Major contributions

1. Germ theory of disease
   • Pasteur showed that microorganisms cause many processes previously attributed to spontaneous generation or “bad air.”
   • His experiments helped establish that infectious diseases can be caused by specific microbes, supporting hygiene, sanitation, sterilization, and later antiseptic surgical practice.
2. Disproved spontaneous generation
   • Using swan-neck flask experiments, he demonstrated that sterilized broth remained free of microbial growth unless contaminated by particles from the air.
   • This showed that life does not routinely arise from nonliving matter under ordinary conditions.
3. Pasteurization
   • He developed controlled heating of liquids to kill or reduce harmful microorganisms without greatly altering the product.
   • Pasteurization was first applied to wine and beer and later became central to the safety of milk and other foods.
4. Fermentation
   • Pasteur proved that fermentation is caused by living microorganisms such as yeasts and bacteria, rather than being simply a chemical decomposition.
   • This improved brewing, wine-making, and food preservation.
5. Vaccination
   • He developed the concept of attenuated vaccines, using weakened microorganisms to induce protection.
   • His notable work included vaccines for:
     • chicken cholera
     • anthrax
     • rabies
   • The rabies treatment given to Joseph Meister in 1885 was a landmark in preventive medicine.
6. Silkworm disease
   • He identified microbial causes of diseases devastating French silkworm production and advised measures to prevent spread, saving an important industry.

Legacy