Heterotrophic bacteria eat other organisms and absorb dead organic material, while autotrophic bacteria create their own food, according to Medical News Today. Some autotrophs feed themselves through photosynthesis, while others perform chemosynthesis.
Most heterotrophs are saprobes, which means they consume dead organic material like decomposing flesh, says Medical News Today. Some of these parasitic bacteria feed by killing their hosts, while others help their hosts. Autotrophs produce their own food through photosynthesis or chemosynthesis. Photosynthesis involves the use of sunlight, carbon dioxide and water to create food. Autotrophic bacteria that synthesize their food using sunlight are known as photoautotrophs. Examples of this type of bacteria are cyanobacteria, which contribute to the production of oxygen for the atmosphere. Some photoautotrophs do not create oxygen, such as green sulfur bacteria, purple sulfur bacteria and heliobacteria.
Medical News Today explains that chemoautotrophs manufacture their own food through chemosynthesis, the process of using water, carbon dioxide and other chemicals as ammonia to synthesize food. Some of the chemicals they use for nutrition are sulfur, phosphorus, nitrogen, vitamins and metallic elements, such as calcium, potassium and sodium. Chemoautotrophs are also called nitrogen fixers, and they are typically found in ocean vents and legumes, such as peanuts, beans, peas and clover.