Germ Theory (and Louis Pasteur)

In the 19th Century People knew there was a link between dirt and disease, but could not explain the link. People explained disease as seeds. Bad seeds in the air known as miasma. In the 1850s &1860s there was a breakthrough in the cause of disease….

1. The Discovery of Micro-organisms Anthony Van Leeuwenhoek made one of the earliest microscopes. Van Leeuwenhoek discovered micro-organisms - which he called animalcules. His microscope was not as powerful as the ones we have today

2. Improved Microscopes In the 1800s purer glass produced = better lenses for microscope. 1830 Joseph Lister develops a microscope which could magnify x1000

3. Louis Pasteur proposes his “Germ theory” By 1800 some doctors were beginning to speculate about germs or micro-organisms. This was mainly due to the invention of the microscope. Old Theory: spontaneous generation Many doctors believed germs were the result of disease and not the cause of it! New Theory: germ theory Pasteur believed micro-organisms caused decaying matter. Pasteur showed you could kill the micro-organisms by applying heat - PASTEURISATION.

4. Germ Theory Pasteur proved his theory. Pasteur conducted an experiment showing that microbes in the air caused decay. 1861 published his ‘Germ Theory’

5. Micro-organisms linked to disease Pasteur showed micro-organisms made wine and beer go bad. Pasteur also proved that germs cause disease. He showed that a micro-organism could cause disease in silk worms.

Microorganisms from today!

6. Specific microorganism- bacteria linked to human disease Pasteur never showed the link between bacteria and human disease. But, Robert Koch did!

7. Robert Koch Koch took Pasteur’s work a step further. He linked particular germs to particular diseases: 1875 -identified the germ for anthrax. 1882 -discovered the germ for tuberculosis. (TB) 1883 -discovered the germ for cholera. With the development of technology he discovered microbes that had preciously been invisible to the most powerful microscopes. He even developed ways of staining the microbes with dyes so he could calculate their life span and rates of reproduction.

Microorganisms Figure 1.1