Bacteria are Earth's first life forms. They continue to dominate environmental evolution in the twentieth century. Ancient bacteria (archae) thrive in extreme environments typical of Archean (early) Earth.
Heat- and acid-loving microbes flourish in boiling muds, hot springs, deep-sea vents and ash-ejecting volcanoes. They loll in waters as hot as 110 degrees C [230 degrees F], and freeze at temperatures below 55 degrees C [131 degrees F]. Some of these bacteria find an abode in pools of concentrated sulfuric acid.
Twentieth century microbial methane makers thrive in oxygenfree sediments inside animals, and in sewage. Producing all the methane in Earth’s atmosphere, these bacteria prevent oxygen levels from reaching an explosive concentration.