Introduction to scope of mirobiology << Back

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Introduction to scope of microbiology

Definition: It is the study of living organisms of microscopic size, that include essentially bacteria, fungi, algae, protozoa and the infectious agents viruses.


  • The Discovery of Microorganisms
  • The arguments over Spontaneous Generation
  • Broadly accepted fields of microbiology
  • The Scope and application of Microbiology
  • The Future of Microbiology

The Discovery of Microorganisms

Roman philosopher Lucretius (about 98–55 B.C.) and the physician Girolamo Fracastoro (1478–1553) recommended that infection was caused by invisible living creatures.  The first person to examine and explain microorganisms was the part-time microscopist Antony van Leeuwenhoek (1632–1723) of Holland. In 1673 Leeuwenhoek sent detailed findings to  Royal Society of London. He called such minute organisms as animalcules.It is clear from that he observe both bacteria and protozoa. some important events that leads to the discovery of microbiology is summarized as follows.

  1. In 1546,  Fracastoro suggests that invisible organisms cause disease
  2. During 1590–1608, Jansen develops first useful compound microscope
  3. In 1676,  Leeuwenhoek discovers “animalcules”

The arguments over Spontaneous Generation

Statement of spontaneous generation: living organisms could develop from nonliving matter. This outlook finally was confront by the Francesco Redi (1626–1697), who carried out a by a series of experiments on decaying meat and its capability to make maggots spontaneously. He placed meat in three containers. One flask was uncovered, a second flask was covered with paper, and the third flask was covered with a fine gauze that would exclude flies. Flies laid their eggs on the exposed meat and maggots developed. In other two container maggots were not produces. On gauze covered container maggots developed on the gauze. In 1748,  John boiled mutton broth and then tightly close  the flasks. In due course many of the flasks became hazy and contained microorganisms. He state that organic matter has a power to confer the properties of life on nonliving matter.

After few years  Lazzaro Spallanzani  done same experiment with some improved design. He seals glass flasks that contained water and seeds. If the sealed flasks were placed in boiling water for 45 minutes then no growth took place as long as the flask is sealed. He projected that air carried microorganisms to the nutritional medium, but also remark that the external air might be required for growth of animals already in the medium. The supporters of spontaneous generation theory supporters argued that heating the air in sealed flasks destroyed its ability to support life.

Finally Louis Pasteur  settle the the matter once and for all. Pasteur designed a swan neck flask which has variety of curves at neck region, while maintaining the ends of the necks open to the atmosphere. Pasteur then boiled the nutrient medium for a some minutes and then allowed it  to cool. No growth took place even though the contents of the flasks were uncovered to the air. He explains that no growth occurred because dust and germs had been entrapped on the walls of the curved necks. If necks is not swan shaped or they were broken, growth occurs. In this way the controversy around the spontaneous germination theory was resolved

Swan neck flask


Broadly accepted fields of microbiology

  • Bacteriology : It is the study of bacteria
  • Mycology : It is the study of fungi,
  • Phycology : It is  the study of algae
  • Protozoology : It is the study of protozoans
  • Virology : It is the study of viruses.

The Scope and application of Microbiology

Microorganisms were the primary living organisms on our earth. They were omni present. They are more plentiful than any other kind of organism, and probably it represents the largest part from the earth's biomass. The whole ecosystem depends on their activities, and their activities influences the humans in many ways. Hence  currently  microbiology is a large area with many different specialization; it has a great impact on fields such as diagnostics, medicine, agricultural and food chemistry, ecology, genetics, molecular biology and biochemistry.

One can get  the importance of microbiology in the twentieth century by analysing the award of nobel prize in physiology or medicine. More than 33 % of  these were given to scientists working on microbiology aspect.

1) Medical microbiology: It deals with the diseases of human being developed due to harmful effects of microbial pathogens.

2)Public health microbiology: Here microbiologist tries to control the spread of  communicable diseases in the society. Public health microbiologists often monitor community food establishments an water supplies to keep them safe and free from infectious diseases.

3) Agriculture microbiology:  Microbiologist tries to fight against the plant diseases that affect the important food crops, develop techniques to improve the soil fertility and crop yields. Development of biofertilizers and biopesticides are the recent examples.

4) Microbial Ecology:  It is closely related to agricultural microbiology. Microbial ecologist study the relationship between microorganism and their habitats. They are concerned with the contribution of microorganism and their habitats.   It also concern with the effect of pollution on microbes.

5) Vaterinary microbiology: This discipline deals with the pathogen of domestic livestocks and poultry. They control the spread of such diseases. They have the scope of establishing such live stock units.

6) Food Microbiology:  It deals with the food industry. Here microbiologist is responsible microbial aspects of the quality and control. They are responsible for maintain the hygienic environment in the production unit. Many products are there which are processed with the help of microorganism or they are fermentation product of microbial origin. In such units production microbiologist are required. Eg. Single cell protein, ensilage, cheese etc.

7) Dairy microbiology: This includes microbiology of cream, physical and chemical testing of milk and dairy products and microbiological and physical and chemical properties of raw milk used for processing pasteurised milk.

8) Aero microbiology: It deals with the study of atmospheric air and environment which includes pollutants as well as bacteria, bacterial spores, fungal spores and viruses etc.

9) Aquatic microbiology: It deals with the study of microorganisms in aquatic environments.

10) Water and waste water microbiology ( Sanitary microbiology) : It deals with the study related to treatment of drinking water supplies and sewage disposal.

11) Geo chemical microbiology: It deals with the applied areas such as extraction of metal from the ores. Such process is also called bioleaching.

12) Industrial microbiology: It concerned with the efficient use of microorganisms to produce economically important products and with the development of techniques used to prevent microbial destruction of economically important products formed by other ways. Pharmaceutical industries involving the microbial production of antibiotics , vitamins and aminoacids as well as microbial transformation of steroids. Production units for preparing vaccines and toxods. Production of therapeutics developed by recombinant DNA technology. Industries involved in the microbial production of organic acids and enzyme industries.

Concluding remarks:

Microbes affects the many branches of science that includes medicine, agriculture,  industry, ecology, genetics, biochemistry, molecular biology. At present and for the anticipated future, microbiologists will face several challenges to crack many of society problems including combating disease, environmental issues, and maintaining/improving the world’s food supply.


Question : 1 Which of the following is not considered a microorganism?

1: Algae
2: Bacteria
3: Protozoan
4: Mushroom

Question : 2 Which scientist is most responsible for finally laying the theory of spontaneous generation to rest?

1: Joseph Lister
2: Robert Koch
3: Franscesco Redi
4: Louis Pasteur

Question : 3 The first person to demonstrate that bacteria resides in air was

1: Robert Koch
2: Joseph Lister
3: Louis Pasteur
4: Ronald Ross

Question : 4 Who demonstrated that open tubes of broth remained free of bacteria when air was free of dust?

1: Lazzaro Sallanzani
2: Francisco Redi
3: John Tyndall
4: Louis Pasteur

Question : 5 The role of phagocytosis was discovered by

1: Paul Ehrlich
2: Elie Metchikoff
3: Louis Pasteur
4: Robert Koch

Question : 6 On which of the following Pasteur first conducted his experiments of fermentation

1: Milk
2: Fruit juices
3: Food materials
4: Both 1 and 2

Question : 7 Which of the following is correct regarding Koch’s postulate?

1: It provides guidelines to identify the causative agent of an infectious disease
2: It provides guidelines to make pure culture
3: It provides guidelines to pasteurize milk
4: It provides guidelines that to attenuate bacteria for vaccination

Question : 8 Francisco Redi did experiments on maggots which proved

1: Spontaneous generation
2: Maggots could be produced by exposing meat to air
3: Origin of the maggots was the flies
4: None of the above

Question : 9 Identify the correct match of the name of the investigator with their contribution in the field of microbiology

1: Robert Koch-developed modern concept of chemotherapy
2: Paul Ehrlich-discovered nitrogen fixing bacteria
3: Elie Metchnikoff-discovered vaccination
4: John Tyndall-developed fractional sterilization to kill spores

Question : 10 The applied aspect of microbiology is

1: Wastewater treatment
2: Industrial uses of microbes
3: Food spoilage and food production
4: All of the above

Question : 11 Public health microbiology deals with

1: The study of immune system
2: The identification and control the spread of communicable disease
3: The transmission of food borne diseases
4: The employment of microorganism to reduce pollution

Question : 12 Which of the following match is correct regarding the broadly accepted field of microbiology

1: Bacteriology: It is the study of bacteria
2: Mycology: It is the study of fungi
3: Phycology: It is the study of algae
4: All of the above
Introduction and Scope of microbiology