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Louis Pasteur (1822-1895, France): Pasteurisation
in 1885 (picture-alliance/akg-images)
Only a select few inventors have truly changed the way we look at the world. And through his explanations of processes in the micro world, French microbiologist and chemist Louis Pasteur helped to make the world a safer place. By proving the germ theory of disease and devising a number of methods to curb infections, Pasteur single-handedly propelled science and medicine into a new era.
In Pasteur's time, spontaneous generation - the theory that microbes like spores and fungi generate of their own accord in non-living organisms - was still a widely held belief. Pasteur took that theory apart by proving that without contact to outside particles, nothing would grow in even the most nutritious of liquids.
In his experiment, Pasteur exposed boiled broth to air in a modified Florence Flask through a filter that kept out all foreign particles - and indeed, nothing happened to the liquid. He thereby proved that fermentation and other organic processes are caused by microorganisms entering from the outside, and not by spontaneous generation from within.
This finding was also in favour of germ theory, which says that diseases are caused and transmitted by small organisms like bacteria. The implications were revolutionary - here was the reason that caused sickness, visible under a microscope.
Pasteur conducted further experiments and finally convinced all of Europe of the validity of germ theory. It earned him the title of Father of Bacteriology along with Robert Koch and Ferdinand Cohn.
Pasteur also found that by exposing organisms to weakened forms of germs, they would develop immunity. Accordingly, he found the first vaccine for rabies and made other valuable contributions to the study of immunology.
Ever the man of action, Pasteur found many practical applications for his experiments, the most famous of which is the process of pasteurisation. Using heat, pasteurisation kills off germs and mould in liquids such as milk. Although he could have been a rich man, Pasteur did not choose to patent the process, staying with his credo that "knowledge belongs to humanity, and is the torch which illuminates the world."