(i) Prevention of environmental pollution: Bacteria break down the organic wastes of the environment into simple substances. By oxidizing the complex material, making it suitable for reuse. This is why bacteria are called natural scavengers. Bacteria such as Pseudomonas, Nocardia, Mycobacterium etc. convert petroleum waste into simple compounds in the presence of oxygen.
(ii) Healthy sewage system: Bacteria keep the sewage system healthy by rapidly converting organic waste into liquid. Zooglea ramigera bacteria play an important role in organic waste conversion.
(iii) Oil removal: Oil consuming bacteria are used to remove floating oil in sea water. Pseudomonas aeruginosa is an oil-eating bacteria.
(iv) Biological control: Bacteria are used to suppress the larvae of harmful pests.

(i) Digestion: E. coli and Bacillus help in human digestion.
(ii) Cellulose Digestion: Cattle have a type of bacteria in their intestines. It produces the cellulose digesting enzyme cellulase. Cellulase helps in digestion of hay, grass, leaves, cell walls etc.
(iii) Vitamin production: E. coli and other bacteria in the human intestine produce and supply vitamins B1, B2, K, biotin etc.
(iv) Insulin production: E. coli bacteria are used to produce insulin hormone. It controls diabetes.
(v) Genetic engineering: Agrobacterium tumefaciens and E. coli bacteria are of immense importance in genetic engineering.
(vi) Preparation of dairy food: curd, cheese, butter etc. are made from milk. Bacteria like Streptococcus lactis, Lactobacillus etc. are used to make these foods.
(vii) Probiotic bacteria: About 500 species of bacteria live in the human digestive system as mitotic bacteria. All these bacteria are called probiotic bacteria. Probiotic bacteria help in human digestion. So they are considered as friendly and helpful bacteria of humans.

(i) Production of Vitamins: E. coli bacteria living in human digestive system synthesize Vitamin-B, Vitamin-K2, Thiamin, Riboflavin, Folic Acid, Biotin etc. Currently, several species of bacteria are used to produce vitamins in the fermentation process.
(ii) In dairy industry: Lactobacillus and Streptococcus bacteria are used to make curds, cheese, butter, ghee, whey etc. from milk.
(iii) In leather industry: Hair is removed from leather by tannin process. The rawhide is then twisted and softened using bacterial protease enzymes.
(iv) Processing: Processing of tea, coffee, tobacco etc. requires enzymes secreted by bacteria. This results in the origin of taste and smell. Bacillus megaterium bacteria is used in this case.
(v) Production of organic gas: At present organic gas such as methane, butane is being produced by decomposing dung and garbage with the help of bacteria. Bacteria like Bacillus, E. coli, Clostridium, Methanococcus etc. produce biogas.
(vi) Salt making: Bacteria are used to make tasting salt.
(vii) In chemical industry: Bacteria are used to make chemicals like vinegar (Acetobacter xylinum), lactic acid (Bacillus lacticacidi), acetone (Clostridium acetobutylicum), alcohol, enzymes, vitamins etc.
(viii) Enzyme production: Enzymes are produced from bacteria such as Bacillus subtilis, Clostridium histolyticum, Trichoderma konigi etc.
(ix) Alcohol and acid production: Various acids and alcohols are produced from starch using Clostridium and Bacillus bacteria.

Ruminococcus albus and Ruminococcus flavefaciens bacteria live in the stomach of cattle. All these bacteria produce cellulase enzyme. Cellulase enzymes aid in the digestion of raw grasses and plants.

Jute is decomposed with the help of bacteria like Clostridium butricum and fibers are separated.

Paddy straw, grass and leguminous plants are cut into small pieces. The pieces are mixed with chitagur and kept in a sealed container. During the fermentation process Lactobacillus bacteria turn them into high quality cow feed. This cow feed is called silage.

At present organic fertilizers are being produced by decomposing dung and garbage with the help of bacteria. Organic fertilizers are being used instead of chemical fertilizers on the land.

By applying some bacteria to the field, it was possible to increase the yield of rice by 31.8% and the yield of wheat by 20.8%.

Some bacteria are used as insecticides in the field. For example, Bacillus thuringiensis.

In the process of nitrification, nitrite is produced from ammonia under the action of nitrifying bacteria. Nitrite is then produced from nitrite. Nitrate increases soil fertility.