil auxotrophs, prototrophs synthesize uracil. Therefore, prototrophs are a wild-type strain but, uracil auxotroph is a mutant. Moreover, auxotrophic genetic markers are often helpful in molecular genetics. In addition, autotrophy is important in the incorporation of unnatural amino acids into the proteome of an organism.

Normally, auxotrophs do not grow in the minimal medium. But, when the nutrient that is not present in the auxotroph is added to the minimal medium,  the auxotroph can survive.

What is Prototroph

Prototroph is an organism that is capable of producing all the necessary organic compounds inside the organism. Usually, a prototrophic organism is known as the wild-type as its auxotrophic organism lack the synthesis pathway of certain organic compounds. Prototrophs are self-sufficient producers of all required metabolites (e.g. amino acids, lipids, cofactors), while auxotrophs are required to be in a medium with the metabolite that they cannot produce.

Figure 2: Bacterial Culture

For example, when a cell is methionine auxotrophic, it would need to be on a medium containing methionine, or else it would not be able to replicate. This is because it is unable to produce its own methionine (methionine auxotroph). However, a prototroph or a methionine prototrophic cell would be able to function and replicate on a medium with or without methionine.

Similarities Between Auxotroph and Prototroph

• Auxotrophs and prototrophs are two types of organisms that are characterized by the requirement of organic compounds for their growth.
• Usually, they are microorganisms.

Difference Between Auxotroph and Prototroph

Definition

Auxotroph refers to any microorganism that has lost the ability to synthesize an organic compound required for its growth, usually as a result of mutation, while prototroph refers to any microorganism that can synthesize its nutrients from inorganic material.

Genetics

Auxotroph is the mutant organism while prototroph is the wild-type organism.

Minimal Media

Moreover, auxotroph does not grow in minimal media while prototroph grows in minimal media.

Conclusion

In brief, an auxotroph is a mutant organism that cannot synthesize a particular organic compound required for its growth. However, a prototroph is a wild-type organism that can synthesize all the organic compounds required for its growth. In the minimal medium, prototrophs can grow, but auxotrophs cannot. However, auxotrophs survive when the nutrient they lack is present in the minimal medium. Therefore, the main difference between auxotroph and prototroph is their ability to produce organic compounds.

References:

1. Wikimedia Foundation. (2021, December 6). Auxotrophy. Wikipedia. Retrieved August 29, 2022

Image Courtesy:

1. “AUXOTROPHY Fig 1Replica plating growth comparison between Arg- Auxotroph and Prototroph” By Akardoust – Own Work (CC BY-SA 4.0) via Commons Wikimedia
2. “Bacterial culture” By Joydeep – Own Work (CC BY-SA 3.0) via Commons Wikimedia