Origin of life – Redi and Pasteur experiments

For a long time the origin of life was unknown and many scientists believed in the theory of abiogenesis .

According to abiogenesis, living beings were the result of spontaneous generation from an active principle. This theory admitted, for example, that a rat could emerge from a shirt soiled with human sweat along with some wheat germ.

To prove that this theory was wrong,  many scientists tried to experiment and postulate theories, including Redi and Pasteur.

Redi experiment

The Italian  Francesco Redi (1626-1697) was a very questioning doctor and scientist. He was one of the first to raise the hypothesis that the theory of abiogenesis would not be correct.

Redi carried out an experiment using some bottles, meat and gauze. He put a piece of meat in all the bottles. One bottle was well capped, another was left open and another was covered with very thin gauze.

After some time, he observed that:

  • There were no larvae in the capped bottle, which Redi called worms.
  • In the open jar there were many larvae that later became new insects.
  • Insects were flying over the gauze flask and they laid eggs in the gauze. From these eggs emerged larvae that tried to pass through the gauze attracted by the smell of the meat.

After this experiment, Francesco Redi concluded that life could only arise from another pre-existing life and had his hypothesis accepted by other scientists, thus creating the theory of biogenesis .

From then on, abiogenesis began to lose credibility in the scientific community. However, the origin of microorganisms as bacteria was still a mystery as scientists did not believe that beings so small could reproduce.

Biogenesis – Redi Experiment

Pasteur experiment

For almost 2 centuries, Redi’s ideas were the only ones proven in the theory of biogenesis.

It was only in the middle of the 19th century that Louis Pasteur (1822-1895), a French scientist, was able to prove definitively that all living beings, including microorganisms, originated from other living beings.

In 1860, the French Academy of Sciences offered a prize to anyone who could prove the origin of the microorganisms and it was then that Pasteur carried out his experiment.

He used glass jars with stretched necks, some straight and others curved in the shape of a “swan neck”, so that the air could enter freely.

Pasteur created a nutritious broth made with water, sugar and fungi in suspension. He put some of the broth in each bottle and boiled it until steam came out of the bottlenecks and all the microorganisms in the broth were dead. Then he left the bottles to cool to room temperature.

After observing a few days, Pasteur realized that in the flasks with a straight neck, microorganisms had appeared in the nutrient broth. On the other hand, the flasks with the neck of a swan neck had nothing, although they also had an air intake available.

He then decided to break the neck of some bottles without contamination and realized that after a few days they were also full of microorganisms in the broth.

Biogenesis – Pasteur’s experiment.

This experiment showed that the organisms were present in the air and that, when they came into contact with the nutrient broth, they had an adequate means to reproduce.

The flasks with curved neck functioned as a filter for the microorganisms that were trapped in the curves and did not come into contact with the nutrient broth.

It was proved that, even though it was boiled, the broth still served as a source of nutrients for the development of living beings, that is, it did not lose the “vital force” defended by adherents of abiogenesis.

From then on, the theory of biogenesis was proven, completely burying the theory of abiogenesis.

Pasteur’s experiments also brought many advances in medicine, as the principle of killing microorganisms by raising the temperature began to be used in hospitals, drastically reducing the spread of infections.

Even today, these principles are used in the food industry to remove microorganisms from food in a process called pasteurization.

Curiosity

Did you know that the original bottles from Pasteur’s experiment, which had a curved neck and were not contaminated, can be seen at the Pasteur Institute in Paris? And even after centuries, they still remain uncontaminated.

 

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