Prokaryotes

Environment

Prokaryotes have diversified greatly throughout their long existence. Their metabolism is far more varied than that of eukaryotes, leading to many highly distinct types. For example, prokaryotes may obtain energy by chemosynthesis. Prokaryotes live nearly everywhere on Earth, including in environments as cold as soils in Antarctica, or as hot as undersea hydrothermal vents and land-based hot springs. Some bacteria are pathogenic, causing disease in organisms including humans. Some archaea and bacteria are extremophiles, thriving in harsh conditions, such as high temperatures (thermophiles) or high salinity (halophiles). Some archaeans are methanogens, living in anoxic environments and releasing methane. Many archaea grow as plankton in the oceans. Symbiotic prokaryotes live in or on the bodies of other organisms, including humans. Prokaryotes have high populations in the soil, in the sea, and in undersea sediments. Soil prokaryotes are still heavily undercharacterized despite their easy proximity to humans and their tremendous economic importance to agriculture.