Archaebacteria are different from other bacteria in having different cell wall structure. Archaebacteria is unique since they live in some of the harshest environments such as hot springs (thermoacdiophiles), extremely salty areas (halophiles), too marshy areas (methanogens). Methanogens can convert CO2, methanol, formic acid into methane so are called methanogens. They are abundantly found in the cattle yard because they are present in excreta of cattle. They are found in the biogas plant and are a subgroup of archaebacteria. Example: Methanobacterium.