Louis Pasteur and Spontaneous Generation

Study Notes

Pasteur and the Defeat of Spontaneous Generation

French scientist Louis Pasteur (1822–1895) revolutionized microbiology in the mid-to late nineteenth century.
Pasteur's research debunked the long-held theory of spontaneous generation.
Pasteur's initial studies focused on alcoholic fermentation, challenging the belief that fermentation was purely a chemical process.
Pasteur's research demonstrated that yeast cells, living organisms, were responsible for catalyzing fermentation.
Pasteur's experiments with spontaneous generation revolved around studying the appearance of microorganisms in putrefying food.
Pasteur's experiments demonstrated that microorganisms found in spoiling food were not generated spontaneously but originated from microorganisms present in the air and on surfaces.
Pasteur showed that if food was sterilized, meaning all microorganisms were killed, and then protected from further contamination, it wouldn't putrefy.
Pasteur used heat sterilization to eliminate contaminants from nutrient solutions and countered the claim that "fresh air" was necessary for spontaneous generation.
Pasteur's swan-necked flask experiment elegantly disproved spontaneous generation.
In this experiment, nutrient solutions were sterilized by boiling and left in flasks with bent necks. The bent necks allowed air to re-enter but trapped microorganisms from reaching the broth, preventing putrefaction.
When the necks of the flasks were broken, exposing the broth directly to the air, the broth putrefied, confirming that microorganisms from the air were responsible for the contamination.