Question

What is the difference between a photoheterotroph and chemoheterotroph, and what are examples of these?

Answer 1

When classifying organisms like this, you are looking for two main descriptors of their lifestyle: how they get their energy and how they get their carbon. A phototroph is an organism that acquires its energy through harvesting photons. A chemotroph harvests energy from chemical bonds.

The term heterotroph is used to describe organisms that acquire carbon from organic substances (namely from other organisms). An autotroph is an organism that has the ability to fix atmospheric carbon CO2 into an organic form.

When you combine these terms, you get a word that describes how an organism harvests energy and carbon. So, a chemoheterotroph is an organism that acquires energy from chemical bonds, and uses acquires organic carbon from an external source (usually, in this case, the energy and carbon come from the same source, e.g., glucose). A photoheterotroph is an organism that gains energy from photons but gains carbon from an external organic source.

Most bacteria, fungi, and animals can easily be described as a chemoheterotroph. A specific bacteria would be Pseudomonas aeruginosa.

Photoheterotrophs would only be found in the prokaryote domains. An example would be Heliobacter. Just to note, there are very few genera of photoheterotrophs. Remember, they gain most of their energy from light (photons), and their carbon from an external organic source (i.e., they do not fix carbon).

Basically, photoheterotrophs get energy from light and chemoheterotrophs get energy from breaking chemical bonds.

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