What role do bacteria and archaea play in the environment?
Prokaryotes play a wide range of roles in the environment. Metabolically, bacteria and archaea may be photoautotrophic, chemoautotrophic, photoheterotrophic or chemoheterotrophic. This means they may either create or ingest glucose as an organic carbon source, and they can do so using energy from either the sun or other inorganic chemicals. Bacteria and archaea therefore may be producers or consumers in an environment.
Prokaryotes may also be a part of different relationships in the environment. Some are mutualistic, such as when microorganisms break down food in the stomachs of animals. Others are parasitic, like in the case of bacterial disease. Heterotrophs partake in predation or herbivory and almost all bacteria and archaea compete for resources.
Most important, however, is the role of bacteria in nutrient cycles. Almost all of these are regulated by these prokaryotes. Without their presence, nutrient flow would cease. Atmospheric nitrogen, for example, must be fixed by bacteria into an organic form for plants to be able to use it.