The economic importance of a bacteria which is prokaryote and microscopic organism is: 1. Beneficial effects of Bacteria: A) Role in agriculture a) Bacteria as Scavenging: Saprophytic bacteria obtain food from organic remains such as animal excreta, fallen leaves, meat etc. They decompose these substances by the action of digestive enzymes aerobically or anaerobically (known as fermentation). Thus they help in sanitation of nature, so also known as scavengers. E.g. Pseudomonas) Nitrification: Rhizobium bacteria, living in root nodules of leguminous plant symbiotically, helps in fixing atmospheric nitrogen. Similarly, Nitrosomonas and Nitrococcus convert ammonium salt to nitrites. Nitrites are further changed to nitrates by Nitrobacter and Nitrocystis. It enables plants to uptake nitrogen. c) Production of Organic Manure: As stated above, saprophytic bacteria help in breaking of the complex organic substance to simpler forms. Thus, in this process, they help to convert farm refuse, dung and other wastes to manure. d) Preparation of Ensilage: Ensilage is preserved cattle fodder prepared by packing freshly chopped fodder sprinkled with molasses. Fermentation activity of bacteria produces lactic acid that acts as a preservative in ensilage.e) Production of fuel: Bacteria, while converting animal dung and other organic wastes to manure, help in the production of fuel that is a must in gobar gas plant.f) Disposal of sewage: Bacteria help in disposal of sewage by decomposing it and thus, help in environmental sanitation.B) Bacteria role in Industry a) Dairy Industry: Bacteria such as Streptococcus lactis convert milk sugar lactose into lactic acid that coagulates casein (milk protein). Then, milk is converted into curd, yogurt, cheese etc needed for the industry.b) Production of Organic Compounds: Fermentation (breakdown of carbohydrate in absence of oxygen) action of various bacteria produces organic compounds like lactic acid (by Lactobacillus), acetic acid (by Acetobacter aceti), acetone (by Clostridium acetabutylicum) etc.c) Fibre Retting: The action of some bacteria like Clostridium,Pseudomonas etc. help in fiber retting i.e. separation of stem and leaf fiber of plants from other softer tissue.d) Curing: The leaves of tea and tobacco, beans of coffee and cocoa are cured off their bitterness with the help of action of certain bacteria such as Bacillus megatherium.e) Production of Antibiotics: Number of antibacterial and antifungal antibiotics such as Hamycin, Polymyxin, Trichomycin etc are obtained from mycelia bacteria (like Streptomyces). Similarly, Bacillus is used for the production of antibiotics such as Bacitracin, Gramicidin etcf) Production of Vitamins: Different kinds of vitamins are produced from bacteria like Riboflavin from Clostridium butylicum, Vitamin B12 from Bacillus megatherium and Vitamin K and B-complex from Escherichia coli.2. Harmful effects of Bacteria: Though bacteria play important role in agriculture, industries and natural sanitation etc, it has the following harmful effects: a) Food Spoiling: Saprophytic bacteria always not only help in decomposition of dead matters, but they also cause the rotting of vegetables, fruits, meat, bread etc.b) Food Poisoning: Bacteria like Staphylococcus aureus cause food poisoning and cause people diarrhea and vomiting.c) Damaging domestic articles: Spirochete cytophaga deteriorates cotton, leather, and wooden articles.d) Denitrification: Bacteria such as Thiobacillus and Microbacillusconvert nitrate of the soil to the gaseous nitrogen. This hampers plants very much.e) Desulphurization: Bacteria such as Desulfovibrio convert soil sulfates into hydrogen sulfide.f) Cause of Diseases: It is known that over 90% of human diseases and over 10% of plant diseases are caused by bacteria.