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Bacteria have both harmful and beneficial effect. Both harmful and beneficial effect are described below.
The harmful effects of bacteria are described below;
Spoilage of food:
Saprophytic bacteria decay or spoil our food, vegetables, jam, jelly, pickle bread. Eg; Pseudomonas
Food poisoning is caused by bacteria named as Clostridium botulinum.
Deterioration of Domestic articles;
Domestic articles like furniture, leather, cotton clothes etc are deteriorated by bacteria. Eg; Spirochaete cytophage
About 90% of diseases are caused by bacteria. Eg; Vibrio cholera
Decreases soil fertility:
Some bacteria converts phosphate and nitrate in the form of free sulphur and nitrogen due to which fertility of the soil decreases. Eg; Defulfovibrio desulfurican, Thiobacillus denitrification
Nitrifying bacteria like Nitrosomonas converts atmospheric ammonia gas in the form of nitride compound and another bacteria Nitrobacter converts nitride into nitrate form. These activities increase the fertility of the soil.
Nitrogen fixing bacteria like Clostridium and Azotobacter are free living nitrogen fixing bacteria. They fix atmospheric free nitrogen into the nitrogenous compound. Rhizobium is symbiotically occurring nitrogen fixing bacteria. They fixed atmospheric free nitrogen into the nitrogenous compound. In this way, the fertility of soil can be increased.
Saprophytic bacteria like Bacillus Vulgaris converts amino acid into ammonia gas in soil.
Dairy industries used lactobacillus in the preparation of lactic acid and Acetobacter used in the preparation of acetic acid likewise bacteria can be used in the preparation of alcohol.
Bacteria can be used in medicine. Some antibiotics are prepared by using bacteria. Eg; Streptomyces Vitamin K and Vitamin B complex can be prepared by using bacteria.
Saprophytic bacteria decompose dead bodies and organic wastage and clean nature. This activity of bacteria balance ecosystem also. They are called as nature's scavenger.