State two economically important uses of: (a) heterotrophic bacteria (b) archaebacteria

Two economically important uses are:

(a) Heterotrophic bacteria are used in the production of products such as antibiotics and in processes like the fermentation of foods (e.g., curd formation from milk).

(b) Archaebacteria are important for biogas production, as methanogens (a type of archaebacteria) present in the guts of ruminants produce methane from dung, which can be harnessed as an energy source.