Robert Koch

Heinrich Hermann Robert Koch (/kɒx/ KOKH; German: [ˈʁoːbɛʁt kɔx] ^ⓘ; 11 December 1843 – 27 May 1910) was a German physician and microbiologist. As the discoverer of the specific causative agents of deadly infectious diseases including tuberculosis, cholera and anthrax, he is regarded as one of the main founders of modern bacteriology. As such he is popularly nicknamed the father of microbiology (with Louis Pasteur), and as the father of medical bacteriology. His discovery of the anthrax bacterium (Bacillus anthracis) in 1876 is considered as the birth of modern bacteriology. Koch used his discoveries to establish that germs "could cause a specific disease" and directly provided proofs for the germ theory of diseases, therefore creating the scientific basis of public health, saving millions of lives. For his life's work Koch is seen as one of the founders of modern medicine.

While working as a private physician, Koch developed many innovative techniques in microbiology. He was the first to use the oil immersion lens, condenser, and microphotography in microscopy. His invention of the bacterial culture method using agar and glass plates (later developed as the Petri dish by his assistant Julius Richard Petri) made him the first to grow bacteria in the laboratory. In appreciation of his work, he was appointed to government advisor at the Imperial Health Office in 1880, promoted to a senior executive position (Geheimer Regierungsrat) in 1882, Director of Hygienic Institute and Chair (Professor of hygiene) of the Faculty of Medicine at Berlin University in 1885, and the Royal Prussian Institute for Infectious Diseases (later renamed Robert Koch Institute after his death) in 1891.

The methods Koch used in bacteriology led to the establishment of a medical concept known as Koch's postulates, four generalized medical principles to ascertain the relationship of pathogens with specific diseases. The concept is still in use in most situations and influences subsequent epidemiological principles such as the Bradford Hill criteria. A major controversy followed when Koch discovered tuberculin as a medication for tuberculosis which was proven to be ineffective, but developed for diagnosis of tuberculosis after his death. For his research on tuberculosis, he received the Nobel Prize in Physiology or Medicine in 1905. The day he announced the discovery of the tuberculosis bacterium, 24 March 1882, has been observed by the World Health Organization as "World Tuberculosis Day" every year since 1982.

Koch was born in Clausthal, Germany, on 11 December 1843, to Hermann Koch (1814–1877) and Mathilde Julie Henriette (née Biewend; 1818–1871). His father was a mining engineer. He was the third of thirteen siblings. He excelled academically from an early age. Before entering school in 1848, he had taught himself how to read and write. He completed secondary education in 1862, having excelled in science and math.

At the age of 19, in 1862, Koch entered the University of Göttingen to study natural science. He took up mathematics, physics and botany. He was appointed assistant in the university's Pathological Museum. After three semesters, he decided to change his area of study to medicine, as he aspired to be a physician. During his fifth semester at the 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. This research won him a research prize from the university and enabled him to briefly study under Rudolf Virchow, who was at the time considered "Germany's most renowned physician". In his sixth semester, Koch began to research at the Physiological Institute, where he studied the secretion of succinic acid, which is a signalling molecule that is also involved in the metabolism of the mitochondria. This would eventually form the basis of his dissertation. In January 1866, he graduated from the medical school, earning honours of the highest distinction, maxima cum laude.

Robert Koch is widely known for his work with anthrax, discovering the causative agent of the fatal disease to be Bacillus anthracis. After officially becoming a district physician in Wollstein (today's Wolsztyn), Poland, in 1872, Robert began to delve into the disease called Anthrax. Near Wollstein, anthrax disease was regularly taking the lives of humans and livestock without evidence explaining why. Eventually, in 1876, Koch was able to make an incredible discovery that anthrax was triggered by one singular pathogen. Koch's discovery of the dormant stage, the anthrax spores, allowed him to successfully unravel the mystery behind the anthrax disease. By gaining a better understanding of this pathogen, he was able to shed light on the bacterium's remarkable resistance to environmental factors ("Robert Koch – Nobel Lecture" 2018). This groundbreaking achievement marked Koch as the pioneer scientist to discover that a microscopic organism was causing a disease to spread. His findings were especially impressive as they were done in a poorly equipped laboratory in Wollstein.

He published the discovery in a booklet as "Die Ätiologie der Milzbrand-Krankheit, Begründet auf die Entwicklungsgeschichte des Bacillus Anthracis" (The Etiology of Anthrax Disease, Based on the Developmental History of Bacillus Anthracis) in 1876 while working at in Wöllstein. His publication in 1877 on the structure of anthrax bacterium marked the first photography of a bacterium. He discovered the formation of spores in anthrax bacteria, which 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. His 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.

After graduation in 1866, Koch briefly worked as an assistant in the General Hospital of Hamburg. In October of that year, he moved to Idiot's Hospital of Langenhagen (as it was known in English, later named KRH Psychiatrie Langenhagen), near Hanover, as a junior physician. In 1868, he moved to Neimegk and then to Rakwitz in 1869. As the Franco-Prussian War started in 1870, he enlisted in the German army as a volunteer surgeon in 1871 to support the war effort. He was discharged a year later and was appointed as a district physician (Kreisphysikus) in Wollstein in Prussian Posen (now Wolsztyn, Poland). As his family settled there, his wife gave him a microscope as a birthday gift. With the microscope, he set up a private laboratory and started his career in microbiology.