A Search For Better Health Topic 4 : Pasteur and Koch. Biology in Focus, HSC Course Glenda Childrawi , Margaret Robson and Stephanie Hollis. DOT Point(s) . describe the contribution of Pasteur and Koch to our understanding of infectious diseases. world.edu. Introduction.
Biology in Focus, HSC Course
Glenda Childrawi, Margaret Robson and Stephanie Hollis
In the second half of the nineteenth century there was a revolution in microbiology, primarily due to the research of Louis Pasteur and Robert Koch. Working separately, they were able to make an invaluable contribution to our understanding of infectious disease.
Although they each used aspects of the other’s work in their own research, the degree of collaboration and communication was minimal as they did not get on with each other.
Prior to the work of Pasteur, Koch and others, the explanation for the cause of disease and decay was the theory of spontaneous generation. This involved the idea that life, such as the maggots that were present in rotting flesh, arose spontaneously from nonliving things.
Pasteur was able to disprove this theory and establish the ‘germ theory of disease’. This theory states that germs (microbes) cause disease and that all micro-organisms come from pre-existing microorganisms.
Louis Pasteur (1822–1895) was born in France, studied chemistry and received many awards for his work relating crystal structure to optical activity. Although not his original area of study, he was credited with creating the science of microbiology and made invaluable contributions to the understanding of infectious disease.
He also found that other micro-organisms were responsible for the souring of the alcohol produced.
Pasteur was instrumental in finding that micro-organisms (bacteria) were the cause of wine, beer and vinegar spoilage. He discovered that the solution to the wine and vinegar problem was to heat these solutions long enough to kill the contaminating bacteria that were present after fermentation.
This was the beginning of the widely used process of pasteurisation, still used today to ensure products such as milk are free of disease-causing micro-organisms and are suitable to drink. This process was initially used in milk production to destroy the tuberculosis bacterium.
Pasteur also found that the rotting of foodstuffs was due to the activity of living organisms.
He carried out his famous ‘swan-necked flask’ experiments to gain evidence to support his theory.
These experiments involved using flasks that had long-drawn-out necks (like those of swans) that were not sealed. Meat broth was boiled in the flasks and as they cooled the air was drawn in from outside. Any microorganisms present in the air did not reach the broth as they were trapped in the narrow neck and the curve of the glass.
No bacterial or fungal growth was observed in these flasks. Bacterial growth occurred if the curve of the flask was broken off and the contents of the flask exposed to the air. Furthermore, the tipping of a flask to allow the solution in it to reach the curve where the micro-organisms were trapped resulted in bacterial growth occurring.
This added further evidence to discredit the theory of spontaneous generation. It proved that the organisms that contaminated the broth and caused it to decay must be carried in the air and not be spontaneously generated.
Pasteur’s flasks are on display at the Pasteur Institute in Paris and, after nearly 150 years, the broth in the swannecked flask is still free of bacterial growth. This classic experiment carried out by Pasteur demonstrates how theories in science can be disproved.
Pasteur investigated the cause of anthrax and, after input from the experiments of Koch, determined that the animals that were contracting the disease, even though they had no known contact with animals suffering from the disease, did so due to spores from the carcasses of animals that died from the disease. These carcasses had been buried in the fields that were grazed by healthy animals.
Pasteur, in the course of his studies of fowl cholera, also developed a way to attenuate, or weaken, bacteria so that when they are introduced into a host they could cause the body to be ready to recognise the real infection. He had produced a vaccine that prevented chickens from developing chicken cholera.
He extended this work and developed a vaccine for anthrax. His detractors were not convinced about the effectiveness of the vaccine and he was challenged to carry out a public field test. This trial was successful as all animals that were given the vaccine before being exposed to anthrax survived, and the animals that were not given the vaccine died.
The vaccine was found to be effective and its use was widely adopted.
Robert Koch (1843–1910) was born in Germany and obtained his medical degree from Göttingen.
He was an expert on bacteriological techniques and many of the techniques used today are based on Koch’s original techniques.
Koch also carried out an extensive study of the anthrax bacillus. He examined the blood of sheep that had died from anthrax and identified rod-shaped bacteria that he isolated and grew in cultures. These cultured bacteria were then injected into healthy sheep that subsequently developed anthrax.
He repeatedly showed that the anthrax spores he had obtained from the pure cultures he had grown could cause the disease in other animals and kill them. These experiments added further weight to the germ theory of disease as they showed that a microorganism grown outside the body caused a disease.
The steps that must be followed to determine if a particular micro-organism is responsible for causing a disease are known as Koch’s postulates and are given below:
One of Koch’s subsequent big breakthroughs was the discovery of the bacterium responsible for tuberculosis, Mycobacterium tuberculosis. He was also responsible for identifying the bacteria responsible for causing cholera. He travelled extensively in the latter part of his career to study diseases such as the bubonic plague and African sleeping sickness.
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