The History of Microbiology is a fascinating one. If you are into learning Microbiology and knowing a bit of history along with it, do read on to know more.
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Germ theory is the theory of biology that discovered the reason for causing illness. Before establishing the germ theory, the old human civilizations thought we get sick because of punishment of god. People also used to believe that smelling bad odour makes us sick. This disbelief prevented humanity to resolve the mystery of falling sick. Girolamo Fracastoro (Italian Physician) was the first person to propose the theory of contagion. He proposed that the contagious disease are caused by minute bodies (seed like) which are transferred from one body to another (now we called it as germs)
How did life start on earth?
People believed that life started on earth from non living matter, this concept was called as Abiogenesis or spontaneous generation.
Aristotle, the great philosopher also believed in spontaneous generation theory (384–322 BC). Aristotle favoured spontaneous generation theory because of his observation of sudden appearance of fishes and he believed that they were made from muddy sediments present at the bottom the river. Similar observation was for frogs, which used to appear suddenly in rainy season or during flood.
In 17th century, Jan Baptista Van Helmont , conducted an experiment, where he kept a shirt and wheat grain together at one place for 21 days. After 21 days, he observed mouse and he concluded that mouse came from wheat kernel. And hence, he believed in spontaneous theory or abiogenesis.
This spontaneous theory was first challenged by Francesco Redi in 1668. He conducted series of experiments on decaying meat and appearance of flies. He took three containers, in which he placed meat. He covered first container with cloth, second was tightly sealed and third container was left open intentionally. He observed flies laid eggs over the uncovered meat which later developed maggots (the larvae of flies). The second container which was covered with cloth also attracted by flies and flies laid eggs on the cloth, developing maggots. Francesco Redi did not observe any flies or maggots near the container which was tightly sealed.
Francesco Redi analysed his observation and concluded that maggots are produced only where eggs are laid and hence the origin of life of maggots is not spontaneous. His observation and conclusion confronted the spontaneous generation believers.
In 1748, John Needham boiled the mutton broth and then tightly plugged the flask. He kept this flask for few days, and then he observed that the flasks had become cloudy. When he noticed that a single drop of cloudy broth has numerous microscopic organisms. He concluded that these microscopic organisms are spontaneously produced from mutton broth, and hence he was the believer of Spontaneous generation.
John Needham’s experiment, observation, and conclusion were challenged by Lazarro Spallanzani’s experiment.
Lazarro Spallanzani repeated John Needham’s experiment with the difference that he boiled the broth by sealing and boiling it for a longer duration. Revising the two steps of Needham’s experiment resulted in a different observation. The broth of Lazarro Spallanzani remained clear and hence no growth was observed. He concluded that life does not start spontaneously, and hence he believed in non spontaneous generation theory (1765-1776). Lazarro Spallanzani proposed that John Needham’s flask became cloudy because his flask was open while boiling during which the microbes from air were introduced into the broth making it cloudy.
Theodor Schwann was curious to search for truth, and he conducted an experiment to quench his thirst of the quest between the years 1834 and 1838. He exposed the boiled/sterilised broth to heated air. He continuously heated the neck of the flask through which air enters it. Continuously heating turned the neck into hot red. When the air enters through this hot red neck it becomes sterile. He concluded that air contains microscopic organism which make the broth sterile, and hence be believed that life started non spontaneously.
This controversy divided the intellectual world into spontaneous and non spontaneous believers. Everyone was on a quest to seek the truth. So far, the experiments conducted by spontaneous and non spontaneous believers were not able to reach the truth. The chapter in the history of microbiology gave rise to new discoveries, some of which altered the course of human civilization.
In 1859, Louis Pasteur conducted two experiments. In the first experiment, he used cotton to filter the air. He observed small plant spores like structure on the used cotton. When he placed this cotton in sterile media, he found a growth of microscopic organisms. In the second experiment, he used his self-invented swan neck flask. He placed media in the swan neck flask, boiled the media to make it sterile, and allowed it to cool. He did not observe any growth in the flask. He also observed that if the neck was broken, the media became cloudy, and microscopic organisms appeared. He concluded that the design of swan neck caused dust and microbes to settle on its wall thus allowing the sterile air to enter. With this, the non-spontaneous theory won the debate. Pasteur’s two experiments finally resolved the parley of spontaneous and non spontaneous generation theory in the year 1861. This ushered as a new chapter in the history of Microbiology.
Robert Hooke was the first person to publish his microscopic observation in the form of drawing to the Royal Society of London in the year 1665. His observation was compiled to form a book known as Micrographia. In this book, he finely drew his minute observations of fungus mucor by using his primitive microscope. Robert Hook also shared the knowledge and procedure for constructing the microscope.
Discovery of Microorganisms:
The history of Microbiology would be incomplete without mentioning Antonie Van Leeuwenhoek, the Father of Microbiology.
Antonie Van Leeuwenhoek drew inspiration from Robert Hooke’s contribution. The book Micrographia ignited Anton Van Leeuwenhoek’s curious mind. Probably, Leeuwenhoek had built his amateur microscope from the information shared in Micrographia. Professionally, Anton Van Leeuwenhoek was a draper, and used the microscope to check the quality of cloth. He used his spare time in grinding the lenses of the microscope. His hobby and passion led him to build efficient lenses which could magnify the object upto 50 to 300 times. Out of curiosity, Anton van Leeuwenhoek used this microscope to observed bees, animal sperm cells, plants, blood, teeth plaque, and water. He maintained the records of all his observations. From 1673, he started sending his observations in the form of letters to the Royal Society of London. He named the microscopic cells as Animalcules. Anton van Leeuwenhoek was the first person to see a microorganism which led to the foundation of Microbiology subject, and is rightly called as the Father of Microbiology. Observation of Microorganisms and claiming its existence by Anton van Leeuwenhoek supported the non spontaneous theory.
The Germ Theory was an important milestone in the history of microbiology.
Till now we knew that our ancestors used to believe that humans get sick when they smell bad odour or poisonous vapour (called as miasmas) or when god punishes. That was about to change, because during the same timeline, there were few people who did not believe it. Hence, began the controversial debate yet again, about the reason for getting sick.
In 1835, Agostino Bassi was working on silk worm disease and he found that this disease was caused by fungi. He proposed that the other diseases might have also been caused by such microorganisms.
In the similar line, M. J. Berkely was working on potato blight and his studies showed that the water mold is the causative agent (1846 to 1851).
During the same timeline, the wine Industry was complaining about spoilage of wine taste. People believed that the conversion of sugar to ethanol is due to the chemical instability of sugar. The Industries were not able to resolve it due to which they were in loss. The Industrialists approached Pasteur for help. Pasteur had research experience in sugar fermentation. He knew that the sugar fermentation to wine or alcohol is conducted by yeast. When he studied the spoiled wine sample, he found that the wine was contaminated with bacteria. These bacteria were producing acid which was spoiling the wine taste. The spoiling of wine is regarded as an example of germ theory, because it is considered as a disease. Later to decontaminate the wine, Pasteur suggested the use of heat for killing the microbes and this process till date is called as Pasteurization (1865).
Before the discovery of microbes, doctors and surgeons were unaware of microbes and their pathogenicity. And therefore, no precaution or sterilization was carried on during any surgery. The surveys had found that people were dying more because of infection caused during the surgery.
Joseph Lister was a surgeon and he followed the Pasteur’s published papers (1860-1869). Because of his readings he became aware about the microorganism and its source (air). He applied his learnt knowledge in the field of Sciences. He started sterilizing all the surgical instruments before conducting surgery. He initiated disinfecting and decontaminating the wound. For sterilization and disinfecting, he used heat and phenol. Such application of interdisciplinary knowledge revolutionised the protocol of surgery. Joseph Lister observed that implementing Sterilization in surgery reduced the mortality rate from 50% to 15%.
By this time, scientists knew that microorganisms were responsible for contamination and infection. But no evident research had come so far to demonstrate above observations. A German physician Robert Koch started working on anthrax when he found that cattles of his village are dying because of anthrax. He isolated the blood samples from infected and healthy cattle, and observed it under microscope. He found small minute bodies or microbes in the blood of infected cattle, whereas it was absent in the healthy ones. He isolated those microbes and grew it in nutritional liquid. He found that these microbes were growing and multiplying. He discovered that the microbes could also be grown outside the host. When these microbes were again inoculated in the healthy mice, the healthy mice got anthrax. This series of experiments demonstrated the relation between Bacillus anthracis and anthrax. Koch presented his observation in the form of postulates which came to be known as Koch Postulates
- The microorganisms must be present in every case of the disease but absent from healthy organisms.
- The suspected microorganisms must be isolated and grown in a pure culture.
- The same disease must result when the isolated microorganism is inoculated into a healthy host.
- The same microorganisms must be isolated again from the diseased host.
The History of Microbiology is not only rich in its existence, but also in its constant struggle to find out the truth and bringing it in the public domain.
Activity for the History of Microbiology:
- Where else is Pasteurization used and how is it done?
- Understanding the Koch experiment, draw a flowchart of his experiment.
- Prepare a timeline of the entire scientists involved in resolving spontaneous – non spontaneous theory and germ theory controversy.
- According to the chapter write down the experiment of given scientists:
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