Write an essay on the economic importance of bacteria


Bacteria are unicellular and ultra-microscopic organisms, yet they play an important role in nature. They are of tremendous importance to man. They play an important role in agriculture and medicine and are the basis of many industries. Some are beneficial to man directly or indirectly, others are very harmful as they cause various plant and animal diseases. Bacteria are considered as our friends and foes due to their beneficial and harmful activities. Their economic importance can be studied under two aspects:

(A) Beneficial aspects.

(B) Harmful aspects.

(A) Beneficial Aspects:


The beneficial activities of the bacteria can be classified as follows:

(1) Role in agriculture.

(2) Role in industry and medicine.

(1) Role in Agriculture:

The activities of bacteria are very important in agriculture in the following aspects:


(a) Decaying of organic substance:

Most of the bacteria are very useful in bringing about decomposition of dead organic matter of plants and animals by the secretion of enzymes. The enzymes convert the fats, carbohydrates and nitrogenous compounds into simpler forms, such as, CO2 water, ammonia, hydrogen sulphide, phosphates, nitrates etc that are used as raw material by the green plants. Thus, these bacteria not only decompose the organic compounds but also remove the harmful waste from the earth and thus function as nature’s scavengers.

{b) Fertility of the soil:

Some bacteria maintain and others increase the fertility of the soil. They bring about physical and chemical changes in the soil by converting insoluble materials into soluble ones. These bacteria are the ammonifying, nitrifying and the nitrogen fixing Bacteria.


(i) Ammonifying Bacteria:

The decay bacteria decompose the proieinous compounds into amino acids, which are reduced to ammonia by ammonifying bacteria. The free ammonia combines in the soil to form ammonium salts. This conversion is known as ammonification. Examples are Bacillus ramosus, B. vulgaris etc.

(ii) Nitrifying Bacteria:

These bacteria convert ammonium salts into nitrates, which are absorbed by the plants. The nitrifying bacteria are the Nitrobacter and Nitrosomonas. The Nitrosomonas oxidize the ammonium salts into nitrous acid, which forms nitrites in the soil. The Nitrobacter then converts the nitrites into nitrates. This conversion of ammonium salts into available nitrates is called nitrification.


(iii) Nitrogen Fixing Bacteria:

These bacteria take up nitrogen from the atmosphere and convert it into organic nitrogen compounds. It is known as nitrogen fixation. The nitrogen-fixing bacteria are of two types. One type includes Azotobacter and Clostridium, which live freely in the soil and fix nitrogen of the air in their bodies in the form of nitrogenous organic compounds. The other types of bacteria are the nodule bacteria, the Bacillus radicicola. Rhizobium lives as symbiont in the roots of leguminous plants and forms nodules. These bacteria absorb free nitrogen from the bacterial cell. The leguminous plants thus enrich the fertility of the soil. They are grown for green manuring and rotation of crops.

(2) Role in Industry and Medicine:

Bacteria play a very important role in various industries. The products obtained as a result of bacterial activities cannot be chemically prepared. Their activities are involved in the following industries:

(a) Preparation of Alcohols:


Ethyl alcohol and butyl alcohol are manufactured by the bacterial acivities in the sugar solution, e.g., Clostridium acetobutylicum.

(b) Preparation of Vinegar:

Vinegar is prepared by the activities of Acetobacter aceti in the sugarcane juice.

(c) Preparation of Butter, Cheese etc.:

The preparation of butter, cheese etc. is done by bacteria. The Lactobacillus lactis is responsible for souring of milk resulting in curd (dahi) preparation. Bacterial activities also impart the typical flavours.

(d) Preparation of Tea, Coffee etc.:

Bacteria are very useful in preparation and flavouring of tea, coffee, cocoa etc. e.g., Micrococcus.

(e) Preparation of Tobacco:

Tobacco leaves are cured and flavoured by the bacteria. Typical types of bacteria are cultured for this purpose, e.g., Micrococcus.

(f) Preparation of Hemp fibres:

Fibres from the hemp are isolated after rotting the stems by activity of bacteria (e.g., Clostridium butyricum). The bacteria eat up the protoplasmic tissues but leave the sclerenchyma fibres.

(g) Preparation of Leather and Tanning:

The hairs and fats are removed from the skin by the action of bacteria in the leather industry.

(h) Preparation of Antibiotics:

The bacteria are also used in the preparation of antibiotics. According to Sir Alexander Fleming, the growth of harmful Staphylococcits is checked by Penicillium natatum. With this discovery, large number of antibiotics has been prepared which are of great importance in the medical world. Tyrothricin, Subtillin, Polyximin-B, Bacitracin, Streptomycin, Aureomycin, Terramycin are some well-known antibiotics.

(B) Harmful Aspects:

Bacteria are also harmful to man directly or indirectly. They cause various diseases in plants, human beings or domestic animals. The harmful bacteria are of the following types ;

(i) Animal pathogenic Bacteria.

(ii) Plant pathogenic Bacteria.

(iii) Food destroying Bacteria.

(iv) Soil fertility destroying Bacteria.

(i) Animal Pathogenic Bacteria:

There are a large number of parasitic bacteria, which cause various serious diseases in man and domestic animals, sometimes in epidemic form. They arc invisible enemies. Some of the common human diseases producing bacteria are Mycobacterium tuberculosis causing tuberculosis, Eberthela typhosa causing typhoid, Clostridium tetani causing tetanus, Shigella dysenteriae causing dysentery, Hemophilous influenzea causing influenza, Corynebacteriaum diphtlteriea causing diphtheria, Diplococats pneumonias causing pneumonia, Vibrio cholerae causing cholera, Streptococcus causing blood poisoning, Treponema pallidium causing syphilis, Gonococcus causing gonorrhoea, Bacillus pestis causing plague etc. In domestic animals various diseases are caused by bacteria, e.g., Anthrax, Pneumonia, Tuberculosis, Cholera, Glanders etc.

(ii) Plant Pathogenic Bacteria:

Many parasitic bacteria cause serious diseases in cultivated plants, which cause great harm to the crops. Important diseases are Citrus canker, fire blight of pear, cotton root rot, walnut blight, potato rot, pineapple rot etc. The Canker of Citrus (orange and lemon) is caused by Xanthonionas citri. The rot diseases cause black spots on potato, tomato, cabbage, carrot etc.

(iii) Food destroying Bacteria:

Some saprophytic bacteria are responsible for the decay of human foodstuffs including meat, milk, vegetables, fruits etc. These bacteria spoil foodstufs and make them unpalatable and poisonous, e.g., souring of milk, rotting of meat, vegetables, fruits etc. Staphylococcus and Clostridium botulinum cause food poisoning when rotten food is eaten,

(iv) Soil Fertility destroying Bacteria:

These are denitrifying bacteria in the soil, which reduce the nitrates, and the ammonium salts to free nitrogen, which escapes into the atmosphere. This process is known as denitrification, which decreases the fertility of the soil, e.g., Bacillus denitrificans.

These bacteria are often abunbant in the poorly drained and heavily manured soil. So the denitrifying bacteria are the natural enemies of the farmers.

Thus with the study of economic importance of bacteria we conclude that bacteria are our friends due to their beneficial aspects and enemies due to their harmful aspects. But in the bacteria beneficial aspects overweigh their harmful aspects. We can control the harmful activities but their beneficial activities cannot be replaced by artificial processes. So the bacteria are our friends more and enemies less.


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