Sulfolobus archaea. Coloured transmission electron micrograph (TEM) of a section through a Sulfolobus sp. archaeon. Archaea are single-celled organisms that are similar to bacteria, but also have characteristics of higher organisms, as well as unique characteristics (such as the structure of their cell wall, yellow). Sulfolobus is an extremophile that is found in hot springs and thrives in acidic and sulphur-rich environments. It experiences optimal growth at 80 degrees Celsius Magnification: x10,8000 when printed 10 centimetres tall.