Primary Sources of Reducing Equivalents
Organotrophs: Organic compounds are used as electron donor.
Lithotrophs: Inorganic compounds are used as electron donor.
The electrons from reducing equivalents are needed by both, phototrophs and chemotrophs, to keep running reduction-oxidation reactions that transfer energy. The electron donors are taken up from the environment.
Organotrophic organisms are often also heterotrophic, using organic compounds as sources of electrons and carbon at the same time. Similarly, lithotrophic organisms are often also autotrophic, using inorganic sources of electrons and CO2 as inorganic carbon source.
Some lithotrophic bacteria can utilize diverse sources of electrons, depending on availability of possible donors.
Read more about this topic: Primary Nutritional Groups
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