Economic importance of prokaryotes and its roles

Economic importance of prokaryotes (microorganisms) and its roles

Role of bacteria and cyanobacteria in nitrogen cycle

(Role as Biofertilizers)

Bacteria and cyanobacteria play important role in nitrogen cycle.

(a)    Biological nitrogen fixation

The synthesis of organic nitrogenous compounds from atmospheric nitrogen by certain microorganisms is called biological nitrogen fixation. Bacteria and cyanobacteria play following role in biological nitrogen fixation:

I. Aerobic bacteria and anaerobic bacteria: They are saprophytic

organisms. Therefore, these fix nitrogen only in the soil. This soil must have good supply of organic manure. The example of anaerobic bacteria is Clostridium and the _example of aerobic bacteria is Azotobacter.

  1. Nodule forming Rhizobium species play role in symbiotic nitrogen fixation. These bacteria live in nodules. A large number of leguminous plants like bean, pea, gram and soybean develop root nodules. All the plants of family Papilionacae develop nodules.
  2. Role of Cyanobacteria: Blue green algae are autotrophic photosynthetic organisms. They grow in waterlogged and wet soil like paddy (rice) fields. Members of families Nostocales and Stigonematales are important nitrogen fixture. Some of its examples are:(a)Anabaena is an important member. It consists of branched filaments. These filaments are made up of two types of cells Green photosynthetic cells fix the atmospheric carbon dioxide and release oxygen during photosynthesis. Ileterocysts are slightly enlarged colourless cells. These are non-photosynthetic. They can fix atmospheric nitrogen aerobically.(h) Blue green algae living in higher plants: The blue-green algae are free living in the soil. Some blue green algae enter into the tissues of higher plants. They permanently live inside. For example Nostoc lives in the mucilage cavities of Anthoccros and fixes atmospheric nitrogen.(c) Lichens: Nostoc and Scytonema develops symbiotic association with fungi. This association is called lichens. The algal components fix the molecular nitrogen in the form of organic compounds.Caere OTS IliCansw-HOI COMpenen Inc Pennnaitn incur cid be reprodncmon di•P*


(b)        Release of nitrogen by decomposition Nitrogen also present in dead plants and animals. Bacteria decompose these dead plants and animals and form nitrates and


Monera (Prokaryotes)

ammonia. These compounds are used up by plants. It has following steps:

  1. Ammonifying bacteria: The bacteria ,which causes ammonization are called ammonifying bacteria. Soil contains many organic materials in the form of complex organic compounds like protein, amino acids, nucleic acid and nucleotides. Most of the nitrates are formed in the soil by the decomposition of these organic compounds. Example of ammonifying bacteria is Nilrobaclor.
  2. Nitrifying bacteria: Several bacteria in soil oxidize ammonia or ammonium ions in to nitrates. These bacteria are called nitrifying bacteria. This oxidation is known as nitrification. Nitrates are absorbed by plants. Example of nitrifying bacteria is Azobactor
  3. Denitrifying bacteria: Some bacteria like pseudomonas change nitrates into nitrogen gas. These are called denitrifying bacteria.


Pathogenicity is the ability of a pathogen to produce an infectious disease in an organism. It is often used interchangeably with the term “virulence”, But some authors reserve the term virulence for descriptions of the relative degree of damage done by a pathogen. Virulence is the ability of an organism to invade the bloodstream.

Pathogenic bacteria are bacteria that cause infectious diseases. Vast majority of bacteria are harmless or beneficial. But quite a few bacteria are pathogenic. One of the bacterial diseases with highest disease burden is tuberculosis,caused   by the bacterium Mycobacterium tuberculosis. It kills about 2 million people a year. Pathogenic bacteria contribute to other globally important diseases, such as pneumonia. It is caused by bacteria such as Streptococcus and Pseztdomonas. They also cause foodbome illnesses,which is caused by bacteria  such as Shigella,Campylobacie• and Salmonella. Pathogenic bacteria also cause infections such as tetanus, typhoid fever, diphtheria, syphilis and leprosy. Koch’s postulates are used to establish relationship between a causative microbe and a disease. Each pathogenic species has a characteristic spectrum of interactions with its human hosts. There are four groups of pathogenic bacteria.

I. Conditionally pathogenic: Conditionally pathogenic bacteria are only pathogenic under certain conditions like wound that allows for entry into the blood.

For example, Staphylococcus or Streptococcus are also part of the normal human flora. It lives on the skin or in the nose without causing disease. But it can potentially cause skin infections, pneumonia, meningitis and even sepsis. Sepsis is systemic inflammatory response producing shock, massive vasodilation and death.

  1. Opportunistic Pathogens: Some species of bacteria, such

as Pseudomonas      aeruginosa, Burkholderia       cenocepacia,
and Mycobacterium avium,
are opportunistic pathogens. They

cause disease mainly in people suffering from immunosuppression or cystic fibrosis.

  1. Obligate intracellular pathogens: Some other bacteria are obligate intracellular parasites. They are able to grow and reproduce only within the cells of other organisms. Still, !nfections with intracellular bacteria may be asymptomatic, such as during the incubation period. An example of intracellular bacteria is Rickettsia. One species of Rickettsia causes typhus. Another cause Rocky Mountain spotted fever.

Chlamydia, another phylum of obligate intracellular parasites, contains species that can cause pneumonia, or urinary tract infection. They may also be involved in coronary heart disease.



  1. Facultative                  intracellular                 pathogens:
    Mycobacterium and Bruce/la live intracellularly. But they are facultative parasites. They can also damage some internal organs.

Prevention from bacteria

There are different methods to prevent bacteria from attacking: 1. Physical Methods

The use of physical methods to control bacteria is known as sterilization. Steam, dry heat, gas, filtration and radiations are used in process of sterilization. Sterilization destroys all the microorganisms. Following methods are used for sterilizations:

• High temperature is used in microbiological labs for the

controlling of microbes. Both dry and moist heat is effective. Moist heat causes coagulation of proteins. It kills the microbes. Dry heat causes the oxidation of chemical compounds of the

microbes and kills them.

  • Certain electrochemical radiations below 300 nm are effective for the killing bacteria. Gamma rays are used for the sterilization process.
  • Membranous filters can sterilize the heat sensitive compounds iike antibiotics, serum and hormone etc.

Chemical Methods

Antiseptics, disinfectants and chemotherapeutic agents can be used for microbial control.

  1. Antiseptics: Chemical substances used on living tissues (outside the body) that inhibit the growth of microorganisms are called antiseptics. Antiseptics are mostly used on wounds.
  2. Disinfactant: The chemical agents used on non-living material

(surgical instrument etc) that inhabit the growth of vegetative cells of microorganisms are called disinfectant. The important chemical agents used for disinfection are oxidizing and reducing agents. For example halogens (chlorine), phenols, hydrogen peroxide, potassium per magnate, alcohol and formaldehyde etc.

Treatment of bacterial diseases

Bacterial infections are treated with antibiotics. There are two classes of antibiotics:

a)     Bacteriocidal: The antibiotics which kill bacteria are called bacteriocidal

b)     Bacteriostatic: If they just prevent bacterial growth, then these are called bacteriostatic.

There are many types of antibiotics. Each class inhibits a process that is different in the pathogen from the host. For example, the antibiotics     chloramphenicol    and tetracyclin inhibit   the
bacterial ribosome. But they do not affect the structurally-different eukaryotic ribosome. Therefore, they exhibit selective toxicity. Antibiotics are used both in treating human disease and in intensive farming. Both these uses have caused antibiotic resistance in bacterial populations.

Industrial role of bacteria and cyanobacteria

Prokaryotes play important role in industry. Some of these are:

1. Role in food industry: Bacteria play important role in fermentation. So they are used for manufacturing butter, yogurt, cheese, cakes and bear.

  1. Role in pharmaceutical industry: Many antibiotics are obtained from bacteria. Some of these antibiotics are streptomycin, Terramycin etc. Recombinant bacteria are used to synthesize insulin, growth factors and other pharmaceutical products.
  2. Role in energy production: The entire world is facing the problem of shortage of energy. Bacteria are used to produce biogas. Biogas is used as alternative resource of energy.
  3. Role in agriculture: Bacteria are used as pesticides for biological control. It is most effective and cheap method of controlling pests.
  4. Role in Dairy farms: Bacteria are used to prepare silage for dairy animals. Silage is used as fodder.
  5. Role in mining industry: Many bacteria are used for the extraction of metals from mine. Now recombinant bacteria have been prepared. They selectivity extract metals from raw ore.
  6. Role in textile industry: Some bacteria like clostridium are used for retting of hemps, jute and flax. These bacteria separate the fibers. These fibers are used for making clothes and ropes.
  7. Leather industry: Bacteria are used for preparing commercial leather.
  8. Role in tobacco industry: Bacteria are used for drying tobacco leaves. These leaves are used for preparing cigarettes.
  9. Role in disposal of wastes: Bacteria are natural decomposer. They degrade the industrial and domestic wastes. Some transgenic bacteria are used as biofilter.
  10. Role in bioremediation: The ability of bacteria to degrade a variety of organic compounds is remarkable. This ability is used in waste processing and bioremediation. Bacteria capable of digesting the hydrocarbons in petroleum. Therefore, they are often used to clean up oil spills. Bacteria are also used for the bioremediation of industrial toxic wastes.
  11. Role in biological control: “Bacteria can also be used in the place of pesticides in the biological pest control. The commonly

used     bacteria       for     biological         control        are Bacillus ilturingiensis (also called BT). It is a Gram-positive, soil dwelling bacterium. Subspecies of this bacterium are used as a Lepidopteran-specific insecticides. Because of their specificity, these pesticides are regarded as environmentally friendly. It has little or no effect on humans, wildlife, pollinators and most other beneficial insects.

13. Uses in research: Bacteria are extensively used in molecular biology, genetics and biochemistry. The biologists make mutations in bacterial DNA. Then they examine the resulting phenotypes. Then the scientists can determine the function of genes, enzymes and metabolic pathways in bacteria. They then apply this knowledge to more complex organisms


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