Primary nutritional groups are groups of organisms, divided according to the sources of energy and carbon, needed for living, growth and reproduction. The sources of energy can be light and organic or inorganic compounds; the sources of carbon can be of organic or inorganic origin. 
The terms aerobic respiration, anaerobic respiration and fermentation do not refer to primary nutritional groups, but simply reflect the different use of possible electron acceptors in particular organisms, such as O2 in aerobic respiration, or NO3-, SO42- or fumarate in anaerobic respiration, or various metabolic intermediates in fermentation. Because all ATP-generating steps in fermentation involve modifications of metabolic intermediates instead of the use of an electron transport chain fermentation is often referred to as substrate-level phosphorylation.
Primary sources of energy
Phototrophs: Light is absorbed in photo receptors and transformed into chemical energy.
Chemotrophs: Bond energy is released from a chemical compound.
The freed energy is stored as potential energy in ATP, carbohydrates, lipids or proteins. Eventually, the energy is used for life processes as moving, growth and reproduction.
Some bacteria can alternate phototrophy and chemotrophy, depending on availability of light.
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.
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