Frustrated by unfulfilled big dreams of high adventure, Robert Koch, a German physician, was destined for smallness, as a pioneer of modern microbiology.
Dr. Koch (pronounced ‘Coke’) was not merely unhappy that his life as a 19th century physician was not action packed; he was profoundly frustrated by his inability to do more than ease the suffering of the patients he was helpless to save. How is it possible to cure sick patients without understanding the actual cause of their illnesses?
Perhaps to help distract him from his unhappiness, his wife Emmy purchased a microscope for Robert as a gift. Although not educated as a scientific researcher, armed with that microscope and his dogged determination, Koch carried out experiments that transformed our understanding of infectious disease.
* Koch’s Experiments with Anthrax *
As a country doctor, Koch was well aware of the difficulties faced by European farmers. Anthrax, a strange illness, was sweeping across Europe killing livestock. A lamb, apparently healthy at sunrise, might, by sunset, be stone dead, its blood turned black. And this disease did not confine itself to livestock; humans interacting with these animals were also at risk of becoming ill.
So Koch started using his microscope to look at the tissue of animals that had died from anthrax, and found strange microscopic rods and threads within the samples that he examined. Were these rods alive? Were they the cause of the illness? Tissue from healthy sheep and cows did not contain these mysterious threads.
Koch began to experiment with ways to isolate and grow these microbes. After learning to grow the anthrax rods in sterile fluid from the eye of an ox, he began to infect mice with small samples of the microscopic rods originally isolated from dead farm animals. The infected mice always died, and upon dissection, were found to be teeming with anthrax rods. Koch had single-handedly proven that a specific microbe caused a specific disease.
* Growing, Isolating and Viewing Bacteria *
His breakthrough with anthrax eventually brought Koch the funding and facilities to continue his research on microbes. But anthrax are relative giants among bacteria. Koch was faced with the problem of how to isolate and tell the difference between, many bacteria that are much smaller and similar to each other in appearance.
Initially, Koch would spread bacterial samples on a slice of potato or sample of gelatin and then wait for the bacterial populations to increase. In large enough numbers they visible, each bacterial colony, or single group of bacteria, having arisen from one initial bacterial cell. He then refined this technique for growing bacteria with the use of agar-filled Petri dishes, and began to use simple stains to color the bacterial cells, making them easier to see.
* Koch’s Postulates *
Koch then went on to isolate Mycobacterium tuberculosis, the causative agent of tuberculosis. In the publication of his results, he put forth the series of steps necessary to prove the cause of any infectious disease. These are now known as Koch’s Postulates and are held to be one of his most important contributions to the study of microbiology.
Koch’s Postulates are as follows:
1. The suspected causative agent of a disease must be found in every case, and absent in healthy individuals.
2. The agent must then be isolated and grown outside the host (i.e. cultivated in a laboratory environment).
3. When a healthy, susceptible host is inoculated with the agent, the host must develop the same disease.
4. That same agent must then be reisolated from the experimental host.
* References *
Bauman, R. (2007). Microbiology with Diseases by Taxonomy. Pearson Benjamin Cummings.
DeKruif, P. (1926). Microbe Hunters. Harcourt, Inc.
