The primitive prokaryotes responsible for the production of biogas from the dung of ruminant animals, include the

Methanogens are a group of archaebacteria responsible for the production of biogas from the dung of ruminant animals. They are present in marshy areas and in rumen of cattle.

(2) Eubacteria are those that have peptidoglycan or mureins in their cell wall. These are not involved in methane
production. 

(3) Bacteria or archaebacteria are present in salty areas and they are called halophiles.

(4) Thermoacidophiles are those archaebacteria present in hot springs.