1. How the organism obtains carbon for synthesising cell mass:
autotrophic – carbon is obtained from carbon dioxide (CO2) heterotrophic – carbon is obtained from organic compounds mixotrophic – carbon is obtained from both organic compounds and by fixing carbon dioxide
2. How the organism obtains reducing equivalents used either in energy conservation or in biosynthetic reactions:
lithotrophic – reducing equivalents are obtained from inorganic compounds organotrophic – reducing equivalents are obtained from organic compounds
3. How the organism obtains energy for living and growing:
chemotrophic – energy is obtained from external chemical compounds phototrophic – energy is obtained from light
In practice, these terms are almost freely combined. Typical examples are as follows:
chemolithoautotrophs obtain energy from the oxidation of inorganic compounds and carbon from the fixation of carbon dioxide. Examples: Nitrifying bacteria, Sulfur-oxidizing bacteria, Iron-oxidizing bacteria, Knallgas-bacteria photolithoautotrophs obtain energy from light and carbon from the fixation of carbon dioxide, using reducing equivalents from inorganic compounds. Examples: Cyanobacteria (water (H2O) as reducing equivalent donor), Chlorobiaceae, Chromatiaceae (hydrogen sulfide (H2S) as reducing equivalent donor), Chloroflexus (hydrogen (H2) as reducing...