Robert Koch

German bacteriologist

• Born: December 11, 1843
• Birthplace: Clausthal, Hanover (now Clausthal-Zellerfeld, Germany)
• Died: May 27, 1910
• Place of death: Baden-Baden, Germany

A pioneer bacteriologist, Koch was the first to prove definitively that specific microorganisms cause specific diseases. His identification of the bacterium that causes cholera enabled the virtual elimination of that disease in the Western world. He also isolated the causative agent of tuberculosis, making possible the containment of that once-deadly scourge, and he discovered the reproductive cycle of anthrax, providing for the successful combating of that disease.

Early Life

Born in the mining country of central Germany’s Harz Mountains, Robert Koch (kahk) was one of thirteen children of Hermann Koch and his wife, Mathilde Biewend. Hermann was a mining official and reasonably well-off, although provision for a large family taxed his resources. A timely promotion assisted him in educating Robert, a precocious child drawn to the study of nature, who was able to excel at the local gymnasium, or academic preparatory school. He went on to study at the nearby University of Göttingen. After a year of science and math, young Koch abandoned the idea of a teaching career and in 1863 transferred to the medical school at Göttingen, hoping that that field would allow him to pursue his love of science and travel. Koch’s greatest scientific mentor was Jacob Henle, an anatomy professor who had published on disease causation and who speculated that infection might be transmitted by living organisms. At that time, however, no medical school in the world offered courses in bacteriology.

In 1866, Koch received his medical degree, passed his medical examination, and went to Berlin, where for a few months he attended lectures by the famous Rudolf Virchow, author of the notion that disease is the result of disturbance of cell function in the body tissues. Koch, from the beginning of his career, was no mere medical practitioner concerned with diagnosis and treatment of disease but was a scientist interested in its causes.

After a brief internship at Hamburg General Hospital, where he learned about cholera at first hand, he returned home and in July, 1867, married Emmy Fraatz, a daughter of the mining superintendent of Clausthal. Koch and his wife then lived for about a year at Langenhagen, Hanover, where he served at a hospital for children with mental disabilities while he practiced medicine privately in the community. By the time the couple’s only child, Gertrud, was born in September of the following year, they were living at Niemegk, near Berlin. The young doctor’s practice did not flourish there, and Koch moved his family to Rakwitz, near Posen, where he became a successful country doctor.

During the Franco-Prussian War, Koch entered the Prussian Army Medical Corps and served in 1870 and 1871 in France, working both with the wounded and with soldiers afflicted with typhoid. He left the army and returned briefly to his patients at Rakwitz, but in 1872 he secured appointment as district physician for Wollstein, another small town in the province of Posen. It was from that area of lakes, woods, and fields that Koch moved into national and international acclaim. A ruralist would have called the setting idyllic; Koch’s later friend and admirer Élie Metchnikoff, a city dweller, referred to Wollstein as “a God-forsaken hole in Posen.” Nevertheless, it was the very rurality of Wollstein that provided Koch with his first great opportunity.

Life’s Work

Koch had become a mature physician with a lengthy and varied record of civilian and military experience. A smallish man with a bristling beard and round spectacles, he was the stereotypical Germanic scientist, and he longed to do more actual research than he could perform by examining algae and lesions with a handheld magnifying glass. A good microscope would have enabled him to peer more deeply into diseased tissue, but he believed that he could not afford such an instrument. His wife, Emmy, however, saved coins in a beer mug and surprised Koch with the money: The right man and the right research tool had come together at last. Like all men of genius, however, Koch was a driven man and made a poor companion. Emmy was neglected while her husband devoted most of his spare time to his laboratory, where he began by investigating the cause of anthrax—a very rural disease, a malady of grazing animals, primarily, but sometimes an ailment that could infect humans.

During the 1860’s, the French physician-researcher Casimir-Joseph Davaine had discovered that a bacterium was the cause of anthrax. He called the rodlike microorganism “bactéridie” (later known to science as Bacillus anthracis), but he was not able to ascertain how the disease was transmitted or how the bacteria, which did not seem to be very long-lived, managed to survive between hosts.

Koch first verified Davaine’s work by using sterilized wood splinters to inject anthrax bacilli into the tails of mice that he kept in cages in his laboratory. When the first mouse died, a drop of its blood was injected into a second mouse, and so on, until after eight mice the conclusion had to be reached that the poison was a living, self-perpetuating entity. A chemical poison would eventually have become so attenuated as to lose its potency. To grow his anthrax bacilli without contamination from other bacteria, Koch invented the hanging-drop technique. He ground out a depression in a thick glass slide, put a drop of blood containing anthrax microbes on a thin glass coverslip, put sealant around the edges of both sterile slides, placed the thick one over the thin one, and quickly inverted the pair, causing the drop to hang suspended over the depression. As a culture medium for the bacilli, he used liquid from the interior of the eye.

Only about one hundred miles from Wollstein was the large university city of Breslau in Silesia, and there the renowned botanistFerdinand Julius Cohn had been working with bacteria. He had predicted that anthrax bacilli might form small eggs or spores. Koch clearly observed the spores, as he had been keeping his slides at body temperature, thus allowing the bacteria to develop through their life cycle though outside a host. Koch noted that in the inert or spore stage, anthrax bacilli, normally quick to perish when not in a warm host, could survive for years and be destroyed only by burning. He found that the spores formed only when the host died but was still warm.

Koch wrote to Cohn at Breslau in 1876 and arranged to demonstrate his techniques and findings. Koch packed his equipment and animals and treated Cohn and other scientists to a history-making exhibition, during which the pathologist Julius Cohnheim was said to have rushed from the room in great excitement to summon his students to see the masterful work being demonstrated. Though self-taught, Koch handled his equipment like a master scientist, and his three-day re-creation of his experiments left no room for doubt that he had discovered the true etiology of anthrax. He was the first to prove that a microscopic one-celled organism caused a disease.

Cohn and Cohnheim became Koch’s champions in the academic community. Cohn, in his biology journal, published Koch’s paper on anthrax, and Koch’s fame began to spread. While the Breslau scientists tried to find government support for Koch, he had to continue his researches in his tiny laboratory—a laboratory that Koch could hardly suspect would one day be turned into a museum. Koch, meanwhile, was making a definitive record of his observations by purchasing a special camera that he fitted to his microscope—a pioneer technique on which he wrote in 1877 in another article in Cohn’s journal of biology. In the same article, he touted the use of the still fairly new aniline dyes for staining bacterial cultures on slides to make organisms contrast with the background. He had not been the first to employ the technique, but he was one of the earliest to advocate it.

By that time, the news of Koch’s work had spread not only around Germany but also over all the world. Even the hidebound German bureaucracy began to pay attention. In 1879, Koch was given a post at Breslau, but it had an insufficient salary, so the Koch family returned to Wollstein. Finally, the following year, Cohnheim succeeded in having Koch named as government counselor to the Imperial Bureau of Health in Berlin. A country doctor no more, Koch was given a laboratory, two assistants, and financial support.

It was after moving into his new laboratory in the capital city that Koch innocently made a rather rural discovery: He saw bacterial colonies growing on a slice of leftover boiled potato. Several different kinds were on the slice, and it struck Koch that a solid medium would provide an excellent way to keep separate the bacteria he was culturing. After a while, he abandoned cooked potato slices and employed a mixture of gelatin and beef broth, which he allowed to set in petri dishes. Louis Pasteur, who always cultured microorganisms in a souplike mixture, had a difficult time separating the desired microbes.

In Berlin, Koch concentrated on finding the agent causing tuberculosis, a slow but usually fatal endemic disease that was at its height during the late nineteenth century. Tubercle bacilli are much smaller and harder to grow than those of anthrax, but Koch persisted and produced a special blood-serum jelly to culture tuberculosis outside the body. Although he did prove that the tubercle bacillus caused the disease, Koch’s vaunted tuberculin, a serum designed to cure tuberculosis in nonterminal patients, proved ineffective. Nevertheless, tuberculin can be used to diagnose the disease and is thus quite valuable.

Koch’s greatest success story was the discovery of the cause of cholera—a horrible and usually fatal disease whose deadly epidemics were the terror of nineteenth century Europe and America. In 1883, cholera spread into Egypt and threatened to cross into Europe. To prevent this, the governments of France and Germany sent their best scientists to Alexandria: a French team consisting of Pasteur’s top men and a German squad led by Koch himself. They searched for a microbe guilty of causing the feared cholera, and Koch was rather sure that he had located it. Then the epidemic left Egypt as mysteriously as it had come, and Europe was temporarily safe, but no one knew why.

Back in Berlin, Koch asked the government to send him to Calcutta, in eastern India, to find the disease in its permanent home. There, Koch and his assistants in early 1884 positively identified the vibrio bacillus as the cause and found that it was transmitted by water and other substances polluted with fecal matter. When the German scientists arrived home in May, they were greeted as conquering heroes. With lavish ceremony, the German Emperor William I personally decorated Koch with the Order of the Crown, with Star, while the Reichstag voted the scientist a large monetary gift.

Significance

Robert Koch shares with Pasteur the honor of founding modern medical bacteriology, but, in employment of solid culture media, discovery of improved sterilization by steam, use of staining techniques, and other innovations, he built the modern bacteriological laboratory. Koch’s name is permanently associated with the conquest or taming of anthrax, cholera, and tuberculosis, but he did much other work. He always had a yearning to travel, frustrated in earlier years by family responsibilities. Leaving his perennial and only partially successful work on tuberculosis, Koch worked on malaria in Italy, rinderpest in South Africa, sleeping sickness and tick fever in German East Africa, and bubonic plague in northern India. He identified the rat and its flea as vectors of the plague, but it remained for Koch’s Japanese disciple Kitasato Shibasaburo to isolate the actual microbe.

Koch scandalized Victorian mores in 1892 when, his marriage failing, he divorced his first wife and married a young actor, Hedwig Freiburg. Many of his biographers deliberately omitted any mention of the occurrence, as they themselves were scandalized—a comment on the strict middle-class morality of the late nineteenth century. Koch was awarded the Nobel Prize in Physiology or Medicine in 1905, primarily for his work on tuberculosis. It was an ultimate vindication for great efforts that bore fruit in many different ways that he was given such recognition for a disease that he had not managed to kill.

Bibliography

Brock, Thomas D. Robert Koch: A Life in Medicine and Bacteriology. Madison, Wis.: Science Tech, 1988. Reprint. Washington, D.C.: ASM Press, 1999. Biography focusing on Koch’s medical career, drawing upon his published work, correspondence, and nineteenth century bacteriological literature.

Daniel, Thomas M. Pioneers of Medicine and Their Impact on Tuberculosis. Rochester, N.Y.: University of Rochester Press, 2000. This history of tuberculosis and its treatment includes a chapter on Koch’s pioneering work in bacteriology.

De Kruif, Paul. Microbe Hunters. New York: Harcourt, Brace & World, 1950. This readable yet detailed account has a lengthy chapter on “Koch: The Death Fighter.” De Kruif’s entertaining style makes the sometimes arcane world of microbiology accessible to the general reader.

Dormandy, Thomas. The White Death: A History of Tuberculosis. New York: New York University Press, 2000. This history of tuberculosis includes a portrait of Koch and his role in isolating the cause of the disease.

Dubos, René. The Unseen World. New York: Rockefeller Institute Press, 1962. This work has a large section on Koch’s life and contributions, including several interesting photographs. The book is an excellent and easily understandable introduction to microbiology and gives great credit to Koch as a founder of the science.

Fox, Ruth. Great Men of Medicine. New York: Random House, 1947. This book has a lengthy, thorough, and entertaining chapter on Koch. Fox concentrates on the early and middle portions of the pathologist’s career.

Metchnikoff, Élie. The Founders of Modern Medicine. New York: Walden, 1939. This outstanding volume by a man who was himself a famous medical scientist and who knew Koch personally provides a rare and valuable look at Koch’s scientific and personal lives.

Riedman, Sarah R., and Elton T. Gustafson. Portraits of Nobel Laureates in Medicine and Physiology. New York: Abelard-Schuman, 1963. Contains an excellent chapter on Koch plus a considerable amount of discussion of him in other chapters relating to researchers who were indebted to or in contact with him.

Stevenson, Lloyd G. Nobel Prize Winners in Medicine and Physiology, 1901-1950. New York: Henry Schuman, 1953. This volume concentrates on and gives a good account of Koch’s work on tuberculosis, as Koch’s labor in this area was what won for him the Nobel Prize.