Robert Koch was born on December 11, 1843 in the mountains of Germany. His father was an engineer in the town of Clausthal, where silver and other precious metals had been mined since the Middle Ages. By the time he was five years old, Robert had taught himself to read, using the newspaper. In school, he was excellent at physics and math, but especially loved biology.

When Robert was nineteen, he went to medical school. His anatomy professor Jacob Henle introduced him to the revolutionary idea that diseases were caused by living organisms too small to see without a microscope. After serving in the military during the Franco-Prussian war, Robert began doing research that would change the world forever.

At the time, a disease called anthrax plagued farm animals, such as cattle, sheep, and goats. Humans could also get sick and die from the disease. Working from a lab he had set up in his house, Robert Koch identified a rod-shaped bacterium in infected animals and demonstrated that it caused the dreaded disease. By infecting mice with anthrax bacteria, he also proved that bacteria-laden blood from animals sick with anthrax can infect other animals. It was the first time that anyone had ever linked a specific microorganism to one specific disease.

To isolate pure cultures containing only one type of bacteria, Koch had to grow individual “colonies” arising from single cells. To grow colonies, Koch spread microbes on potatoes and shallow dishes filled with a jelly-like substance called gelatin. Eventually, he switched to using petri dishes filled with agar growth medium. (See Lab 10.)

After that, Dr. Koch published a list of rules, called postulates, which could be used to prove which organisms caused certain diseases. His rules involved isolating one type of microbe from a diseased animal and using that same microbe to infect another animal. If he observed the same symptoms in that animal, he would then attempt to isolate the same microbe from the newly-infected animal. Using these rules, Koch discovered which microbes caused two diseases especially dangerous to humans: tuberculosis and cholera.

In 1906, Robert Koch was awarded the Nobel Prize in Physiology or Medicine. His work was the foundation for modern microbiology and infectious disease medicine.

Today, scientists know more about microbiology and use modern technology, such as DNA sequencing, to help identify disease-causing organisms.