Prof. William Reveille, The Irish Times
Thu Jun 17 2004

Ask any French person to name the 10 most important of their compatriots ever and it is a sure bet that Louis Pasteur will figure prominently on the list.

Pasteur led an amazingly productive scientific life, making pioneering discoveries in medicine and chemistry and applying his science to solve problems of major economic importance to France and to revolutionise medical concepts of disease and its prevention. France is rightly proud of Pasteur. I will summarise Pasteur’s scientific work in a two-part article, the second part to appear next week.

Louis Pasteur was born in 1822 in Dole, in eastern France about 400 kilometres south east of Paris, the only son of a poorly educated tanner, Jean Pasteur. In his early years at school, Louis showed little interest in academic subjects, but when science came up on the curriculum he began to show great application. Encouraged by his father, Pasteur entered the École Normale Supérieure in Paris in 1837, a prestigious university devoted to training outstanding students for university careers.

Louis received an MSc in 1845 and then began work on his PhD in chemistry, a study of crystals, then an emerging branch of chemistry. He studied tartaric acid crystals, found in sediments of fermenting wine. Crystals of para-tartaric acid are also found in the sediments. The chemical composition of these two acids had already been found to be identical. Experts had also declared that their crystals were identical.

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But a mystery remained. When dissolved in water, tartaric acid rotated a beam of polarised light passing through it to the right, whereas para-tartaric acid did not rotate the light. Pasteur became convinced that the internal structure of the two acids must be different and, despite the experts, he believed this difference would show itself in the crystal form.

Pasteur found that all crystals of tartaric acid looked identical under the microscope, whereas crystals of para-tartaric acid could be divided into two very similar but not quite identical types, each a mirror image of the other – just as your left hand is a mirror image of your right hand.

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Pasteur separated the two types of para-tartaric acid crystal into two heaps. He dissolved each heap separately in water and found that one type rotated polarised light to the left and the other rotated it to the right. It was now clear that organic molecules with the same chemical composition can take up unique and different shapes in space. Pasteur’s observations began the new science of stereo chemistry.

These findings had a deeper meaning for Pasteur. He believed that asymmetric molecules such as he had discovered were characteristically produced by living processes. This far-sighted prediction proved correct. For example, proteins – pre-eminently important large biomolecules found in all cells – are made from small molecules called amino acids. Amino acids can occur in left-handed and right-handed forms but living organisms exclusively use only the left-handed forms.

In 1854 Pasteur was appointed professor of chemistry at the Faculty of Science in Lille, France. In 1856 he was approached by a local distillery having problems manufacturing alcohol by fermenting beetroot. The fermentation was erratic, often yielding lactic acid rather than alcohol.

Pasteur sorted out the whole problem in a few years of brilliant investigation, at the same time starting the new science of microbiology. He found that when fermentations went well, budding yeast cells were unaccompanied by other microbes. But when the fermentation produced lactic acid instead of alcohol, small rod-shaped microbes accompanied the yeast cells. He also found that fermentation produced complex organic compounds in addition to alcohol and that some of these compounds rotated polarised light.

As we know, he suspected that only living cells produced such asymmetrical molecules. He concluded and proved that living yeast cells were responsible for forming alcohol from sugar and that souring of fermentations was caused by contaminating micro-organisms.

Pasteur returned to the École Normale Supérieure in Paris in 1857 as director of scientific studies. He now turned his attention to the doctrine of spontaneous generation. The ancient Greeks believed that small animals such as worms and rodents spontaneously sprang to life from non-living matter such as rotting food. The Italian, Francesco Redi, disproved the idea of maggots spontaneously arising from meat in 1668. No maggots appeared in meat when he prevented flies from laying eggs on it. However, scientists still clung persistently to the notion of the spontaneous generation of microscopic animals.

Pasteur finally disproved this idea. He boiled broth in order to kill the microbes in it. He now allowed air to circulate over the broth, but, using ingenious devices, prevented microbes in the air from contacting the broth. No microbes arose in this broth. However, microbes flourished vigorously in the broth when they were allowed in with the air and made contact with the broth.

Pasteur had shown that life comes only from life.

William Reville is associate professor of biochemistry and director of microscopy at University College Cork

Source: The Irish Timeshttps://www.irishtimes.com/news/pasteur-proves-life-only-comes-from-life-1.1145281

Louis Pasteur – his research saved the lives of millions

Published by  Mirja Holtrop at  December 19, 2016

Louis Pasteur (1822-95) was a French chemist who taught at Strasbourg, Lille, and Paris. He discovered that the real causes of epidemics were bacteria and other microorganisms. However, like many visionary ideas that are born ahead of their time, acceptance didn’t come easily.

During his early years of research, the French silkworm industry had asked Pasteur for help in finding out the causes of an epidemic that was killing their worm colonies, and whether there was a possible cure. His eventual discovery – that microorganisms were causing the colony deaths – saved the French silk industry from bankruptcy. This gave him the first hint that he was on the right path. He then spent the rest of his life researching germs and developing vaccines against them.

He presented his findings to fellow researchers from the French Academy of Sciences. At first, however, they didn’t take him seriously.

Some scientists, such as Robert Koch, categorized microorganisms as phenomena of nature that temporarily appeared and then disappeared but were not actually alive.

This criticism didn’t sit well with Pasteur. “I give them experiments and they respond with speeches!”, he once said. In his mind, the fixed ideas and inflexible thinking patterns at that time were dangerous both for millions of lives and the future of medicine. He saw the need for a ‘living flame of research’ to bring light into the darkness.

So Pasteur persisted with his work and became even more determined. He had a wife, and five children – of which sadly only two survived – and he hardly saw them. He dedicated every minute of his waking days to research, as he felt he could save many more children’s lives if he was right. His numerous experiments proved that microorganisms do not make sudden, temporary appearances but that they emerge when in contact with oxygen. He isolated microorganisms, named and categorized them, and found in them the causes for many diseases of animals and humans.

After he eventually published his findings, suddenly veterinarians and doctors became his opponents. They could not get used to the fact that a chemist and microbiologist now had a say on the matter of diseases, a subject which had – until then – been entirely their own field.

But Pasteur never gave up. He went into hospitals and taught doctors to sterilize their surgical instruments. They could see the results quickly – less people got infections – and so became more and more convinced that Pasteur was right.

A new path for research was created: medical microbiology and bacteriology.

Microorganisms under a microscope.

Pasteur carried on working in hospitals, developed vaccines, and became successful. When he saved a 9-year-old boy who had been bitten by a rabies-infected animal, he, his life, and his research finally became legendary. As news of his work spread, he became famous all over Europe.

But it was not only humans that he helped. Anthrax was a common disease in sheep, and his vaccine prevented many farmers from financial loss.

Pasteur, by now a national celebrity in France, published his own scientific newspaper and opened the famous ‘Pasteur Institute’. He managed this institute right up until his death in 1895. In his last speech to young researchers he reprimanded them to not simply measure their work by the credit they receive at the time, but to stay on track no matter what happens.

“In the last hour of one’s life, everyone has to say: I have done all that I could.”

Pasteur’s life is an example of commitment and strength. Even when times were tough, he never gave up believing in what he was doing.

“Science is the torch that illuminates the world”

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