HISTORICAL ASPECTS OF MICROBIOLOGY

INTRODUCTION

The history of microbiology is the story of men and women who developed a technique, a tool or a concept that was generally adopted in the studying of microorganisms. It is also the history of events and metamorphosis of microbiology as a science. In this unit we will be studying the stages in the development of the science of microbiology, some early scientists and their contributions to the field of microbiology.

Discovery of Microorganisms 

The advent of the microscope permitted the studying of microorganisms. The first microscopes were simple ground glass lenses that magnified images of previously unseen microorganisms. Among the first to observe this previously unseen and invisible microbial world were Robert Hooke and Anthony Van Leeuwenhoek.

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

* He coined the term “cells” to describe the “little boxes” he observed in examining cork slices with a compound microscope.
* He was the first to make a known description of microorganisms.
* He made microscopic observation and the earliest description of many fungi.
* Various species of fungi were clearly identified in his drawing and recorded in his book Micrographia.

Fig. 1: Robert Hooke’s Detailed Diagram of Fungi made in 1667 Source: Microorganisms in our World by Atlas R. M. (1995)

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 over 100 simple microscopes each capable of magnifying an image about 300 times. By using simple microscopes, he observed microscopic organisms which he called ‘animalcules’.

He discovered bacteria in 1676 while studying pepper water infusion and reported his observations in a series of letters to Royal Society of London which published them in 1684 in English translation.


He made sketches of the different shapes of bacteria.
He was the first person to publish extensive and accurate observations of microorganisms.
He is known as the father of bacteriology

(a) (b) 

Fig. 2: (a) Antony Leeuwenhoek (1632-1723) Holding one =of his Microscopes

(b) Leeuwenhoek’s Microscopes and some of the Sketches of Bacteria from Human Mouth
Source: Microorganisms in our World by Atlas R. M. (1995)

After Van Leeuwenhoek’s death, the study of microbiology did not develop rapidly because microscopes were rare and interest in microorganisms was not high. Scientists then were debating the theory of spontaneous generation.

 The Spontaneous Generation Conflict

The concept spontaneous generation states that living organisms could develop from non-living matter. The proponents of the concept of spontaneous generation claim that living organisms could develop from non living or decomposing matter.

1.  Francesco Redi (1626-1697) challenged this concept by showing that maggots on decaying meat came from fly eggs deposited on the meat, and not from the meat itself. · He carried out a series of experiments on decaying meat and its ability to produce maggot spontaneously. · He placed meat in three different containers, one was not covered, and the second was covered with fine gauze to exclude flies. · Flies laid eggs on the uncovered meat and maggots developed. · The two other meats did not produce maggots. Spontaneously, flies were attracted to the gauze-covered container and laid their eggs on the gauze, these later produced maggots. Hence, it become evident that the generation of maggots resulted from the presence of fly eggs and that meat (a non-living matter) did not spontaneously generate maggots as previously believed.
2.  Louis Jablot (1670) conducted an experiment in which he divided a hay infusion that had been boiled into two containers: a heated container that was closed to the air and a heated container that was freely open to the air. Only the open vessel developed microorganisms. This further helped to disprove abiogenesis.
3. John Needham (1713-1781) showed that mutton broth boiled in flasks and then sealed could still develop microorganisms, which supported the theory of spontaneous generation. 
4.  Lazzaro Spallanzani (1729-1799) showed that flasks sealed and then boiled had no growth of microorganisms, and he proposed that air carried germs to the culture medium. He also commented that external air might be needed to support the growth of animals already in the medium. The latter concept was appealing to supporters of spontaneous generation. 
5.  Louis Pasteur (1822-1895) was a Professor of Chemistry. He devised a series of swan necked flasks known as Pasteur-flasks, filled the flasks with broth and heated the broth to sterilisation. After cooling, the flasks were opened to the air, but bends on the neck of the flasks prevented microorganisms from falling on the broth and contaminating it rather the microorganisms fell on the neck of the bottle. Pasteur proved that no growth occurred because dust and germs were trapped on the wall of the curved necks. If the neck were broken, growth will occur. By these experiments he disproved and defeated the theory of spontaneous generation. Figure 3 shows the defeat of spontaneous generation. 

Fig. 3: The Defeat of Spontaneous Generation - Pasteur’s Experiment with the Swan- Necked Bottles Source: Amoebamike.wordpress.com 

Apart from the defeat of the concept of spontaneous generation,
· Pasteur’s work led to an effective sterilization method which involve holding juices and milk at 62.8OC OF) (145for 30 minutes known as Pasteurization.
· He discovered that alcoholic fermentation was catalyzed by Living Yeast Cells.
· He developed vaccines for the diseases anthrax, fowl cholera and rabies between 1880 and 1890.
· As a result of his research on rabies, he became a legend and the French government built the Pasteur Institute in Paris in 1888. It was originally established as a clinical centre for treating rabies,
but is now a major biomedical research centre for antiserum and vaccine production.
· He postulated the Germ Theory of Disease which states that microorganisms are the cause of infectious diseases.
· Pasteur’s work ushered in the Golden Age of Microbiology disease was caused by a fungus.

2. M. J. Berkerley (ca. 1845) demonstrated that the great potato blight of Ireland was caused by a fungus.
3. Joseph Lister (1872-1912) developed a system of surgery designed to prevent microorganisms from entering wounds. He implemented the use of sterile surgical instrument, and used
carbolic acid (phenol) during surgery and on wound dressings.
 4. Robert Koch (1843-1910) Robert Koch was a German physician. He was the first to directly
prove the role of microorganisms in causing diseases. He established the relationship between Bacillus anthracis and the disease it causes, anthrax. Using mice as experimental animals, he demonstrated that when a small amount of blood from a diseased mouse was injected into
a healthy mouse, the healthy mouse quickly developed anthrax. From this work he developed Koch’s postulates.
5. Koch’s postulates are The suspected disease-causing organism should be present in all cases of the disease and absent from healthy animals.
· The suspected organism must be cultivated in a pure culture away from the animal body.
· The isolated organism must cause the disease when inoculated into a healthy susceptible animal.
· The organism must be re-isolated from these experimental animals and culture again in the laboratory after which it should still be the same as the original organism.

Fig. 4: Diagrammatic Illustration of Koch’s Postulate 

Using these principles, Koch discovered causative organisms of anthrax (1876), tuberculosis (1882) and cholera (1883).
· He was the first to grow bacteria on solid culture media to get pure culture; hence he developed the pure culture concept and developed different solid media.
· Koch’s discovery of solid culture media and pure culture concept supplied the most needed tools for the development of microbiology as a field of science.
· For his contribution on tuberculosis, he was awarded the 1905 Nobel Prize for Physiology or Medicine.

Today, “Molecular Kosh’s postulates” have been established in light of advances in the molecular biology of pathogenic microbes.

6. Edward Jenner (ca. 1798) used a vaccination procedure to protect individuals from smallpox.

7. Emil Von Behring (1854-1917) and Shibasaburo Kitasato (1852- 1931) induced the formation of diphtheria tetanus antitoxins in rabbits which were effectively used to treat humans, thus demonstrating humoral immunity.