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Economic Importance of Bacteria

Bacteria are our 'friends and foes' as they have both useful and harmful activities.


Role of bacteria in agriculture

Some free-living nitrogen fixing aerobic bacteria like Azotobacter and Clostridium have the capacity of fixing atmospheric nitrogen into nitrogenous substances, hence increase soil fertility. Similarly symbiotic bacteria Rhizobium also fixes atmospheric nitrogen. All nitrogen fixing bacteria have ‘nif’ genes (nitrogenase inducing factor). e.g., Nitrosomonas, Nitrosococcus, Nitrobacter, Nitrospina. Nitrospira and Nitrococcus. Nitrosomonas converts ammonia into nitrites, which is further converted into nitrates by Nitrobacter (nitrification).

Role of bacteria in dairy industry

Lactic acid is commercially produced by using Lactic acid bacteria. The bacteria convert lactose of milk into lactic acid and hence milk turns sour. Lactic acid bacteria unite casein protein of milk in the form of small droplets and thus form curd and hence butter.

Role of bacteria in other industries

Many antibiotics are produced from bacteria. The first antibiotic produced was penicillin (wonder drug) obtained from fungus Penicillium notatum by Sir Alexander Fleming (1923), which checks growth of gram-positive bacteria by inhibiting cell wall synthesis or by blocking peptidoglycan synthesis.

Interferons are protein molecules or polypeptides of low molecular weight which prevent viral multiplication.

Some clinically important antibiotics


Producer organism


Site or mode of action


Penicillium chrysogenum

Gram-positive bacteria

Wall synthesis


Cephalosporium acremonium

Broad spectrum

Wall synthesis


Penicillium griseofulvum

Dermatophytic fungi



Bacillus subtilis

Gram-positive bacteria

Wall synthesis

Polymyxin B

Bacillus polymyxa

Gram-negative bacteria

Cell membrane

Amphotericin B

Streptomyces nodosus


Cell membrane


Streptomyces erythreus

Gram-positive bacteria

Protein synthesis


Streptomyces fradiae

Broad spectrum

Protein synthesis


Streptomyces griseus

Gram-negative bacteria

Protein synthesis


Streptomyces rimosus

Broad spectrum

Protein synthesis


Streptomyces orientalis

Gram-positive bacteria

Protein synthesis


Micromonospora purpurea

Broad spectrum

Protein synthesis


Streptomyces mediterranei


Protein synthesis


Role of bacteria in petroleum pollution

Petroleum pollution in water bodies is checked upto some extent by Pseudomonas.

Genetically engineered strain of Pseudomonas putida (Superbug) was developed by Dr. Ananda Mohan Chakraborty which biodegrade spilled oil. These superbugs were allowed by USA government in 1990 for removal of oil from water.



  • Food-poisoning (Botulism): It is caused by Clostridium botulinum. The main symptoms are vomiting followed by paralysis and death.

  • Reduction of soil fertility: There are some denitrifying bacteria in soil, which convert nitrates into free nitrogen (denitrification), e.g, Bacillus denitrificans, Micrococcus denitrificans and Thiobacillus denitrificans.

  • Many pathogenic bacteria such as Vibrio cholera, Salmonella typhi, Shigella dyseinteriae cause Cholera, typhoid and dysentery respectively.

  • The crown gall diseases in plants is caused by Agrobacterium tumefaciens (Rhizobium radiobacter, synonym Agrobacterium radiobacter) and  the hairy root root diseases is caused by Agrobacterium rhizogenes

  • The common sulphur oxidizing bacteria are Thiobacillus thiooxidans and Beggiatoa. Cotton spoilage is due to Spirochaete cytophage.

  • Most of the pathogenic bacteria are gram negative, rod-shaped (Bacillus) and non-spore forming. However, bacteria causing anthrax and tetanus are endospore forming or spore forming.

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