Introduction
Diseases are caused by microorganisms which can be bacteria, fungus, viruses, etc. The theory that states that microorganisms are the reason for various diseases are the germ theory of disease. This theory was first proposed by Louis Pasteur who is famously known for cholera, anthrax and rabies vaccine as well as originating the process of pasteurization. He showed putrefaction and fermentation occur due to the presence of microorganisms that grow and flourish in the air around us.
History and Experiments
There were two archaic theories in the 17th century preceding the germ theory, which is the Miasma theory and the spontaneous generation theory. They gave the idea that living things arise from non-organic matter on earth. The latter theory was proven wrong by keeping meat and eggs in different jars in different states and conditions. One jar was kept open, while another one was tightly sealed and the third one was sealed with gauze. It was observed that the first jar got infested with maggots while nothing much happened in the second jar. It was also observed that maggots were lingering on top of the sealed gauze but not inside the jar.
Later in the 19th century, Louis Pasteur conducted experiments that later on established the germ theory. He subjected freshly boiled broth to different environmental conditions and studied the results. One vessel containing broth was kept exposed to open air using a long tube protecting it from dust particles and another vessel was kept entirely exposed without a filter. He observed that the vessel kept open without a filter showed the development of microorganisms. This led to the development of the germ theory.
Fermentation
The germ theory of disease given by Pasteur showed that microbes present in the air are the reason for the fermentation of the broth causing it to get spoiled. He also conducted further experiments on fermentation in compounds like butyric acid, lactic acid, etc. which helped develop the germ theory of fermentation.
The germ theory of fermentation states that some particular microbes are responsible for the occurrence of fermentation. This theory later proved right for diseases occurring in humans and animals as well. It was also observed that the diseases are caused by microorganisms that reside inside the body as well as which are found outside in the surrounding environment.
The germ theory of disease led to the recognition of immunity protection against some types of pathogens.
Koch’s Postulates
Robert Koch conducted experiments on anthrax which was isolated from the disease host. He made some observations that led to the development of four postulates which are given as follows:
The disease-causing microbe has to be found in the diseased person and not in a healthy person showing no signs of the disease.
The microorganisms have to be isolated from the diseased person to be cultured next.
The cultured microorganisms introduced in a healthy person should cause the same disease.
The fourth postulate states that the samples collected from the voluntarily infected person must be the same as that of the cultured batch of microbes that was originally isolated from the host.
Examples of Microbes
There are several disease-causing germs, some of which can be viruses or protists. Diseases caused by these germs are termed infectious diseases.
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Solved Examples
1. Who Proposed the Germ Theory of Disease?
Ans: Louis Pasteur proposed the germ theory in the 1850s when he conducted experiments that proved the presence of microorganisms and their role in fermentation and other processes.
Did You know?
"Germ" may not just mean a bacterium but can refer to any microorganism or pathogens that are non-living but may become a cause of disease. Examples of such pathogens are prions, viroid, protists, viruses. Diseases that are caused by such pathogens are called infectious diseases. Although a pathogen may become the principal cause of a disease, other factors need to be considered. Hereditary and environmental factors often influence the severity of the disease.
FAQs on Germ Theory Of Disease
1. State the germ theory of disease.
The germ theory of disease states that certain diseases are caused by the attack of some specific microorganisms on the human body which are found either inside or outside the body, in the surrounding environment. This theory was given by Louis Pasteur who conducted various experiments on a growth medium left in different environmental conditions and observed.
2. What are the principal causes of disease?
Germs and microbes found in the environment and inside the human body are mostly responsible for diseases in humans. Other factors like hereditary ailments, diseases relating to anomalies in the DNA and environmental conditions around a human being are also responsible for certain diseases.
3. Why is germ theory important?
The germ theory helped in understanding the causes of various diseases and attempting to prevent them based on the knowledge of the microorganisms.
4. What was the spontaneous generation of theory?
The spontaneous generation theory, proved by Francesco Redi in the 19th century, states that all living things arise out of non-organic matter.
5. Explain the Germ Theory of Disease.
The currently accepted scientific theory that explains many diseases is the germ theory of disease. This theory states that germs, also called pathogens, which are microorganisms, are responsible for causing various diseases among individuals. They are called microbes because their size is so small that they are imperceptible without the use of magnification or a microscope. These organisms invade other plants and animals to grow and reproduce, which causes diseases in their hosts. This theory replaced the earlier Miasma theory that dominated the theory of disease transmission before. Robert Koch and Louis Pasteur are mainly responsible for the development of this theory.
6. How did Koch and Pasteur Contribute to the Germ Theory?
In 1861, Pasteur published the germ theory after experimentation and proved that bacteria caused diseases. Robert Koch in Germany also began pursuing the same idea and began isolation of specific bacteria causing various diseases like cholera. Koch discovered antibodies helped in fighting pathogens and hence ailments. However, it was the French Louis Pasteur who came up with the first vaccines since Jenner, with vaccines for rabies, anthrax and chicken cholera. Koch was a pioneer in using stains to observe bacteria more clearly under a microscope. His assistant, Julius Petri, devised the use of the Petri dish to help in this process.
