Science & People

Louis Pasteur | His life, inventions, and great contributions to science

When Louis Pasteur died in 1895, he was a national hero in France and became internationally famous as well. The public got to know him most with his work on the prevention and treatment of infectious diseases in the last years of his life. But for the scientific community, he was the person who created the field of stereochemistry, revealing the biological nature of fermentation, overturning the doctrine of spontaneous generation, explaining the biological nature of diseases, helping to establish the microbe theory, and demonstrating the economic and social benefits of experimental laboratory research in many fields.

Although Pasteur's position was partly based on his own advertising, it was actually due to the wide-ranging achievements of microbiology in its theory and practice. Gerald Geison wrote for him: "While he often exhibits great courage and a powerful imagination, the characteristic features of his work, in general, are clear mindset, extraordinary experimental skills, perseverance, and even stubbornness."

Who is Louis Pasteur?

Pasteur was born in Dole, east of France, and his father was a tanner. He went to school in Arbois and Besançon, and his grades were good enough to be recommended for the entrance exams of the respected Ecole Normale Superieure in Paris. He failed the exam in 1842 but succeeded the next year. He chose physical sciences, and after completing his undergraduate education, he focused on crystallography, a new field in physics and chemistry, and completed his doctorate in a double degree.

He studied the chemical formula and the relationship between the crystalline forms of sodium tartrate. Scientists were interested in different – that is, isomorphic – chemicals with very similar chemical structures. Salts of tartaric acid were of particular interest. Because with dimorphism, the microscope revealed that the two forms are mirror images of each other. Of course, luck played a role: crystallization is extremely heat-sensitive and Pasteur was working at the most appropriate time of the year. Sodium tartrate shows this asymmetry more clearly than almost any other salt. He found that crystals in natural sources have polarization properties that appear in those synthesized in the laboratory.

Through long and difficult observations, he revealed that natural crystals always have right-handed material while synthetic crystals have equal amounts of right and left material. This meant that the polarization properties neutralized each other. Five elements in this study define Pasteur's scientific style: his ability and determination to experiment, his use of the microscope, his interest in the unique chemistry of life, his best use of luck, and the great impact of his results.

In 1849, Louis Pasteur transferred to Strasbourg University as a professor of chemistry, continuing to work on asymmetry and enjoying his growing reputation. His private life changed when he married Maria Laurent, daughter of the university president. Marie provided both financial and moral support for his career. Six years later, he was appointed as the dean of the newly established Science Faculty at Lille University and moved there. He welcomed the university's mission to combine research with teaching and science practice to support the local industry. He taught lectures on bleaching, refining, and brewing, but continued his research in the field of asymmetric compounds and optical activities.

The great fermentation controversy

A drawing depicting the day Louis Pasteur and Felix-Archimede Pouchet argued
A drawing of the day Louis Pasteur and Felix-Archimede Pouchet argued.

Pasteur's great interest in the chemistry of living organisms led him to investigate fermentation and especially the role of yeast in alcohol production. In 1857, he gave a speech on lactic acid and amyl alcohol, the common by-products of bad fermentation. He argued that the asymmetric optical properties of amyl alcohol came from the fermentation process, which was related to living organisms. This was against the common idea that fermenting is a chemical process.

Returning to Ecole Normale, director of scientific research in 1860, Pasteur published his main work, which finalized the biological explanation on fermentation. It was interesting that a person trained in chemistry and physics advocated vitalism, emphasizing the uniqueness of life and the fact that life cannot be reduced to material forces. Pasteur turned his microscope from crystal structures to fermented grapes and sour milk, observing large molecules such as yeast and other ferments that were previously supposed to change shape in the process. It once again affirmed that yeast consists of living cells or microorganisms.

During the fermentation studies, there was a very famous contrast between Pasteur and Felix-Archimede Pouchet on the spontaneous generation of life. Pasteur first made a speech against the spontaneous generation in February 1860, publishing an article the following year dealing with the fact that life always derives from an earlier life. He received an award for this article. The subject of his work was leavening in liquid mixtures and deterioration of natural products. He argued that these could always generate spontaneously without contamination with live ferments.

Two scientists embarked on a scientific duel, mutual scientific results, and polemics being presented, sophisticated sterilization techniques mixed with religious inferences over whether life was constantly created. Louis Pasteur defended the general view that life was created by God in the distant past and cannot be created by simple physical force. This strife not only resulted in the consensus of the scientific community but unusually in the judgment of the committees of the French Academy of Sciences in Pasteur's favor and against spontaneous generation.

Louis Pasteur's fight against germs and disease

The microscope, other instruments and silk cocoons Pasteur used to study silkworm disease pebbles in the 1860s
The microscope, other instruments, and silk cocoons Pasteur used to study silkworm disease pebbles in the 1860s

This contrast led Pasteur to a new field, to the research of disease in animals and humans. Doctors had long thought that the development of fever and septic infections were similar to fermentation and spoilage; Thinking that these processes involve living organisms or microbes raised new questions. Of course, the link was speculative, and this was well reflected in the phrase "germ theory of diseases." The term "microbe" explained that these organisms were very diverse, very common in the environment, especially in the air, and were potentially powered by fission; The fact that it was a "theory" meant that the link that is needed to show they caused the disease still had to be proven.

Following the practical applications of the microorganism theory in fermentation and spoilage, Pasteur found that heating the wine to 50 degrees kills yeast cells and prevents spoilage. The same method is still used to prevent milk from spoiling and is called pasteurization. The most famous application of Pasteur's germ theory was the development of antiseptic methods by British surgeon Joseph Lister, who assumed that the septic infection of wounds was related to microorganism contamination leading to rotting. Lister had always given Pasteur his due in his struggle by extending his germ theory to all infections and contagious diseases, becoming his most famous advocate.

Pasteur's application of science to practical problems prompted the French government to demand him to lead a team to study the disease that had arisen in the silk industry in 1865. After three years of investigation, the disease was attributed to a parasite and they recommended ways to keep silkworms healthy, free from germs. Pasteur's success gave a more distinguished view of the theory that diseases are germ-borne. Tests have begun in medical research around the world. But during one of his works Pasteur had a stroke. While this did not affect the pace and ambition of his studies, his left side remained partially paralyzed for the rest of his life.

Pasteur's first study of microbial diseases was on anthrax, which not only was one of the main problems of the French livestock industry but also affecting humans. The bacterial cause was identified in 1876 by Robert Koch. Although Pasteur is best known for the vaccine he produced for this disease, he opposed some aspects of Koch's work. He followed the principle of vaccination against smallpox, that is, he predicted that mild disease can revert to virulent strain. He exposed the anthrax bacteria to the air and its virulence decreased. The laboratory results were successful. So he undertook a field trial at Pouilly-le-Fort near Paris in 1881.

Twenty-five sheep were vaccinated and an equal number of sheep were in the control group. Two weeks later, all of them made infected by anthrax. Nearly all of the vaccinated sheep survived, while almost all those who were not vaccinated died. Pasteur's work had shown that in addition to directly benefiting French farmers, vaccination could be applied to many, even all infectious diseases. He was welcomed as a celebrity in the International Medical Congress in 1881 and received great support from the French state.

Louis Pasteur and the rabies vaccine

Pasteur's humanistic stance and popularity led to the many reproductions of his images in the media, including chocolate boxes.
Pasteur's humanistic stance and popularity led to the many reproductions of his images in the media, including chocolate boxes.

But even bigger improvements were imminent. His next project was a protective vaccine against rabies. Its unpredictability and the fact that the symptoms, once appeared, bring a terrible death that could not be prevented were causing great concern in the public. Pasteur and his increasing number of assistants first reproduced the disease in laboratory dogs and rabbits under controlled conditions. The first trials in dogs were successful. Then, they switched to trials on humans due to the public pressure and also the increased reliance on the new vaccine.

However, the rabies vaccine was not used for protection, but to treat people who were already infected. The aim was to strengthen immunity by taking advantage of the long incubation period. The first human subject was a boy named Joseph Meister who was bitten by a rabid dog in eastern France. It was brought by her parents, who knew of Pasteur's possible life-saving treatment. The boy survived with treatment. After this case, the vaccine was tried on another child, the result was again positive. Once it was made public in October 1885, rabid dog bitten victims from France and Europe and soon all over the world flocked to Paris to receive this free treatment.

The press published Pasteur's newly popular rabies treatment on their front pages. They celebrated Pasteur as the great scientist and humanist who promised to rid humanity of infectious diseases. He received many new awards, but most importantly, there were donations from the public that allow him to set up an institute to develop further vaccines and other life-saving innovations. With donations from around the world, the Pasteur Institute officially opened in November 1888.

This great man's health had deteriorated. Although he was still in the laboratory and the clinic, he could not take an active role in any research. When he died in 1895, he was proposed to be buried in the Pantheon alongside other French heroes with a large public funeral. But Pasteur and his family had already made their plans. A scientist who redefined the place of laboratory research in science and public relations was buried in the crypt in his institute, the most appropriate place.