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  Historical Aspects of Microbiology, Biology tutorial

Introduction:

The history of microbiology is the story of men and women who developed a method, a tool or a theory which was usually adopted in studying of the microorganisms. It is as well the history of events and metamorphosis of microbiology as a science.

Discovery of Microorganisms:

The beginning of the microscope allowed the studying of microorganisms. The first microscopes were simple ground glass lenses which magnified images of formerly unseen microorganisms. Among the first to observe this formerly unseen and invisible microbial world were Robert Hooke and Anthony Van Leeuwenhoek.    

1) Robert Hooke (1635-1703), an English mathematician and natural historian.

a) He coined the word 'cells' to explain the 'little boxes' he noticed in examining cork slices by a compound microscope.

b) He was the first to propose a known explanation of the microorganisms.

c) He made microscopic examination and the earliest explanation of most of the fungi.

d) Different species of fungi were clearly recognized in his drawing and recorded in his book Micrographia.

2) Anthony Van Leeuwenhoek (1632-1723) lived in Delft, Holland.

He was a draper and an amateur microscope builder. He learned lens grinding as a hobby and made above 100 simple microscopes each capable of magnifying an image around 300 times.

By employing simple microscopes, he observed microscopic organisms which he termed as 'animalcules'.

He made sketches of the various shapes of bacteria. He was the first person to publish extensive and accurate examinations of microorganisms. He is acknowledged as the father of bacteriology.

The Spontaneous Generation Conflict:

The theory of spontaneous generation defines that living organisms could build up from non-living matter. The proponents of the concept of spontaneous generation claim that living organisms could build up from non-living or decomposing matter.

1) Francesco Redi (1626-1697) challenged this concept by exhibiting that maggots on decaying meat came from the fly eggs put down on the meat, and not from the meat itself.

a) He carried out a sequence of experiments on decaying meat and its capability to generate maggot spontaneously.

b) He put meat in three distinct containers, one was not covered, and the second was covered by fine gauze to keep out flies.

c) Flies laid eggs on the exposed meat and maggots developed.

d) The two other meats didn't produce maggots. Spontaneously, flies were fascinated to the gauze-covered container and laid their eggs on the gauze, these afterward generated maggots. Therefore, it become obvious that the generation of maggots resulted from the presence of fly eggs and that meat (that is, a non-living matter) didn't spontaneously produce maggots as earlier assumed.

2) Louis Jablot (1670) conducted an experiment in which he splitted a hay infusion that had been boiled into two containers: a heated container which was closed to the air and a heated container that was freely open to the air. Just the open vessel developed microorganisms. This further assist to disprove the abiogenesis.

3) John Needham (1713-1781) represents that mutton broth boiled in flasks and then sealed could still build up microorganisms that supported the theory of spontaneous generation.

4) Lazzaro Spallanzani (1729-1799) represents that flasks sealed and then boiled had no growth of microorganisms, and he recommends that air carried germs to the culture medium. He as well stated that external air might be required to support the growth of animals already in the medium. The latter theory was appealing to the supporters of spontaneous generation.

5) Louis Pasteur (1822-1895) was a Professor of Chemistry. He developed a sequence of swan necked flasks termed as Pasteur-flasks, filled the flasks by broth and heated the broth to sterilization. After cooling, the flasks were opened to the air; however bends on the neck of the flasks prevented microorganisms from falling on the broth and contaminating it instead the microorganisms fell on the neck of the bottle. Pasteur verified that no growth occurred as dust and germs were trapped on the wall of the curved necks. If the neck were broken, growth will take place. By these experiments he challenged and defeated the theory of spontaneous generation.

Recognition of the role of Microorganisms in Disease:

1) Agostino Bassi (1773-1856) exhibit that a silkworm disease was caused due to fungus.

2) M. J. Berkerley (ca. 1845) explained that the great potato blight of Ireland was caused due to fungus.

3) Joseph Lister (1872-1912) build up a system of surgery designed to prevent the microorganisms from entering wounds. He implemented the utilization of sterile surgical instrument and employed carbolic acid (phenol) throughout surgery and on wound dressings. 

4) Robert Koch (1843-1910) was a German physician. He was the foremost to directly prove the responsibility of microorganisms in causing diseases. He established the relationship among Bacillus anthracis and the disease it causes, anthrax.

5) Koch's hypotheses are as follows:

The suspected disease-causing organism must be present in all cases of the disease and absent from the healthy animals.

a) The suspected organism should be cultivated in a pure culture away from the body of animals.

b) The isolated organism should cause the disease if inoculated to a healthy susceptible animal.

c) The organism should be re-isolated from these experimental animals and culture again in the laboratory after which it must still be similar as the original organism.

Discovery of Microbial Effects on Organic and Inorganic Matter:

1) Martinus Beijerinck (1851-1931)

a) Martinus Beijerinck was a lecturer at the Delft Polytechnic.

b) He isolated the primary pure culture of numerous soil and aquatic microorganisms, comprising sulphate reducing and sulphur oxidizing bacteria, nitrogen fixing root nodule bacteria.

c) He explained the primary virus and the fundamental principles of the virology.

2) Sergei Winogradsky (1856-1953)

a) He introduced the concept of chemo-lithotrophy, (that is, the oxidation of inorganic matter). He worked with soil bacteria and discovered they could oxidize iron, sulphur and ammonia to get energy. He as well examined anaerobic nitrogen fixation and cellulose decomposition. He published numerous scientific papers and a main monograph, Microbiologic du sol (that is, Soil Microbiology).

b) Beijerinck and Winogradsky established the utilization of enrichment cultures and choosy media.

Era of Molecular Microbiology:

Started in the year 1970.

a) Advancement in the acquaintance of bacterial physiology, genetics and biochemistry.

b) Genetic manipulation that comprises the transfer of DNA from one organism to other or a bacterium and the proteins encoded through the DNA harvested led to the growth of the field of Biotechnology.

c) DNA series revealed the phylogenetic (that is, evolutionary) relationships among bacteria which led to the revolutionary new theories in the microbial systematic.

d) In the year 1990, DNA sequencing gave birth to the field of genomics.

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