Chemoautotrophs are able to synthesize their own organic molecules from the fixation of carbon dioxide. The prefix "auto" refers to self and "troph" refers to feeding and identifies the ability of these organisms to produce their own source of food, or energy. The energy required for this process comes from the oxidation of inorganic molecules such as iron, sulfur or magnesium.
Chemoheterotrophs, unlike chemoautotrophs, are unable to synthesize their own organic molecules. Instead, these organisms must ingest preformed carbon molecules, such as carbohydrates and lipids, synthesized by other organisms. They do, however, still obtain energy from the oxidation of inorganic molecules like the chemoautotrophs.
The environment that these two classes of chemotrophs are found is directly related to their respective ability to produce carbon-containing molecules. Chemoautotrophs are able to thrive in very harsh environments, such as deep sea vents, due to their lack of dependence on outside sources of carbon other than carbon dioxide. Chemoheterotrophs, however, are only able to thrive in environments that are capable of sustaining other forms of life due to their dependence of these organisms for carbon sources.
Examples of chemoautotrophs include nitrogen fixing bacteria located in the soil, iron oxidizing bacteria located in the lava beds, and sulfur oxidizing bacteria located in deep sea thermal vents. Chemoheterotrophs are the most abundant type of chemotrophic organisms and include most bacteria, fungi and protozoa.