Expert: John Locke - 3/8/2008

Question
What is the difference between chemoautotrophs and chemoheterotrophs and between photoautotrophs and photoheterotrophs?
Thank you

Answer
Thanks for using AllExperts, David.

All organisms require energy and carbon from the environment to survive, bacteria included. Energy is required for the vast majority of processes that organisms carry out; carbon is the building block for the structure of living things. These four terms refer to the methods by which bacteria obtain their energy and carbon compounds: the photo/chemo prefix describes whether the bacteria use carbon dioxide (as part of photosynythesis) or organic compounds for their carbon source, respectively. The  auto/hetero prefix refers to whether the bacteria use sunlight (as part of photosynthesis) or inorganic chemicals as their energy source, respectively. That gives us four possible combinations:

Photoautotrophs: Bacteria that use sunlight as their energy source and carbon dioxide (as part of photosynthesis) as their carbon source. These bacteria thus obtain all their nourishment through photosynthesis.

Photoheterotrophs: Bacteria that use sunlight as their energy source and organic compounds from the environment as their carbon source.

Chemoautotrophs: Bacteria that use inorganic chemical reactions to provide energy and carbon dioxide as their carbon source.

Chemoheterotrophs: Bacteria that use inorganic chemical reactions to provide energy and organic compounds as their carbon source. These bacteria don't provide for any of their nourishment through photosynthesis.

There is a flowchart that summarizes these divisions here:

http://en.wikipedia.org/wiki/Autotroph

Good luck!