In the late 1970s, a new branch was added to the tree of life, and archaea joined bacteria and eukarya, as domain classifications. Archaea and bacteria are both simple forms of cells called ...

Scanning electron micrograph of Methanobrevibacter smithii DSM 861 (=PS T), Methanobrevibacter smithii DSM 2375 (=ALI), Methanobrevibacter smithii GRAZ-2 and WWM1085. Credit: International Journal of ...