Contribution of Louis Pasteur in Microbiology
Contribution of Louis Pasteur in Microbiology

Contribution of Louis Pasteur in Microbiology

There are many tremendous contribution of Louis Pasteur in Microbiology as well as in Chemistry (Crystallization), which plays great role in medical field.

Early life of Louis Pasteur

Louis Pasteur was born on December 27, 1822 in France to a Catholic family of a poor tanner. Pasteur entered primary school in 1831. He was an average student in his early years, as his interests were more in fishing and sketching. He drew many pastels and portraits of his parents, friends and neighbours. Pasteur attended secondary school at the College d’Arbois.

In 1839, he entered the College Royal at Besancon to study philosophy and earned his Bachelor of Letters degree in 1840.

He was appointed as professor of physics at the College de Tournon and simultaneously started his research in crystallography in 1846. In 1847, he submitted his two thesis, one in chemistry and the other in physics.

Pasteur was appointed professor of chemistry at the University of Strasbourg in 1848. In 1867, the Ecole Normale’s laboratory of physiological chemistry was created at Pasteur’s request, and he was the laboratory’s director from 1867 to 1888. In Paris, he established the Pasteur Institute in 1887, in which he was its director for the rest of his life.

The Contribution of Louis Pasteur in Microbiology are as follows:

There are many excellent contribution of Louis Pasteur in Microbiology which is very important for medicinal field, some of them are as follows:

1. Disapproving the theory of spontaneous generation

The theory of spontaneous generation states that life originated from non-living things in a spontaneous manner. Many well-known scholars like Aristotle and John Needham were in favor of this theory. Whereas, there are some scholars who were against the theory of spontaneous generation like Francesco Redi and Lazzaro Spallanzani.

Redi and Spallanzani had provided some evidence against spontaneous generation in the 17th and 18th centuries, respectively. Spallanzani’s experiments in 1765 suggested that air contaminated broths with bacteria. Pasteur was also against these theory and he performed several experiments to disapprove spontaneous generation out of which two of them has been explained below:

Experiment 1.

  • Pasteur boiled infusion in the flask, heated the glass neck and drew them out into long, curved tubes open at the end. Air could enter the flask without any of the treatments.
  • Airborne microorganisms could also enter the neck of the flask, but they became trapped in the curves of the neck and never reached the infusion.
  • So the infusion remained sterile for longer period unless a flask was tipped/tilted so that the infusion flowed into the neck and then back into the flask.
  • So the manipulation allowed microorganisms trapped in the neck to enter into the infusion, where they could grow and cause the infusion to become cloudy.
  • This showed that the living organisms that grew in such broths came from outside, on dust, rather than spontaneously generating within the liquid or from the action of pure air.
Swan neck flask experiment by Louis Pasteur

This is another version of the same experiment where the neck is removed from the flask so the bacteria present in the air can easily enter into the infusion and this leads to the growth of microorganisms in short time.

Experiment 2.

  • In another experiment Pasteur filtered air through three cotton plugs, he then immersed the plugs in sterile infusions.
  • After few hours the microbial growth was observed in the infusion. So he demonstrated that the microbial growth occurred in the infusion is from the organisms trapped in the cotton plugs.

These were some of the most important experiments of Pasteur for disproving the theory of spontaneous generation. 

2. Fermentation

The contribution of Louis Pasteur in Microbiology – Fermentation. Pasteur was eager to investigate fermentation while working at Lille. In the mid-1850s, he undertook a series of studies on alcoholic fermentation at a local distillery. He learned about many aspects of fermentation, including the compounds that cause milk to sour. In 1857 Louis Pasteur concluded that microorganism causes fermentation and that specific kinds of microbes causes specific types of fermentation. Also, he concluded that the living cells were causing the alcohol to form from the sugar.

Pasteur also wrote about alcoholic fermentation. It was published in full form in 1858. Jons Jacob Berzelius and Justus von Liebig had proposed the theory that fermentation was caused by decomposition. Pasteur demonstrated that this theory was incorrect, and that yeast was responsible for fermentation to produce alcohol from sugar.

In 1861, Pasteur observe that less sugar fermented per part of yeast when the yeast was expose to air. The lower rate of fermentation aerobically became known as the Pasteur effect.

3. Pasteurization

One of the biggest contribution of Louis Pasteur in Microbiology is Pasteurization. Pasteur’s research also showed that the growth of micro-organisms was responsible for spoiling beverages, such as beer, wine and milk. With this established, he invented a process in which liquids such as milk were heated to a temperature between 60 and 100 °C. This killed most bacteria and moulds already present within them. Pasteur and Claude Bernard completed tests on blood and urine on April 20, 1862. Pasteur patented the process, to fight the “diseases” of wine, in 1865. The method hence known as “pasteurization”.

Pasteurization was first used to save the French wine industries from the problem of contamination. Soon the process was also apply to milk and beer. Pasteurization continues to be use widely in the dairy industry and other food processing industries to achieve food preservation and food safety.

4. Silkworm Disease

In 1853, two diseases called pebrine and flacherie had been infecting great numbers of silkworms in southern France, and they were causing huge losses to farmers. After that the French silkworm industry was being drastically destroy by these two infectious diseases which were killing a great number of silkworms. In 1865, Louis Pasteur accepted a request to investigate the problem though he knew nothing about silkworms.

Pasteur successfully identified the organisms that had caused a mysterious disease in silkworms and endangered the French silk industry. He was able to save the silkworm industry through a method of prevention of contamination of healthy silkworm eggs. Pasteur also showed that the disease was hereditary. The method was soon taken by silk producers all over the world and is still using in silk producing countries.

5. Germ Theory of Disease

The germ theory of disease states that certain diseases are caused by specific germs or infectious agents.

After working on fermentation and pasteurization, Pasteur gathered better understanding of germ theory.  In the 1800s, this idea was not widely accepted, and it took a series of experiments and hard work for Pasteur to prove that air contains infinitely small living organisms, and that these organisms are responsible for diseases.

He was also known as “Father of Germ Theory” and also known as “Father of Bacteriology” as his many experiments showed that disease could be prevented by killing or stopping germs, thereby directly supporting the germ theory and its application can be now widely seen in clinical medicine.

6. Vaccine or Immunization

The contribution of Louis Pasteur in Microbiology – Vaccines: After studying microbes and how they cause disease, another important contribution of Pasteur in the field of medicine is the discovery vaccine for some of the fatal diseases. He developed vaccines against four deadly infections.

Chicken cholera vaccine

Louis Pasteur’s first important discovery in the study of vaccination came in 1897 and was regarding the disease chicken cholera. After accidentally exposing the chickens to an attenuated culture of the disease, he observed that they became resistant to fully virulent strains. Since then, Pasteur directed all his energy on the problem of immunization and applied this principle to several other diseases.

Chicken cholera vaccine experiment


Pasteur wanted to apply the principle of vaccination to anthrax. He prepared attenuated cultures of the bacillus (causative agent of anthrax) after determining the conditions that led to the organism’s loss of virulence. In the spring of 1881 he obtained financial support, mostly from farmers, to conduct a large-scale public experiment of anthrax immunization. The experiment took place in Pouilly-le-Fort, located on the southern outskirts of Paris. Pasteur immunized 70 farm animals, and the experiment was a complete success.

 The vaccination procedure involved two inoculations at intervals of 12 days with vaccines of different potencies. One vaccine, from a low-virulence culture, was given to half the sheep and was followed by a second vaccine from a more virulent culture than the first. 

Two weeks after these initial inoculations, both the vaccinated and control sheep were inoculated with a virulent strain of anthrax. Within a few days all the control sheep died, whereas all the vaccinated animals survived. This convinced many people that Pasteur’s work was indeed valid.


In 1885, Pasteur was assigned the task of generating a vaccine for rabies (i.e., hydrophobia) a fatal disease of man caused by bites of mad cats, dogs, and wolf. When he began his work on rabies, it had already been discovered that the microbe that caused the disease was present in the saliva of its victims. Because madness is one of the symptoms of rabies, Louis know that the microbe must attack the central nervous system (CNS).

He first studied the saliva of animals and humans who died because of rabies and confirmed the presence of microscopic microbe in their saliva. Then he came to known that the microbe is a virus, too small to be seen under microscopes obtainable at his time and not grown-up in laboratory. Therefore he employed the saliva of mad dogs to inject rabbits. The spinal cord and brain of artificially injected rabbits were eliminated, dried, powdered and suspended in glycerine. By injecting such preparation, Pasteur immunized dogs against rabies.

Pasteur cured a boy Joseph Meister bitten by a mad wolf in an identical way and saved him. Therefore vaccine against rabies was developed and saved thousands of lives.

 Swine erysipelas

In 1882, Pasteur sent his assistant Louis Thuillier to southern France because of an epizootic of swine erysipelas. Thuillier identified the bacillus that caused the disease in March 1883. Pasteur and Thuillier increased the bacillus’s virulence after passing it through pigeons. Then they passed the bacillus through rabbits, weakening it and obtaining a vaccine. Pasteur and Thuillier incorrectly described the bacterium as a figure-eight shape. Roux described the bacterium as stick-shaped in 1884.


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