Louis Jean Pasteur

Louis Jean Pasteur

Louis Pasteur (/ˈluːi pæˈstɜːr/, French: [lwi pastœʁ]; December 27, 1822 – September 28, 1895) was a French biologist, microbiologist and chemist renowned for his discoveries of the principles of vaccination, microbial fermentation and pasteurization. He is remembered for his remarkable breakthroughs in the causes and prevention of diseases, and his discoveries have saved many lives ever since. He reduced mortality from puerperal fever, and created the first vaccines for rabies and anthrax.

His medical discoveries provided direct support for the germ theory of disease and its application in clinical medicine. He is best known to the general public for his invention of the technique of treating milk and wine to stop bacterial contamination, a process now called pasteurization. He is regarded as one of the three main founders of bacteriology, together with Ferdinand Cohn and Robert Koch, and is popularly known as the “father of microbiology”.

Pasteur was responsible for disproving the doctrine of spontaneous generation. He performed experiments that showed that without contamination, microorganisms could not develop. Under the auspices of the French Academy of Sciences, he demonstrated that in sterilized and sealed flasks nothing ever developed, and in sterilized but open flasks microorganisms could grow.Although Pasteur was not the first to propose the germ theory, his experiments indicated its correctness and convinced most of Europe that it was true.

Today, he is often regarded as one of the fathers of germ theory.Pasteur made significant discoveries in chemistry, most notably on the molecular basis for the asymmetry of certain crystals and racemization. Early in his career, his investigation of tartaric acid resulted in the first resolution of what is now called optical isomers. His work led the way to the current understanding of a fundamental principle in the structure of organic compounds.

He was the director of the Pasteur Institute, established in 1887, until his death, and his body was interred in a vault beneath the institute. Although Pasteur made groundbreaking experiments, his reputation became associated with various controversies. Historical reassessment of his notebook revealed that he practiced deception to overcome his rivals.

Early life
Louis Pasteur was born on December 27, 1822, in Dole, Jura, France, to a Catholic family of a poor tanner. He was the third child of Jean-Joseph Pasteur and Jeanne-Etiennette Roqui. The family moved to Marnoz in 1826 and then to Arbois in 1827. Pasteur entered primary school in 1831.

He was an average student in his early years, and not particularly academic, as his interests were fishing and sketching. He drew many pastels and portraits of his parents, friends and neighbors. Pasteur attended secondary school at the Collège d’Arbois. In October 1838, he left for Paris to join the Pension Barbet, but became homesick and returned in November.

In 1839, he entered the Collège Royal at Besançon to study philosophy and earned his Bachelor of Letters degree in 1840.He was appointed a tutor at the Besançon college while continuing a degree science course with special mathematics. He failed his first examination in 1841. He managed to pass the baccalauréat scientifique (general science) degree in 1842 from Dijon but with a mediocre grade in chemistry.

Later in 1842, Pasteur took the entrance test for the École Normale Supérieure. He passed the first set of tests, but because his ranking was low, Pasteur decided not to continue and try again next year. He went back to the Pension Barbet to prepare for the test. He also attended classes at the Lycée Saint-Louis and lectures of Jean-Baptiste Dumas at the Sorbonne. In 1843, he passed the test with a high ranking and entered the École Normale Supérieure. In 1845 he received the licencié ès sciences (Master of Science) degree. In 1846, he was appointed professor of physics at the Collège de Tournon (now called Lycée Gabriel-Faure [fr]) in Ardèche, but the chemist Antoine Jérôme Balard wanted him back at the École Normale Supérieure as a graduate laboratory assistant (agrégé préparateur). He joined Balard and simultaneously started his research in crystallography and in 1847, he submitted his two theses, one in chemistry and the other in physics.

After serving briefly as professor of physics at the Dijon Lycée in 1848, he became professor of chemistry at the University of Strasbourg, where he met and courted Marie Laurent, daughter of the university’s rector in 1849. They were married on May 29, 1849, and together had five children, only two of whom survived to adulthood; the other three died of typhoid.

Fermentation and germ theory of diseases
Pasteur was motivated to investigate fermentation while working at Lille. In 1856 a local wine manufacturer, M. Bigot, whose son was one of Pasteur’s students, sought for his advice on the problems of making beetroot alcohol and souring.

According to his son-in-law, René Vallery-Radot, in August 1857 Pasteur sent a paper about lactic acid fermentation to the Société des Sciences de Lille, but the paper was read three months later.A memoire was subsequently published on November 30, 1857. In the memoir, he developed his ideas stating that: “I intend to establish that, just as there is an alcoholic ferment, the yeast of beer, which is found everywhere that sugar is decomposed into alcohol and carbonic acid, so also there is a particular ferment, a lactic yeast, always present when sugar becomes lactic acid.”

Pasteur also wrote about alcoholic fermentation.It was published in full form in 1858.Jöns 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.He also demonstrated that, when a different microorganism contaminated the wine, lactic acid was produced, making the wine sour.In 1861, Pasteur observed that less sugar fermented per part of yeast when the yeast was exposed to air.The lower rate of fermentation aerobically became known as the Pasteur effect.

Immunology and vaccination
Chicken cholera
Pasteur’s later work on diseases included work on chicken cholera. He received cultures from Jean Joseph Henri Toussaint, and cultivated them in chicken broth. During this work, a culture of the responsible bacteria had spoiled and failed to induce the disease in some chickens he was infecting with the disease. Upon reusing these healthy chickens, Pasteur discovered he could not infect them, even with fresh bacteria; the weakened bacteria had caused the chickens to become immune to the disease, though they had caused only mild symptoms.

In 1879, his assistant, Charles Chamberland (of French origin), had been instructed to inoculate the chickens after Pasteur went on holiday. Chamberland failed to do this and went on holiday himself. On his return, the month-old cultures made the chickens unwell, but instead of the infections being fatal, as they usually were, the chickens recovered completely. Chamberland assumed an error had been made, and wanted to discard the apparently faulty culture, but Pasteur stopped him. He inoculated the chickens with virulent bacteria that killed other chickens, and they survived. Pasteur concluded that the animals were now immune to the disease.

In December 1879, Pasteur used a weakened culture of the bacteria to inoculate chickens. The chickens survived, and when he inoculated them with a virulent strain, they were immune to it. In 1880, Pasteur presented his results to the French Academy of Sciences, saying that the bacteria were weakened by contact with oxygen.

Anthrax
In the 1870s, he applied this immunization method to anthrax, which affected cattle, and aroused interest in combating other diseases. Pasteur cultivated bacteria from the blood of animals infected with anthrax. When he inoculated animals with the bacteria, anthrax occurred, proving that the bacteria was the cause of the disease.Many cattle were dying of anthrax in “cursed fields”. Pasteur was told that sheep that died from anthrax were buried in the field. Pasteur thought that earthworms might have brought the bacteria to the surface. He found anthrax bacteria in earthworms’ excrement, showing that he was correct. He told the farmers not to bury dead animals in the fields.

In 1880, Pasteur’s rival Jean-Joseph-Henri Toussaint, a veterinary surgeon, used carbolic acid to kill anthrax bacilli and tested the vaccine on sheep. Pasteur thought that this type of killed vaccine should not work because he believed that attenuated bacteria used up nutrients that the bacteria needed to grow. He thought oxidizing bacteria made them less virulent. In early 1881, Pasteur discovered that growing anthrax bacilli at about 42 °C made them unable to produce spores,and he described this method in a speech to the French Academy of Sciences on February 28.Later in 1881, veterinarian Hippolyte Rossignol proposed that the Société d’agriculture de Melun organize an experiment to test Pasteur’s vaccine. Pasteur agreed, and the experiment, conducted at Pouilly-le-Fort on sheep, goats and cows, was successful. Pasteur did not directly disclose how he prepared the vaccines used at Pouilly-le-Fort. His laboratory notebooks, now in the Bibliothèque Nationale in Paris, show that he actually used heat and potassium dichromate, similar to Toussaint’s method.

The notion of a weak form of a disease causing immunity to the virulent version was not new; this had been known for a long time for smallpox. Inoculation with smallpox (variolation) was known to result in a much less severe disease, and greatly reduced mortality, in comparison with the naturally acquired disease. Edward Jenner had also studied vaccination using cowpox (vaccinia) to give cross-immunity to smallpox in the late 1790s, and by the early 1800s vaccination had spread to most of Europe.

The difference between smallpox vaccination and anthrax or chicken cholera vaccination was that the latter two disease organisms had been artificially weakened, so a naturally weak form of the disease organism did not need to be found.This discovery revolutionized work in infectious diseases, and Pasteur gave these artificially weakened diseases the generic name of “vaccines”, in honour of Jenner’s discovery.

 

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Awards and honours
Pasteur was awarded 1,500 francs in 1853 by the Pharmaceutical Society for the synthesis of racemic acid. In 1856 the Royal Society of London presented him the Rumford Medal for his discovery of the nature of racemic acid and its relations to polarized light,and the Copley Medal in 1874 for his work on fermentation. He was elected a Foreign Member of the Royal Society (ForMemRS) in 1869.

The French Academy of Sciences awarded Pasteur the 1859 Montyon Prize for experimental physiology in 1860,and the Jecker Prize in 1861 and the Alhumbert Prize in 1862 for his experimental refutation of spontaneous generation.Though he lost elections in 1857 and 1861 for membership to the French Academy of Sciences, he won the 1862 election for membership to the mineralogy section.He was elected to permanent secretary of the physical science section of the academy in 1887 and held the position until 1889.

In 1873 Pasteur was elected to the Académie Nationale de Médecine and was made the commander in the Brazilian Order of the Rose.In 1881 he was elected to a seat at the Académie française left vacant by Émile Littré.Pasteur received the Albert Medal from the Royal Society of Arts in 1882.In 1883 he became foreign member of the Royal Netherlands Academy of Arts and Sciences.On June 8, 1886, the Ottoman Sultan Abdul Hamid II awarded Pasteur with the Order of the Medjidie (I Class) and 10000 Ottoman liras.Pasteur won the Leeuwenhoek Medal from the Royal Netherlands Academy of Arts and Sciences for his contributions to microbiology in 1895.
Pasteur was made a Chevalier of the Legion of Honour in 1853, promoted to Officer in 1863, to Commander in 1868, to Grand Officer in 1878 and made a Grand Cross of the Legion of Honor in 1881.

 

 

 

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