LOUIS PASTEUR (1822- 95)

1865 – France

‘Many human diseases have their origin in micro-organisms’

1862 – ‘Memoire sur les corpuscles organises qui existent dans l’atmosphere’ (Note on Organized Corpuscles that exist in the Atmosphere) – Puts an end to centuries of debate on the theory of spontaneous generation.

Although a chemist, Pasteur is best remembered for his contributions to medicine. His name is used to describe the process of ‘pasteurisation’.
Pasteur proved that living microorganisms cause fermentation. Previously scientists had assumed that fermentation was a chemical process.
Pasteur showed that the alcohol in fermentation was made by the yeast microbe. He also realised that when fermentation went wrong it was due to other germs.

In 1863 he showed that brief, moderate heating of wine and beer kills germs, thereby sterilizing the foodstuffs and ending the fermentation process. The process now known as pasteurisation is still used in the food industry.

His investigations led him to believe that microorganisms could also cause disease in humans. Pasteur realized the dangers of infection, but the English surgeon JOSEPH LISTER (1827-1912) is credited with developing and systematizing the notion of antiseptic surgery so that operations could be made safer if an ‘antiseptic’ procedure was introduced to destroy microbes and curb the infections that followed wounds or surgery.

In 1876, Pasteur confirmed the findings of ROBERT KOCH’s discovery of the anthrax bacillus. After EDWARD JENNER’s breakthrough in the development of vaccination against smallpox, little had been done to take advantage of the potential of this treatment against other disease.

In 1882 Pasteur successfully applied his discovery of vaccination by attenuated culture of microorganisms to anthrax and in 1885 to the treatment of rabies in humans.

On 14 November 1888 the Pasteur Institute opened in Paris.

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ROBERT KOCH (1843-1910)

1876 – Germany

‘Koch’s postulates – four conditions that need to be satisfied to be sure that a particular type of bacteria causes disease’

Koch developed methods of staining bacteria that enabled him not only to see them under a microscope, but also to differentiate between the various strains of microorganisms that he found.

Koch proved that specific organisms cause specific diseases and in addition, that pollution could spread disease.
He developed methods for obtaining pure cultures of bacteria and laid down Koch’s Postulates.

photo portrait of ROBERT KOCH who devised 'KOCH's POSTULATES' ©


His colleague RICHARD JULIUS PETRI (1852-1921) designed a shallow flat dish that allowed him to grow microorganisms on a solid flat surface, and thus easily separate colonies of bacteria. Until then scientists had grown bacteria in flasks, or injected them into animals.

Koch’s rules for identifying harmful bacteria

  • – the micro-organism must be identified and seen in all animals that suffer the same disease
  • – it must be cultured through several generations
  • – these later generations of bacteria must be capable of causing the disease
  • – the same agent must be found in a newly infected animal as was found in the original victim


Using this set of criteria he identified the organisms responsible for more than twenty diseases, including tuberculosis, salmonella, cholera, pneumonia and meningitis.

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