Louis Pasteur: Father of Microbiology

Louis Pasteur, a microbiologist and chemist known for discovering the rabies vaccine, was born in Dole, France, in 1822. Both his parents dreamed of making their only son a scientist, but Louis was not in a position to meet these expectations. Young Louis was a diligent student at school, but he was a bit shy. Louis had only one interest in drawing, which eventually turned into a passion. Especially his talent in portraiture… Everyone predicted that Louis would have a future as an artist, and his sisters were proud of his drawings and portraits. His father, who wanted to see him as a teacher or perhaps a college principal one day, was discouraged by Louis’s lack of interest in science.

A Genius is Rising!

Suddenly, Louis’s interest turned to reading! His passion for art had diminished, and his desire to read all kinds of books had taken its place. He had no interest in anything else and spent his energy and strength only on reading. This desire would lead Louis to the path of science in the future. This enthusiasm for reading and learning made Louis extremely curious and eager to learn. Over time, his unexpected success in lessons surprised everyone and made his father especially very proud. In lessons, Louis, who did not find the information in the book satisfactory, would drive his teachers crazy with his questions. Louis was interested in philosophy and science, especially chemistry… He was determined; he would continue his education in science.

He began his higher education at the École Normale, a highly distinguished school in Paris. Here he began taking lessons from Antoine Jerome Balard, one of the most famous chemists of his time, who was famous for discovering the element bromine. Pasteur desired to be closer to science and was burning with the desire to produce science. He soon began working as a volunteer in the laboratory of Jean-Baptiste Dumas, one of the founders of organic chemistry and known for his pioneering work in organic synthesis. During these early university years, he spent all of his time in the library after his classes and laboratory work, and he attracted attention with his determination and curiosity.

Questions About the Article! 

“Pasteur! Despite all his talents, he never does anything ordinary. He always tries to solve unsolvable problems!”

Em. Verde

During this period, Pasteur was also incredibly interested in mineralogy, but mineralogy alone did not interest Pasteur. The question he was most curious about was the relationship between the internal structure of matter and its external crystalline form. Why did different objects have different crystal structures? Could the basic structure of the matter inside an object be predicted by looking at its shape? These questions were very abstract at the time and absurd in the eyes of those who defended only useful knowledge for society. The subject that interested Pasteur seemed so obscure and incomprehensible at the time that most scientists stayed away from these questions. According to Pasteur, courage was required in everything, just like science, to achieve real success. The internal structure of matter, which caused the external appearances of different objects, occupied Pasteur’s mind for a long time.

When he graduated from the École Normale with the highest grades, he had only one thought: to do research in a laboratory. This time, he was lucky. He didn’t work in just any laboratory, but instead worked with Professor Balard, the discoverer of the element bromine, which he had never dared to imagine.

Molecular Asymmetry!

“There’s a young man around here named Pasteur. He has some great ideas. He enlightens everything he touches.”  

Biot

Recently, it was understood by Jean-Baptiste Biot that some objects can change their polarization plane. This could be related to the crystalline structure of the object and shed light on the molecular structure of the substance. According to Pasteur, if the solutions of two objects consisting of the same particles react differently to light, this could only be because the particles are grouped differently. The deviation of the polarization plane was the shifting of the light that was polarized and positioned in a single plane from the plane after interaction with the matter.

This should indicate an asymmetry in the atomic grouping in the substance, and if this assumption is correct, then two objects that react differently to light cannot have the same shape. If the polarization plane of one solution deviates and the other does not, the same crystals cannot be formed from those solutions. Grape acid and tartaric acid react differently to polarized light, but their chemical content is the same. He decided that the crystals of grape acid, whose polarization plane does not rotate, were symmetrical, and took two samples of tartaric acid with identical contents from grape acid. The polarization plane of one acid rotated to the right, and the polarization plane of the other rotated to the left! Pasteur divided these acids, whose new properties he discovered, into “right” and “left” acids.

Pasteur’s work was later continued by J.H. van’t Hoff and J.A. LeBel, and a new branch of chemistry called stereochemistry, which “studies the spatial arrangement of atoms and molecules”, was found. This branch of science allowed us to delve deeper into the mysteries of the structure of matter.

Pasteur developed his doctrine of “molecular asymmetry”, which examines the relationship between the bonding patterns of atoms and their optical properties and crystal structure, with more than twenty studies between 1848 and 1854. During these studies, he earned the title of professor in Strasbourg. Here he married Marie Laurent, the daughter of the Rector of the Strasbourg Academy.

The Germ Theory of Fermentation!

”A new science was born, one that led to a real revolution in our knowledge of deadly and infectious diseases.”

Pasteur

He focused on molecular asymmetry for a while, but gave up on advancing in this field. He changed direction to move towards a new field of science. He moved beyond theoretical subjects and focused on more practical areas; although it seemed that he was focused on everyday and simple subjects such as beer, wine, vinegar, this was not the case. He observed that mold fungus affected fermentation in a solution containing “right” and “left” acids, breaking down one acid and not harming the other. This observation inspired him to think that interesting discoveries could be made in the fermentation process.

In 1853, he was appointed dean of the University of Lille, famous for its vinegar and alcohol production. He abandoned all his previous studies to study a single subject, lactic acid fermentation, and turned to a new field.

How Do Decay and Deterioration Happen?

The chaotic events in all the transformations and changes in the living world we see around us can be explained with two concepts: life and death. Living things maintain their chemical and biological systems throughout their lives, then succumb to the laws of thermodynamics and die. Here comes to mind a question that Pasteur also asked. How do the decay and deterioration events that death will bring occur? His scientific studies brought the answer to the question for humanity. Pasteur showed that there is a third world: the world of beings that stand on the border of life and death, acting as mediators between living and inanimate nature…

Until then, it was known that fermentation was the transformation of organic substances, such as sugar, into simpler components such as alcohol and carbon dioxide, under the influence of fermentation, and this process was considered to be only chemical, and it was thought that decay and deterioration occurred through the direct effect of oxygen in the air on organic matter. Pasteur realized in his early studies that fermentation was not chemical, that it occurred due to living beings, and that it was a biological process. He began his work on lactic acid fermentation. Lactic acid fermentation is the transformation of sugar into lactic acid, and for example, this process occurs when milk sours. Since the sugar in the milk turns into acid, the casein in the milk is finished.

During lactic acid fermentation, a cloudy, gray precipitate forms. Pasteur suspected that this substance, thought to be a byproduct of fermentation, was the source of the whole process, and he took it and put it in other solutions containing organic chemicals, and fermentation occurred each time. This gray substance was lactic fermentation bacteria. Pasteur had carried out the first isolation and reproduction experiments of microbes, and had taken the first steps in bacteriological techniques. The results of Pasteur’s experiments were that microorganisms caused the fermentation process; that each fermentation, putrefaction, and decomposition process included many different types; and that many different specific microorganisms played a role in all of them.

While developing the theory of fermentation, Pasteur conducted numerous different experiments and was targeted by the supporters of the old theory for a long time. However, he crushed his opponents under the greatness of his scientific revolution without leaving any arguments or questions unanswered. The supporters of the old theory still claimed that oxygen was the main element that played a role in fermentation. Pasteur showed that oxygen had a negative effect on fermentation processes, such as wine fermentation without oxygen, and that anaerobic bacteria (bacteria that can grow in an oxygen-free environment and are poisoned by oxygen) played a role in this process.

The Collapse of Spontaneous Generation: Pasteur’s Experiment

“Let me tell you the secret that led me to my goal. My sole strength is in my tenacity.

Pasteur

 

In 1857, he returned from the University of Lille to the École Normale in Paris and rolled up his sleeves for his new studies. However, Pasteur encountered great economic difficulties on the path he set out to carry out his research. The Ministry of National Education did not see Pasteur’s work as an investment value, but Pasteur, whose research would earn France billions in the future, set up a laboratory and began his work despite all the difficulties.

He worked on the problem of “spontaneous generation” by including previous fermentation studies. “Spontaneous generation” or “spontaneous generation” in living things was the spontaneous emergence of microbes in inanimate organic mixtures such as broth, which was accepted at the time, and was a thousand-year-old problem. Pasteur designed an ingenious experimental setup to disprove the theory of spontaneous generation. He put broth in two containers and attached swan-necked pipes that allowed air in but prevented dust from entering. First, he sterilized both containers. Then he broke the neck of one container and left the other untouched. Bacteria were observed to grow in the broken container, while no living thing formed in the untouched one. This experiment proved that living things did not come spontaneously, but from previous living things. In this way, the idea that “every living thing comes from a living thing before it” was confirmed.

Fighting More Germs!

“Opportunities are for the well-focused mind to seize.”

Pasteur

It was necessary to prove not only the breakdown of sugars in food, but also that all decomposition and decay were caused by living beings and that these reactions could not have occurred without microbes. In the early 60s, he was visiting hospitals and pondering gangrene, inflammation, and infections. These ideas would fundamentally change the world of medicine in the future, and even at that time, Pasteur had not the slightest doubt about this.

However, his work was interrupted by an epidemic that emerged in silkworms. The disease that emerged in silkworms had brought the entire silk industry to a standstill. Silk could not be produced in most of Europe and Asia, and an economic crisis was experienced. In order to find a solution to this issue, Pasteur studied the ways in which the infectious microbes that caused this disease spread through various experiments and found how the source could be destroyed.

This success brought Pasteur great prestige, but he lost his health during his intensive work. According to the doctors, there was a high probability of paralysis, and when they told him that his intensive work caused the disease, Pasteur’s thoughts on this issue were clear: “My work threatens my health… My health is there for me to wear it out with work anyway.” After struggling with this difficult disease for a few years, he was assigned a large laboratory.

Revolution in Medicine!

One of the most important branches of medicine changed under the influence of Pasteur’s ideas. Hospitals were facing terrible deaths due to wound infections that had become hotbeds of microbes. In 1865, Joseph Lister proposed the “antiseptic method” for wound treatment and surgical interventions. Lister’s method was widely accepted within ten years. While conveying his findings to Pasteur, Lister wrote: “…your brilliant studies on putrefaction inspired my work on the antiseptic method.” The essence of this method was to prevent the microbes that caused putrefaction from reaching the deep tissues of the human body. After the wounds were cleaned with diluted carbolic acid, iodoform or other antiseptic substances were applied, and then they were dressed with cotton soaked in carbolic acid. Many pieces of evidence were in Lister’s favor. Lister sterilized the bandages by eliminating microbes and preventing contamination. Therefore, it was concluded that microbes were the source of infection.

Humanity’s Biggest Victory Against Diseases!

“The most tremendous revolution that changed the foundations of medical science that has existed for three thousand years was made by a person who was a stranger to the world of medicine, Pasteur.”

Paul Brouardel

Anthrax was a devastating disease that lasted for a long time all over the world. During the peak of the disease, thousands of sheep and cattle died, especially in the agricultural sector, and this caused great harm to the farmers. People were dying in terrible pain after contracting the infection from animals. Medical experiments were conducted for years, but no definitive decision was reached as to whether the source of the disease was microbes.

Pasteur began his experiments on the subject. He placed a drop of blood taken from a sick animal into a liquid containing nutrients. The organisms in the blood multiplied in this environment. He transferred one drop of this culture into a new tube, then into the next, and the next. Thus, a pure microbe culture without traces of the first blood was obtained. Pasteur inoculated this culture into animals and observed that they contracted anthrax. It was clearly seen that this culture had nothing to do with blood. Anthrax was caused only and only by bacteria. The relationship between microbes and the epidemic was proven for the first time thanks to flawless experiments.

But the bigger problem was finding a solution to the disease. A method had to be developed to neutralize the microbes. This was the most complicated and obscure of the subjects Pasteur had ever worked on. In addition to his research on anthrax, he had added another disease known as “chicken cholera.” This disease was killing chickens and other poultry. Pasteur obtained a pure culture of the microbe that caused this disease and began to study the culture under different conditions. A fresh culture inoculated into chickens usually killed them. However, a culture that had been kept in a test tube for three months was infectious but not fatal. The chickens got sick but recovered after a while. It had long been known that people and animals that had contracted measles and smallpox and recovered from these diseases were resistant to the disease, at least for a while. Could chickens inoculated with a weakened disease culture also become immune? Pasteur tested this by inoculating them with a fresh disease culture, a powerful poison. The chickens showed resistance to the disease! The weakened microbe provided preliminary protection against the disease!

Veterinarians and ranchers who received weakened samples of the chicken cholera microbe from Pasteur saw that the culture did indeed protect chickens from the disease. Pasteur’s experiments were presented to the Academy of Sciences. Large-scale experiments were carried out, and Pasteur’s experiments were proven before a large academic audience!

Medicine could now cure diseases! The goal that medicine had sought for thousands of years had finally been achieved. The causes of epidemics had been discovered, and methods of combating them had been developed. Even if Pasteur had only found the cause of disease, this discovery would have been a significant turning point in medicine. But he did more; he discovered the microbes that caused the disease, showed how to isolate and culture the microbes, and defeated the disease by producing a vaccine for the microbes. Thanks to Pasteur’s methods, medicine had done more in thirty years than it had done in the last three thousand years.

Rabies Vaccine! 

In the short period between 1857 and the early 1880s, important developments took place and many new ideas began to be implemented. In the 80s, Pasteur’s ideas became known to everyone. Bacteriology departments began to be established in medical schools, and agricultural experts began to work on microbes in the soil. All of Pasteur’s theoretical and experimental studies created a revolution in daily life.

Pasteur then wanted to move on to the more difficult side of human diseases, where ethical concerns were more pressing. He looked for a disease that affected both animals and humans, so that most of his experiments could be done on animals. From 1880 onwards, he focused on rabies research and transformed his laboratory on Ulm Street into a zoo. Animals were everywhere in cages, many of them in pain. These animals were victims to be experimented on for the sake of science. Pasteur had to use these animals as test subjects to avoid leaving humans in the clutches of cruel diseases.

Pasteur had great difficulties when he started to study rabies. First of all, the microbe that caused the disease could not be identified, so it was impossible to isolate it. However, Pasteur considered the possibility of turning rabies poison into an antidote. After a series of experiments, Pasteur discovered that rabies poison was concentrated throughout the nervous system, especially in the brain and spinal cord. This meant that he had discovered the real poison of rabies in the nerve cells of rabid animals. He then developed a method to weaken this poison. The poison was stored in a dry environment, and as it dried, the effect of the poison decreased. The resulting poison was harmless and not fatal. Experiments on animals had yielded positive results. Now new experiments had to be conducted on humans.

Nine-year-old Joseph Meister was attacked by a rabid dog on his way to school one day. After examining the wounds, the doctor referred the young boy to the only person who could treat him: Louis Pasteur. Meister’s mother came to Pasteur’s laboratory with her son. For a while, young Meister received regular vaccinations in Pasteur’s laboratory and was discharged in good health three weeks later. Young Meister had not contracted rabies.

His Last Years

After this incident, patients and academics from all over the world who wanted to learn more about this field of science flocked to Pasteur’s laboratory. As a result of these developments, Pasteur decided to establish an institute and this scientific center was established within 2 years. Among those who supported the establishment of the institute was the Ottoman Sultan Abdulhamid II. Ten thousand francs of aid came from the Ottomans and many Turkish doctors were sent to the institute.

Pasteur, who was the head of the institute for a few years, had a very advanced disease and was forced to spend the last years of his life inactive. His friends always heard the same complaint from Pasteur: “I can’t work anymore!” This scientist, who made it possible to cure many diseases, succumbed to paralysis in 1895, leaving his science and discoveries as a legacy to humanity.

Today, the worker in the workshop, the scientist in the laboratory, the farmer in the field, the doctor at his patient’s bedside, the veterinarian at his pet, the wine and beer makers…all of these are governed by Pasteur’s ideas.

References and Further Reading

Engelhardt MA (2019) Pasteur, the Chemist Who Revolutionized Medicine. Trc. Alyona Kelleci. Ankara: Etkin Publishing House.

Zamosky, L. (2008). Louis Pasteur: Founder of Microbiology. United States of America: Capstone.

Pasteur, L. (1996). Germ theory and its applications to medicine & the antiseptic principle of the practice of surgery. United States of America, Prometheus Books.