A group of living things
Archaea
Archaea
Bacteria look-alikes that turned out to be deep family
Its members' last common ancestor lived about 3.5 billion years ago.
You are part of this group. See how.
Most of these tiny microbes look like bacteria under the microscope, yet their genes tell a quite different story. They form their own deep branch of life, separate from bacteria. In a big surprise, our own group — animals, plants, fungi and people — grew out from inside this branch.
Each one is a single cell with no nucleus, far too small to see without a microscope. Cells come in many shapes: round balls, short rods like jelly beans, triangles, and even flat squares like postage stamps. Some are bare, while others swim with one or more hair-like tails usually sprouting from one side.
They live almost everywhere, from boiling springs and salty pink lakes to open seas, soils and animal guts. Single cells are colourless or pale grey, but crowds paint salt lakes pink, red and purple and hot springs in rainbow mats. Only some kinds make methane gas in places with no air.
Found by reading genes
In the late 1970s Carl Woese and colleagues compared genes and found these microbes formed a separate group, first called Archaebacteria.
At least one in five sea microbes
Surveys in the early 1990s found at least about 20 per cent of microbes in the sea are from this group, overturning the old idea they lived only in extreme places.
No known troublemakers
No known kind causes disease in people, animals or plants, even though they live naturally in and on most people.