State two economical

(a) Heterotrophic bacteria: those bacteria that cannot synthesize their own food and rely on their environment for the food source.

(1) Lactobacillus helps in the production of curd from milk.

(2) They aid in nitrogen fixation. Eg Rhizobium and Azotobacter.

(3) They're used for production of antibiotics. (streptomyces griseus is used to make streptomycin)

(b) Archaebacteria: Archaebacteria are a group of microorganisms considered to be a primitive form of life that evolved separately from the bacteria and blue-green algae.

(1) Methane gas is produced from the dung of ruminants by the methanogens.

(2) Methanogens are also involved in the formation of biogas and sewage treatment.