Pasteur

• A brewery company hired him to find out why all their alcohol was going off so quickly. When he looked through a microscope, he found microorganisms growing rapidly in the beer.
• Pasteur began to suspect that the germs weren’t the product of decay, but were in fact responsible for it. He felt they may have fallen from the air into the brewery’s fermentation tanks.
• He was able prove his theory through an ingenious experiment involving capturing air in a swan neck flask, to show how decay would set into a liquid. He began by putting a nutrient rich broth, which he called the infusion into the flask. He boiled it to kill off the existing microorganisms. If the flask remained upright, microorganisms could not get into the liquid, and it remained unaffected. In comparison, if he broke the swan neck to allow microorganisms into the liquid, it would quickly go sour and bacteria would rapidly multiply.
• Pasteur exposed the flask to air across various places in France and found differences. For example, cleared, dust-free air had a lesser effect on the liquid, and city air caused more fermentation than the mountain air.
• Rather than being spontaneously generated within the broth, microorganisms already existed outside it, in the air and on dust spores.
• This led to the publication of Germ Theory in 1861.
• The theory had four parts. Firstly, that the air is full of microbes, secondly, that there are more microbes in some areas than in others. Thirdly, microbes can decay, and finally, these microbes can be killed by heating.
• The process of heating bacteria to kill it was called Pasteurisation.
• Aside from this in 1865, Pasteur also showed that germs were causing a disease that was killing the silkworms that provided for the silk industry. This led him to theorise that germs and microorganisms may also lead humans to become ill.
• The chicken cholera vaccine was actually discovered by pure chance due to a forgetful member of Pasteur’s team called Charles Chamberland.
• Chamberland was given a liquid culture containing the disease by Pasteur and was told to inject the lab’s chickens before he left to go on holiday. Of course, he forgot. When he returned, many days later, he realised his mistake, and duly injected the chickens. But they did not contract the disease. Even when they were injected with a fresh dose of the disease, the chickens did not die.
• Pasteur and his team realised that the air had weakened the germs to a point that they no longer killed but instead gave immunity. They went on to weaken other viruses, including anthrax and rabies.