Robert Koch

Wikimedia Commons.

Robert Heinrich Herman Koch

Robert Koch was born in Germany on December 11, 1843. He was a pioneer in bacteriology and is known around the world for his method of determining the microbial cause of a disease, called Koch’s Postulates. Koch was an excellent student as a boy, teaching himself to read and write before even entering grade school. Koch went to the University of Göttingen to study natural science, yet soon after he switched to medicine. He graduated from medical school with highest honors, and started to work as a surgeon in the German province of Posen. Koch began his major research work during the Franco-Prussian War of 1870. Adjacent to his patient rooms, Koch had created a laboratory which he used to study an array of diseases and their causes. Subsequently, he bacme a medical professor in Berlin and had a much larger laboratory.  Koch and his students and co-workers developed a range of method for studying bacteria, many of which are still in use today.  For example, one of the laboratory technicians working for Koch, Angelina Fanny Hesse, came up with the method of isolating pure cultures using agar gel.  This method is still used today. Koch used this technique (among others) to discover the bacterial causes of anthrax, cholera, and tuberculosis. Koch’s work was highly respected and he was awarded the 1905 Nobel Prize in Medicine. Koch’s work established the germ theory of disease, which states that many diseases have bacterial causes. Koch died on May 27, 1910, in Baden-Baden.

M0013306 R. Koch, 12 slides of bacteria
Robert Koch, 12 slides of bacteria Credit: Wellcome Library, London.

Koch’s Postulates

Before Robert Koch was able to find and identity the causes of disease, he had to develop a system of isolating and identifying the pathogen. This method allows scientist to establish a direct causative effect between disease and microbe.

Koch’s Postulates are as follows:

  1. The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
  2. The microorganism must be isolated from a diseased organism and grown in pure culture.
  3. The cultured microorganism should cause disease when introduced into a healthy organism.
  4. The microorganism must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

Using this method, Koch could confirm that only people suffering from cholera, for example, would have the microbe responsible for cholera. Koch could then isolate this organism, and grow in it in agar gel, a clear medium that would show the specific microbe for cholera only. Then Koch used this method to introduce this isolated microbe into a healthy experimental animal, in order for it to get infected with the disease. Then the microbe would also be isolated from the experimental animal, if the microbes are a match then the disease would be confirmed. Using this specific method that Robert Koch invented, he was able to confirm the bacteria which caused the disease.

Discovery of Cholera

Cholera was a serious public health threat in the 19th century. In 1883, cholera broke out in Egypt and Europeans feared that the disease would spread to their countries.  Koch wanted to help address this concern and traveled with a group of scientists in order to find the microbe that caused cholera. They found a person who had died of cholera, but not of any other disease in order to use the first postulate to isolate the microbe that caused cholera. Yet, Koch was unable to isolate and purify the microbe in Egypt. Soon after, the epidemic died out and Koch was unable to continue his work. In 1883, Koch sailed to Calcutta, India, where cholera was widespread. This is where group continued their research work.  They were able to finally isolate a pure culture of the microbe that caused cholera.

Robert Koch (3rd from left) and his colleagues in Egypt in 1884. Wikimedia Commons.

On January 7th, 1984, Koch made public that he had found the bacteria that caused cholera. He wrote that the bacteria was not straight like other bacteria, but “a little bent, like a comma.” He also described how the bacteria lived better on damp surfaces or in water, which confirmed the earlier work of John Snow, who had stated that cholera was a water borne disease. Koch also noted that the cholera microbe was unable to survive in drying and weak acid solutions, which helped create solutions to battle the disease. In May, 1884 Koch and his team returned to Berlin where they were treated as national heroes. The Glasgow Herald, from Scotland, ran a story on Koch and his team soon after they returned, honoring there discovery. The microbe was named Vibrio Cholerae. 

Written by Mohsain Gill


Barua, Dhiman. “History of cholera.” In Cholera, pp. 1-36. Springer US, 1992.

Glasgow Herald (Glasgow, Scotland), Monday, October 13, 1884; Issue 245.

Howard-Jones, N. (1984). Robert Koch and the cholera vibrio: a centenary.Br Med J (Clin Res Ed), 288(6414), 379-381.

“150 Years of Cholera Epidemiology.” The Lancet 366, no. 9490 (2005): 957.

Pearse, J. S., and Jeffery A. Marston. “The Cholera at Newcastle-on-Tyne: The Statistics of Cases of Epidemic Cholera, 1853, Received at the Newcastle Dispensary; Together with Accounts of the Chemical and Microspical Examinations of the Excretions, and Observations upon the Pathology and Treatment.” The Lancet 63, no. 1588 (1854): 125-127.