(a) Use of heterotrophic bacteria :
(i) They helps in making curd from milk.
(ii) They are helpful in nitrogen fixation in roots of leguminous plants.
(b) Uses of archaebacteria :
(i) They lives in the guts of several ruminant animals such as cow and buffaloes and helps in their digestion.
(ii) They help in the production of bio-gas such as methane