Robert Koch

Robert Heinrich Hermann Koch (/ˈkɔːx/; German: [ˈkɔχ]; 11 December 1843 – 27 May 1910) was a celebrated German physician and pioneering microbiologist. As the founder of modern bacteriology, he is known for his role in identifying the specific causative agents of tuberculosis, cholera, and anthrax and for giving experimental support for the concept of infectious disease. In addition to his innovative studies on these diseases, Koch created and improved laboratory technologies and techniques in the field of microbiology, and made key discoveries in public health. His research led to the creation of Koch’s postulates, a series of four generalized principles linking specific microorganisms to specific diseases that remain today the "gold standard" in medical microbiology. As a result of his groundbreaking research on tuberculosis, Koch received the Nobel Prize in Physiology or Medicine in 1905.

Robert Koch was born in Clausthal, Hanover, Germany, on 11 December 1843, to Hermann Koch and Mathilde Julie Henriette Biewand. Koch excelled in academics from an early age. Before entering school in 1848, he had taught himself how to read and write. He graduated from high school in 1862, having excelled in science and maths. At the age of 19, Koch entered the University of Göttingen, studying natural science. However, after three semesters, Koch decided to change his area of study to medicine, as he aspired to be a physician. During his fifth semester of medical school, Jacob Henle, an anatomist who had published a theory of contagion in 1840, asked him to participate in his research project on uterine nerve structure. In his sixth semester, Koch began to conduct research at the Physiological Institute, where he studied succinic acid secretion. This would eventually form the basis of his dissertation. In January 1866, Koch graduated from medical school, earning honors of the highest distinction. In July 1867, Koch married Emma Adolfine Josephine Fraatz, and the two had a daughter, Gertrude, in 1868. Several years after his graduation in 1866, he worked as a surgeon in the Franco-Prussian War, and following his service, worked as a physician in Wollstein, Posen. From 1885 to 1890, he served as an administrator and professor at Berlin University. Koch’s marriage to Emma Fraatz ended in 1893, and later that same year, he married actress Hedwig Freiberg. Koch suffered a heart attack on 9 April 1910, and never made a complete recovery. On 27 May, only three days after giving a lecture on his tuberculosis research at the Prussian Academy of Sciences, Robert Koch died in Baden-Baden at the age of 66. Following his death, the Institute named its establishment after him in his honour. He was irreligious.

Anthrax

Robert Koch is widely known for his work with anthrax, discovering the causative agent of the fatal disease to be Bacillus anthracis. Koch discovered the formation of spores in anthrax bacteria that could remain dormant under specific conditions. However, under optimal conditions, the spores were activated and caused disease. To determine this causative agent, he dry-fixed bacterial cultures onto glass slides, used dyes to stain the cultures, and observed them through a microscope. Koch’s work with anthrax is notable in that he was the first to link a specific microorganism with a specific disease, rejecting the idea of spontaneous generation and supporting the germ theory of disease.

Koch's four postulates

Koch accepted a position as government advisor with the Imperial Department of Health in 1880. During his time as government advisor, he published a report in which he stated the importance of pure cultures in isolating disease-causing organisms and explained the necessary steps to obtain these cultures, methods which are summarized in Koch’s four postulates. Koch’s discovery of the causative agent of anthrax led to the formation of a generic set of postulates which can be used in the determination of the cause of most infectious diseases. These postulates, which not only outlined a method for linking cause and effect of an infectious disease but also established the significance of laboratory culture of infectious agents, are listed here:

1. The organism must always be present, in every case of the disease.
2. The organism must be isolated from a host containing the disease and grown in pure culture.
3. Samples of the organism taken from pure culture must cause the same disease when inoculated into a healthy, susceptible animal in the laboratory.
4. The organism must be isolated from the inoculated animal and must be identified as the same original organism first isolated from the originally diseased host.

Isolating pure culture on solid media

Koch began conducting research on microorganisms in a laboratory connected to his patient examination room. Koch’s early research in this laboratory proved to yield one of his major contributions to the field of microbiology, as it was there that he developed the technique of growing bacteria. Koch's second postulate calls for the isolation and growth of a selected pathogen in pure laboratory culture. In an attempt to grow bacteria, Koch began to use solid nutrients such as potato slices. Through these initial experiments, Koch observed individual colonies of identical, pure cells. Coming to the conclusion that potato slices were not suitable media for all organisms, Koch later began to use nutrient solutions with gelatin. However, he soon realized that gelatin, like potato slices, was not the optimal medium for bacterial growth, as it did not remain solid at 37 °C, the ideal temperature for growth of most human pathogens. As suggested to him by Walther and Fanny Hesse, Koch began to utilize agar to grow and isolate pure cultures, as this polysaccharide remains solid at 37 °C, is not degraded by most bacteria, and results in a transparent medium.

Cholera

Koch next turned his attention to cholera, and began to conduct research in Egypt in the hopes of isolating the causative agent of the disease. However, he was not able to complete the task before the epidemic in Egypt ended, and subsequently traveled to India to continue with the study. In India, Koch was indeed able to determine the causative agent of cholera, isolating Vibrio cholerae. The bacterium had originally been isolated in 1854 by Italian anatomist Filippo Pacini, but its exact nature and his results were not widely known.

Tuberculosis

Statue of Koch in Berlin

During his time as the government advisor with the Imperial Department of Health in Berlin in the 1880s, Robert Koch became interested in tuberculosis research. At the time, it was widely believed that tuberculosis was an inherited disease. However, Koch was convinced that the disease was caused by a bacterium and was infectious, and tested his four postulates using guinea pigs. Through these experiments, he found that his experiments with tuberculosis satisfied all four of his postulates. In 1882, he published his findings on tuberculosis, in which he reported the causative agent of the disease to be the slow-growing Mycobacterium tuberculosis. His work with this disease won Koch the Nobel Prize in Physiology and Medicine in 1905. Additionally, Koch's research on tuberculosis, along with his studies on tropical diseases, won him the Prussian Order Pour le Merite in 1906 and the Robert Koch medal, established to honour the greatest living physicians, in 1908.

In addition to being awarded a Nobel Prize, Koch was elected a Foreign Member of the Royal Society (ForMemRS) in 1897. His microbial postulates are named in his honour, Koch's postulates.

Koch's name is one of twenty-three, from the fields of hygiene and tropical medicine, featured on the frieze of the London School of Hygiene & Tropical Medicine building in Keppel Street, Bloomsbury.

A large marble statue of Koch stands in a small park known as Robert Koch Platz, just north of the Charity Hospital, in the Mitte section of Berlin.