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Sunday, December 4, 2011

Pasteur to Penicillin

When I was visiting a science museum in Paris in 1949, I remember being thrilled to come across the very swan neck flask that Pasteur had used in his famous experiment in 1862. He did that experiment to prove that the popular belief in ‘spontaneous generation’ - that life just starting up of its own accord - was not the reason why any food left open to the air ‘went bad’ or began to ferment.

The results of that experiment would be far reaching. One of the main reasons that science has been so successful is that experimental outcomes are openly reported and thus able to be used by other scientists with confidence as the basis for their own work. This post is about a chain of important discoveries affecting all mankind that started with the work done in the 1670’s by Leeuwenhoek, the Dutch scientist famous for making microscopes. He had reported that through them he could see a multitude of very tiny microscopic life forms. This knowledge subsequently convinced Pasteur that there were all sorts of microorganisms, mostly bacteria, viruses and fungi spores that you couldn’t see suspended in the air and that they were drifting down onto food and infected it.

To prove his point, Pasteur did a simple but very famous experiment. He put some nourishing broth in 2 identical long stemmed flasks boiled them both to kill any microorganisms they contained and one he left the top open while with the other, he melted the glass at the top of the stem and pulled it into a long swan neck shaped tube as shown in the picture. It was still open to the air but microorganisms could not fall into the broth and, as Pasteur predicted, it did not spoil as the other one did.

Influenced by Pasteur’s results and writings, Joseph Lister, a surgeon in Scotland, became convinced that the reason open wounds usually became infected was because the harmful microbial life forms from the air were similarly contaminating them. By 1869, he was sterilizing his instruments, cleaning open wounds and covering them with bandages covered with an antiseptic. His results were so dramatic with so many lives saved that he spread the word and medical science was revolutionized through reading about his methods and following his example.

The story of Alexander Fleming who discovered penicillin can also be connected to Pasteur’s work. Although it had been suspected for many years that disease could be passed from one person to another by being in close proximity, Pasteur proved that bacteria suspended in air could cause disease. In 1928, Fleming was looking for a substance that would not be harmful to the body but could kill the disease-causing germs a person had breathed in. He was growing a type of Staphylococcus bacteria in covered glass dishes and trying to kill them with different substances. By chance while cleaning up some discarded dishes, he happened on one that had been open to the air and a mold was growing in it. Observant, he noticed that the mold was killing the ‘staph’ germs all around it. Recognizing his ‘find’ as important, he had a colleague identify the mold as a Penicillium type and he called its active ingredient penicillin. His chance discovery opened up the whole field of antibiotics.

When you prepare food be aware, like Pasteur, that you are creating conditions for air born contamination. Cover and refrigerate. Rie


  1. Hi Rie, I enjoy reading your blog, very informative and oddly enough several recently have been on subjects of more than casual interest to me. Pat NC(USA)

  2. Thank you Pat for your comment - i rarely get feedback and I am delighted my eclectic fare is sometimes of interest. Rie