Robert Koch Identifies the Bacteria that Cause Anthrax, Tuberculosis, and Cholera

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Robert Koch Identifies the Bacteria that Cause Anthrax, Tuberculosis, and Cholera

Presentation Speech for the Nobel Prize in Physiology or Medicine, 1905


By: K. A. H. Mörner

Date: December 10, 1905

Source: Nobel Lectures, Physiology or Medicine 1901–1921. Amsterdam: Elsevier, 1967. Available online at 〈〉 (accessed September 10, 2005).

About the Author: Count K. A. H. Mörner was a chemist, professor, and Rector of the Royal Caroline Institute in Stockholm, Sweden, in 1905 when he presented the Nobel Prize in Medicine or Physiology to Robert Koch.


Along with Louis Pasteur, Robert Koch is regarded as being one of the two founders of bacteriology (the study of bacteria).

It was Koch's training as a physician that led to his seminal research. In 1872, Koch became the District Medical Health Officer in Wollstem, Germany. There, he began to investigate the cause of anthrax. Previous research by Casmir-Joseph Davaine had shown that the occurrence of anthrax in sheep was associated with the appearance of rod-like bodies in the blood.

Koch was able to grow the bodies on a growth medium, now known as Bacillus anthracis, demonstrating that they were living organisms. Furthermore, his light microscopy observations of oval translucent bodies inside the organisms represented one of the earliest descriptions of the dormant spore of the anthrax bacillus (which, in September 2001, became infamous in the United States). Later research by Koch showed that the spores could cause the disease even after being kept in a dried state for years. This work laid the foundation for unraveling the life cycle of anthrax bacillus.

As part of his microscopy studies of bacteria, Koch demonstrated the usefulness of stains such as methyl violet in more definitively revealing the presence of bacteria. This technique, along with his postulates, was crucial in allowing Koch to implicate a bacillus later dubbed Mycobacterium tuberculosis, as the cause of tuberculosis in 1882.

Koch also investigated an outbreak of cholera in Egypt, and a later Indian outbreak, where his research implicated a comma-shaped bacillus as the cause of the disease. Future investigators confirmed that this bacterium, Vibrio cholerae, was, indeed, the cause of cholera. Koch demonstrated that the microbe could be transmitted from person to person via contaminated drinking water, food, and clothing.


Your Majesty, Your Royal Highnesses, Ladies and Gentlemen.

The Staff of the Royal Caroline Institute takes great pleasure in giving this year's Nobel Prize for Medicine to the man who takes precedence among those now alive as a pioneer in bacteriological research, the prize being awarded to Geheimrat Robert Koch for his work and discoveries concerning tuberculosis.

… To make Koch's significance in the development of bacteriology clear, one must take a look at the situation with which Koch was confronted when he made his appearance. Pasteur had indeed already published by then his epoch-making work, which laid the foundations of bacteriology, and medical art had already gathered in one very beneficial fruit which stemmed from this work, namely the antiseptic method of treating wounds proposed by Lister. However, the trail was yet to be blazed, which bacteriological research has followed with such success during recent decades, to discover the causes of individual diseases and to look for the means of combating them. Koch was a pioneer in this.

For two diseases namely anthrax and typhus recurrens in which micro-organisms of a particularly characteristic appearance were relatively easy to demonstrate, it was agreed that the latter were the causes of these diseases. Otherwise the causal relationship between bacteria and diseases was obscure. It is true that there were good grounds for supposing that certain other diseases were caused by micro-organisms. But detailed knowledge concerning this was lacking, and experimental findings were very divergent. So, for instance, it was not established whether normal healthy organs contained bacterial germs. This was certainly contested by various prominent investigators, but on the other hand this view was defended by other also prominent authors. Then the question still remained open of whether bacteria observed in a disease were also its cause, or whether their development should rather be considered a result of the pathological process. In addition, in studying one and the same type of disease various investigators looked in vain for bacteria in the organism, while others, however, found them. Moreover, bacteria, which various investigators had observed in a particular disease, were often of a different appearance, so that there was reason for doubting that they were the specific and genuine cause of the disease. On the other hand, in widely differing types of disease, bacteria were met with which, as far as was known, were of one and the same kind, and this gave still more cause for adopting a position of doubt with regard to the causal relationship between these bacteria and the pathological process. It was indeed difficult to imagine that the bacteria discovered had to be regarded as the essential causes of disease, since it looked partly as if the same disease could be caused by different bacteria, and partly as if the same bacteria could produce different diseases. It was easier to suppose that the bacteria all had the property of facilitating the development of the disease by exercising an influence on the organism. The uncertainty was that much greater since the experiments which were carried out often could not demonstrate whether a real bacterial invasion of the organism had taken place.

In 1876 Koch entered the field of bacteriological research with an investigation of anthrax, and two years later he produced his classical investigations into diseases from wound infections. With the views set out there and the way he formulated the questions, he had a fundamental effect on the further development of bacteriology, and the ideas he expressed there recur as a leading motive in his subsequent research and form the foundation of modern bacteriology, as they do of the axioms of hygiene which are derived from it.

He stressed that, if bacteria caused a disease, then they must always be demonstrable in it, and they should develop in a way such that this would account for the pathological process.

He further stressed that the capacity to produce disease could not be a general property of bacteria or one common to them all. On the contrary it should be expected in this respect to find specific properties distinguishing individual bacteria. Even if they resemble other bacteria in their form, etc., they must still be different from one another by virtue of this biological property: in other words, every disease must have its special bacterium, and to combat the disease, it would be necessary to look for clues in the biology of the bacterium. Koch therefore not only set himself the task of examining the problem of whether diseases were caused by bacteria, but also endeavoured to discover the special micro-organisms of the particular diseases and to get to know more about them: this was a problem which, in the circumstances then prevailing, seemed to offer very little hope of being solved. In the way Koch solved this problem he was just as much, if not more, of a pioneer, then he already was in the abovementioned precision which he had given to the formulation of the problem.

To start with, developing a general methodology is as valuable as finding the correct technique for every special case. Koch's genius has blazed new trails in this respect and has given present-day research its form. To give a detailed description of this is beyond the scope of this account. I only want to mention that he had moreover already given a significant development to techniques in staining and microscopic investigation as well as in the field of experiment in his earliest work. Shortly after this he produced the important method, which is still generally the usual one, of spreading the material under investigation in a solid nutrient medium to allow each individual among the micro-organisms present to develop into a fixed colony, from which it is possible, in further research, to go on to obtain what is known as a pure culture.

Shortly after the publication of his investigations into diseases from wound infections Koch was appointed to the new Institution, the "Gesundheitsamt" (Department of Health), in Berlin. There he started work on some of the most important human diseases, namely, tuberculosis, diphtheria and typhus. He worked on the former one himself. The two latter investigations he left to his first two pupils and assistants, Loeffler and Gaffky. For all three diseases the specific bacteria were discovered and studied in detail….

Through the perfection he gave to methods of culturing and identifying micro-organisms, he has been able to carry out his work with regard to disinfectants and methods of disinfection so important for practical hygiene, and advice concerning the early detection and combating of certain epidemic diseases such as cholera, typhus and malaria.

Now I move over to a brief account of the series of investigations which is the object of the present award.

The idea that tuberculosis is infectious goes back a long way to Morgagni. Already before Koch had started his investigations into this disease, it had been possible to show that tuberculosis may be inoculated into animals. It was not, however, proved that it was caused by a micro-organism, and such an interpretation was contested by very distinguished investigators.

Koch made his first communication concerning his research on tuberculosis in a lecture given on March 24, 1882 to the Physiological Society of Berlin. This lecture covers scarcely two pages of print, yet in it are given the proofs of the discovery of the tubercle bacillus and the description of its chief characteristics. The method for staining it in the affected tissue is described there, its constant occurrence in tuberculous processes in man and beast is mentioned, the procedure for producing pure cultures of it is described, and information is given concerning typical and positive results of inoculating the bacillus in animals. It was emphasized there, in addition, that the bacillus is dependent on the living organism for its development and multiplication, and that hence tuberculous infection is derived primarily from the expectorations of consumptives, and that it can probably also be caused by cattle suffering from "pearl disease."…

Seldom has an investigator been able to comprehend in advance with such clear-sightedness a new, unbroken field of investigation, and seldom has someone succeeded in working on it with the brilliance and success with which Robert Koch has done this. Seldom have so many discoveries of such decisive significance to humanity stemmed from the activity of a single man, as is the case with him….

Geheimrat Robert Koch. In announcing that the Staff of Professors of the Royal Caroline Institute has awarded you this year's Nobel Prize in Medicine for your work and discoveries concerning tuberculosis, I bring you the Staff's homage….

By your pioneering research you have found out the bacteriology of tuberculosis, and written your name for ever in the annals of medicine.


Koch's legacy lies in establishing rigorous scientific methods to examine samples, identify the presence of microorganisms, and implicate those bacteria as the cause of a particular disease. His training as a physician and his expertise as a researcher were perfectly suited to the task.

Koch built upon the work of Louis Pasteur, who showed that disease-causing microbes could potentially be grown in cultures outside of the body. Koch perfected what came to be known as the pure culture technique.

Another key achievement was Koch's formulation of a series of rules, or postulates, which, if achieved, were definitive proof of an organism's role in a disease. Koch's postulates stated that an organism was the cause of a disease if: It was always recoverable in every instance of the disease; When obtained from the body, the organism could be maintained in a pure culture for at least several generations; The disease could be reproduced in experimental animals by the introduction of a sample of a pure culture that had not been directly obtained from a disease sample; The organism could be recovered from the sick animal and re-established in pure culture.

While viruses were subsequently found to deviate from these rules, Koch's postulates have proven remarkably adept at pinpointing the cause of diseases, and in guiding the search for cures. By 1900, only a few decades after Koch had developed these research methodologies, twenty-one microorganisms had been identified as the cause of twenty-one different diseases.



Brock, Thomas. Robert Koch: A Life in Medicine and Bacteriology. Washington, D.C.: American Society for Microbiology, 2000.

Tracy, Kathleen. Robert Koch and the Study of Anthrax. Hockessin, Del.: Mitchell Lane Publishers, 2004.

Web sites

The Nobel Foundation. "The Nobel Prize in Physiology or Medicine, 1905." 〈〉 (accessed October 11, 2005).

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Robert Koch Identifies the Bacteria that Cause Anthrax, Tuberculosis, and Cholera

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