Definition: one-celled; some absorb food from their surroundings; some are photosynthetic; some are chemosynthesic; many are found in extremely harsh environments including salt ponds hot springs swamps and deep-sea hydrothermal vents.

Three different types of archaebacteria: Methanogens, this type of archaebacteria live in oxygen free environments and they produce methane gases. Halophiles, halophiles live in water with very high concentration of salt. Thermophiles, these type of bacteria live in hot areas and very hot and acidic sulfur springs.

Archaebacteria and bacteria are generally the same size and shape but sometimes archaebacteria are shaped differently.

The suffix "Phile" means love for something so halophile means the love for salt because halo means salt and thermophile means the love for heat because thermo means heat.

The suffix "gen" means it produces something so methanogen means it produces a gas called methane.

The most primitive group, the archaebacteria, are today restricted to marginal habitats such as hot springs or areas of low oxygen concentration.

Species:

Methanobrevibacter

Halobacterium salinarum

Thermococcus litoralis

Thermoplasma volcanium

Sulfolobus acidocaldarius