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Redi's experiment
He wanted to disprove the theory of spontaneous generation, which suggested that living organisms could arise spontaneously from non-living matter.
Lederberg's experiment involved placing sterile meat broth into two different containers, one of which was open to the air and the other was sealed. Over time, only the open container showed signs of microbial growth, while the sealed container remained sterile. This result suggested that the microbes came from the air and not from the meat. -
Needham’s rebuttal
In Needham's experiment, he heated broth to kill microorganisms and poured it into flasks. After the broth cooled, he sealed the flasks and observed living microorganisms in the broth. Needham concluded that spontaneous generation was a fact, which contradicted Redi's previous experiment that had supported the theory of biogenesis. -
Lazzaro Spallanzani
Lazzaro Spallanzani disagreed with Needham's conclusion that spontaneous generation was a fact and performed numerous experiments using heated broth. He boiled the flasks for a long time, which killed microorganisms, and observed that once the flasks were unsealed, microorganisms rapidly grew in the broth. Spallanzani concluded that spontaneous generation was false and that microbes came from contaminated air, supporting the theory of biogenesis. -
Louis Pasteur
Louis Pasteur replicated the experiment to test the theory of spontaneous generation. He designed bottles with S-curved necks and placed nutrient-enriched broth in them. He boiled the broth and observed no life in the bottle for a year. When he broke off the top of the bottlehe observed life forms in the broth within days. Pasteur concluded that contamination came from life forms in the air, not a supposed "life force," providing evidence for the theory of biogenesis.