17 Applications of Microbiology

Some of the major applications of microbiology are as follows:

Microbiology is one of the most applied branches of science. Its outstanding applications in the field of food microbiology, medical microbiology, industrial microbiology, soil microbiology, water and wastewater microbiology, microbial technology (biotechnology), extraction of metals and environmental microbiology including the use of microorganisms as biosensors is as given below.

1. It provides us with information about different types of microorganisms enabling us to understand their structure and functions; identifications and differentiations; their classifications; nomenclatures (naming), requirements regarding their nutrition; their isolation and purification; as plant and human pathogens; to derive phylogenetic relationships (relationships according to developmental stages in the evolution of an organism) and to understand the origin of life itself.

2. Microorganisms as food: Besides comestible fungi like mushrooms, microorganisms are also being used as single cell protein in the form of yeasts, bacteria, cyanobacteria, fungi as human food or animal feed. The production of the algal microbes as Chlorella (green alga and Spirulina (cyanobacterium) are being produced in Japan, Taiwan, Mexico, Israel, Thailand and America. Production of cellulose or lignocellulose utilizing microorganisms serves as human food as such or in the form of their products. Microbial products are also used as animal feed.

3. Microorganisms are used in production of a large number of, fermented foods such as leavened bread, sourdough bread, fermented milk products and flavours. The fermented milk products are yoghurt, cheese and several other products.

4. The important fermented vegetables are sauerkraut (from cabbage) and Kimchi (from other fermented vegetables in Korea).

5. Fermented meats and fermented fish are used in different parts of the world due to their increased retentivity, otherwise the meats and fish are highly perishable.

6. Beer, vinegar, tempeh, soya sauce, rice wine too are fermented products.

7. Microbiology has been very useful in preservation of food by heat processing, by pasteurization and appertization (commercially sterile food), by calculating thermal death values, prevention of spoilage of canned foods, aspectic packaging, irradiation, UV radiation, ionizing radiation, high pressure processing, i.e., pascalization, low temperature storage (chill storage and freezing), chemical preservatives (organic acids, esters, nitrite, and sulphur dioxide).

In food microbiology one learns about bacterial and nonbacterial agents of food borne illness. Among the helminthes and nematodes are: Platyhelminthus (i.e. liver flukes and tapeworms) and roundworms (e.g., Trichinella spiralis). The protozoa that cause food borne diseases are Giardia lamblia and Entamoeba histolytica.

8. Microbial diseases: Microorganisms are the causative agents of a large number of diseases which have been described under a separate chapter.

9. Industrial Microbiology: A large number of products of microbial metabolism after microbial processing of raw materials are produced on industrial scale. A separate chapter has been given on ‘Industrial Microbiology’.

10. Energy from microbial sources: A number of substrates can be used as a source of energy as biogas from methanogenic microorganisms. The microbes like Methanobacterium and Methanococcus can utilize CO₂ as an electron acceptor finally producing methane. A new species of Methanobacterium, i.e., M. cadomensis strain 23 has been evolved in Japan for faster production of methane. Ethanol can also be used for the production of gasohol by mixing 80 per cent gasoline and 20 per cent ethanol.

11 .Degradation of cellulose and lignin:

Trichoderina reesei can be used to degrade cellulose since it produces extracellular cellulase. The white rot fungus Sporotrichum pulverulentum is a cellulase negative organism but a mutant of it has been prepared which can degrade kraft and wood lignocellulase actively. It has been possible to produce biological pulp without any chemical treatment for delignification.

12. Mining and extraction of metals:

Thiobacillus ferrooxidans and combination of Leptospirillum ferroxidans and Thiobacillus organoparpus can be used to degrade pyrite (FeS₂) and chalcopyrite (CuFeS₂). The archaeal species Sulfolobus acidocaldarius and S. brierlevi are capable of oxidizing sulphur and iron for energy depending on C0₂ or other simple organic compounds for carbon. The pyrite and chalcopyrite are also degraded by these archaeobacterial species.

13. Recombinant DNA and genetic recombination:

Recombinant DNA is a wonderful product of genetic engineering, i.e., manufacturing and manipulating genetic material in vitro. The process of joining DNA from different sources is genetic recombination. A large number of restriction enzymes/restriction endonucleases have been obtained from various microorganisms that can cut or cleave double stranded DNA leaving staggered ends.

14. Hybridoma and preparation of monoclonal antibodies:

Hybridoma is a cell made by fusing an antibody-producing B-cell with a cancer cell. The resulting hybrid myeloma or hybridoma cells have properties of both parent cells immortality and the ability to secrete large amounts of a single specific type of antibody. This was discovered by Kohler.

15. Harvesting DNA biotechnology for public health engineering programmes:

Such programmes include production of interferon which is an antiviral protein produced by certain animal cells in response to a viral infection, production of human insulin production of somatotropin a human growth hormone and production of a large number of other hormones and vaccines.

The vaccines for cholera, diphtheria, tetanus, pertussis, viral hepatitis type A, type B, influenza, mumps, measles (rubella) plague, poliomyelitis, rabies, rubbela, typhoid, typhus and yellow fever have been developed so far.

16. Microbial technology of nitrogen fixation exploiting symbiotic microorganisms in association with lower or higher plants and asymbiotic or nonsymbiotic (by nitrogen fixing microorganisms independently).

Detailed information is covered under a separate chapter on ‘biofertilizers’. In nature, in legume root nodules a red pigment containing protein called leghaemoglobin is involved in the process of nitrogen fixation. The key enzyme responsible for biological conversion of molecular nitrogen to ammonia is nitrogenase.

17. Making faster and smarter computers:

The Archaeobacterium Halobacterium halobium grows in nature in solar evaporation ponds having high concentration of salts. Such salty ponds are found around San Francisco Bay located on the Western coast of USA.

It has been found that the plasma membrane of Halobacterium halobium fragments into two fractions, when the cell is broken down. These two fractions are red and purple. The purple fraction is important in making computer parts (chips). The purple colour is due to a protein which is 75% of purple membrane and has been referred to as bacteriorhodopsin.

Robert Birge at Syracuse University’s Centre of Molecular Electronics has grown Halobacerium halobium in 5-litre batches and has extracted the protein bacteriorhodopsin from the cells and developed the computer chips which are made up of a thin layer of bacteriorhodopsin.

The chips so made from the bacterial source can store more information than the conventional silicon chips and process the information faster more like a human brain. The only drawback is that one needs to store the protein chips at -4°C. But Birge believes that this problem will be overcome soon.