Economic Importance of Bacteria

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

 (A) USEFUL 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
Antibiotic	Producer organism	Activity	Site or mode of action
Penicillin	Penicillium chrysogenum	Gram-positive bacteria	Wall synthesis
Cephalosporin	Cephalosporium acremonium	Broad spectrum	Wall synthesis
Griseofulvin	Penicillium griseofulvum	Dermatophytic fungi	Microtubules
Bacitracin	Bacillus subtilis	Gram-positive bacteria	Wall synthesis
Polymyxin B	Bacillus polymyxa	Gram-negative bacteria	Cell membrane
Amphotericin B	Streptomyces nodosus	Fungi	Cell membrane
Erythromycin	Streptomyces erythreus	Gram-positive bacteria	Protein synthesis
Neomycin	Streptomyces fradiae	Broad spectrum	Protein synthesis
Streptomycin	Streptomyces griseus	Gram-negative bacteria	Protein synthesis
Tetracycline	Streptomyces rimosus	Broad spectrum	Protein synthesis
Vancomycin	Streptomyces orientalis	Gram-positive bacteria	Protein synthesis
Gentamicin	Micromonospora purpurea	Broad spectrum	Protein synthesis
Rifamycin	Streptomyces mediterranei	Tuberculosis	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.

(B) HARMFUL ACTIVITIES

• 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.