Topic 4.3

In the 1860s, Louis looked into a disease that gave silkworms diarrhoea. He found that the silkworms were becoming sick because of a pathogen called protozoa. This laid the foundation for his discovery, ‘Germ Theory’ – which states that microorganisms cause disease.

One important process that emerged from germ theory is that most milk is ‘pasteurised’. This means it is heated to kill pathogens before being sold in shops. Without it, drinking milk can quite easily make people very sick. Cooking meat to kill pathogens is also a type of pasteurisation. Fermentation is also used to protect food from pathogens before storing and eating it.

Louis is also famous for the saying that ‘fortune favours the prepared mind’, inspiring scientific preparedness and innovation even today. 

Alice Catherine Evans was an American microbiologist who expanded on Louis Pasteur’s findings about germs and disease. In the early 1900s, she discovered that raw milk could transmit Brucella abortus, a bacterium causing brucellosis in humans.

Her research proved that pasteurising milk was critical to preventing this and other diseases. Initially dismissed, her findings were later universally accepted, leading to mandatory pasteurisation laws significantly reducing milk-borne infections.

Robert Koch became famous for his work on anthrax, cholera, and tuberculosis. He discovered that the anthrax microbe produced spores that lived long after an animal died. Koch also showed that these spores could develop into the anthrax germ and infect other animals. 

His best claim to fame was developing a new method for discovering the role of microorganisms in disease, known as Koch’s Postulates.

Koch’s Postulates:

1. The organism must always be present in every case of the disease. 
2. The organism must be isolated from a host containing the disease and grown in pure culture. 
3. Samples of the organism taken from pure culture must cause the same disease when inoculated into a healthy, susceptible animal in the laboratory. 
4. The organism must be isolated from the inoculated animal and must be identified as the same original organism first isolated from the originally diseased host. 

Sir Alexander Fleming received the Nobel prize – he is famous for discovering the antibiotic penicillin, which is still widely used today. 

Fleming discovered that a type of mould called penicillium happened to kill some bacteria – it was an accidental discovery.

Fleming, Howard Florey and Ernst Chain were awarded the Nobel prize in 1944.  

Marshall had a theory that bacteria caused stomach ulcers. He had an unusual way of testing this idea.

Barry decided to test his theory by growing the bacteria and then swallowing some himself. He then used a type of camera called an endoscope to take photos of his stomach. He found that after swallowing the bacteria, he developed a stomach ulcer!

In 2005, Barry Marshall was awarded the Nobel Prize.