Heinrich Hermann Robert Koch (born December 11, 1843; died May 27, 1910) was a German doctor and scientist who studied tiny living things called microbes. He received the 1905 Nobel Prize in Physiology or Medicine for his research on tuberculosis, a serious disease that harms the lungs.

Koch discovered the germs that cause dangerous diseases such as tuberculosis, cholera, and anthrax. Because of this, he is considered one of the key scientists who helped create modern bacteriology, the study of bacteria. He is sometimes called the "father of microbiology" along with Louis Pasteur, and also the "father of medical bacteriology." His discovery of the anthrax bacterium (called Bacillus anthracis) in 1876 marked the start of modern bacteriology. Koch showed that germs can cause specific diseases, which supported the germ theory of disease. This theory helped improve public health and saved many lives. His work is seen as a major part of the development of modern medicine.

While working as a doctor, Koch created new methods in microbiology. He was the first to use tools like the oil immersion lens, condenser, and microphotography in microscopes. He also developed a way to grow bacteria in the laboratory by using agar and glass plates. This method was later improved by his assistant, Julius Richard Petri, and became known as the Petri dish. Because of his contributions, Koch was given important roles, including government advisor at the Imperial Health Office in 1880, a senior position (Geheimer Regierungsrat) in 1882, and leadership roles at the Hygienic Institute and Berlin University in 1885. In 1891, he became the director of the Royal Prussian Institute for Infectious Diseases, which was later renamed the Robert Koch Institute after his death.

Koch’s work led to the creation of "Koch’s postulates," four rules that help scientists link germs to specific diseases. These rules are still used today and influence other scientific methods, such as the Bradford Hill criteria. Later in his career, Koch discovered a substance called tuberculin, which was found to be ineffective for treating tuberculosis but later used to diagnose the disease. The day Koch announced the discovery of the tuberculosis bacterium, March 24, 1882, is celebrated by the World Health Organization as "World Tuberculosis Day" every year since 1982.

Early life and education

Robert Koch was born on December 11, 1843, in Clausthal, Germany, to Hermann Koch (1814–1877) and Mathilde Julie Henriette (née Biewend; 1818–1871). His father worked as a mining engineer. Koch was the third of thirteen children in his family. He showed strong academic abilities early in life. Before starting school in 1848, he learned to read and write on his own. He finished secondary school in 1862, where he performed well in science and mathematics.

In 1862, at age 19, Koch began studying natural science at the University of Göttingen. He focused on subjects such as mathematics, physics, and botany. He became an assistant at the university’s Pathological Museum. After three semesters, he switched to studying medicine because he wanted to become a doctor. During his fifth semester at medical school, Jacob Henle, an anatomist who wrote about how diseases spread in 1840, invited Koch to join his research on the nerves in the uterus. This work earned Koch a research prize and allowed him to study briefly under Rudolf Virchow, who was known as "Germany’s most well-known physician" at the time. In his sixth semester, Koch started research at the Physiological Institute, where he studied succinic acid, a signaling molecule involved in mitochondrial metabolism. This research became the foundation of his dissertation. In January 1866, Koch graduated from medical school with the highest honors, earning the distinction of maxima cum laude.

Career

After graduating in 1866, Koch worked briefly as an assistant at the General Hospital in Hamburg. In October of that year, he moved to the Idiot’s Hospital in Langenhagen (later renamed KRH Psychiatrie Langenhagen) near Hanover, where he worked as a junior physician. In 1868, he moved to Neimegk and then to Rakwitz in 1869. When the Franco-Prussian War began in 1870, Koch joined the German army as a volunteer surgeon in 1871 to help with the war effort. He left the army a year later and was appointed as a district physician (Kreisphysikus) in Wollstein, Prussian Posen (now Wolsztyn, Poland). His family moved there, and his wife gave him a microscope as a birthday gift. Using the microscope, Koch created a private laboratory and began his work in microbiology.

Koch conducted research on microorganisms in a laboratory connected to his patient examination room. His early studies led to one of his major contributions to microbiology: developing a method to grow bacteria. He also successfully isolated and grew specific disease-causing microbes in pure laboratory cultures. Koch’s discovery of the anthrax bacillus (later named Bacillus anthracis) impressed Ferdinand Julius Cohn, a professor at the University of Breslau (now the University of Wrocław). Cohn helped Koch publish the discovery in 1876. Cohn, who had founded the Institute of Plant Physiology, invited Koch to present his findings there in 1877. In 1879, Koch was transferred to Breslau as a district physician. A year later, he moved to Berlin when he was appointed a government advisor at the Imperial Health Office, where he worked from 1880 to 1885. After discovering the tuberculosis bacterium, Koch was promoted to Geheimer Regierungsrat, a senior government position, in June 1882.

In 1885, Koch was appointed as an administrator and professor at Berlin University. He became Director of the Hygienic Institute and Chair (Professor of Hygiene) in the Faculty of Medicine. In 1891, he gave up his professorship and became director of the Royal Prussian Institute for Infectious Diseases (now the Robert Koch Institute), which included a clinical division and research facilities. Koch accepted difficult conditions, as the Prussian Ministry of Health required that any inventions he made would belong to the government, and he would not receive payment. Koch lost the right to apply for patents. In 1906, he traveled to East Africa to study a cure for trypanosomiasis (sleeping sickness). He established the Bugula research camp, where up to 1,000 people per day were treated with the experimental drug Atoxyl.

Scientific contributions

Robert Koch is well known for his work on anthrax, a deadly disease caused by the bacterium Bacillus anthracis. After becoming a district physician in Wollstein (now Wolsztyn), Poland, in 1872, Koch began studying anthrax. Near Wollstein, anthrax was killing people and animals, but no one knew why. In 1876, Koch discovered that a single pathogen caused the disease. He found that anthrax spores, which can remain inactive for long periods, were responsible. This discovery helped explain how anthrax spreads and why it is hard to destroy in the environment. Koch’s work showed that a microscopic organism could cause disease, which was a major scientific breakthrough. His research was done in a simple laboratory in Wollstein.

In 1876, Koch published his findings in a booklet titled The Etiology of Anthrax Disease, Based on the Developmental History of Bacillus Anthracis. In 1877, he published a study that included the first photograph of a bacterium. He discovered that anthrax bacteria can form spores, which stay inactive under certain conditions. When conditions are right, the spores become active and cause disease. To study this, Koch used glass slides, dyes, and a microscope. His work proved that a specific microorganism causes a specific disease, supporting the idea that germs, not spontaneous generation, cause illness.

Koch made two important improvements in microscopy. He was the first to use an oil immersion lens and a condenser to see tiny objects more clearly. He also used photography (microphotography) to observe bacteria. Koch introduced methods to stain bacteria using dyes like methylene blue and Bismarck brown. To grow bacteria, he tried using potato slices but later switched to gelatin. However, gelatin melted at body temperature (37°C) and was broken down by some bacteria. In 1881, Koch’s assistant, Walther Hesse, suggested using agar, a substance that stays solid at 37°C and is not easily broken down by bacteria. Koch began using agar to grow and isolate pure cultures of bacteria.

In 1881, Koch published a booklet titled Methods for the Study of Pathogenic Organisms, often called the "Bible of Bacteriology." He described a method to grow bacteria on agar-coated glass slides. A thin layer of gelatin was used to solidify the agar, and bacterial samples were spread evenly. A moist chamber, made of a glass dish with a lid, helped keep the cultures safe from contamination. Koch’s method allowed scientists to observe bacterial growth clearly.

Koch demonstrated his plating method at the Seventh International Medical Congress in London in 1881. Louis Pasteur praised the method, calling it "a great progress." Using Koch’s techniques, his students discovered new bacteria, such as those that cause glanders (Burkholderia mallei), diphtheria (Corynebacterium diphtheriae), and typhoid (Salmonella enterica). Koch’s assistant, Julius Richard Petri, improved the method in 1887 by using a circular glass dish directly instead of a glass plate. This became known as the Petri dish.

In the 1880s, Koch worked as a government advisor for the Imperial Health Agency in Berlin and studied tuberculosis. At the time, many believed tuberculosis was inherited, but Koch proved it was caused by the bacterium Mycobacterium tuberculosis. In 1882, he published his findings in The Etiology of Tuberculosis and presented them to the German Physiological Society. His work led to the creation of Koch’s postulates, which describe how to link a microorganism to a disease.

Koch continued researching tuberculosis throughout his career. He tested chemicals like arsenic and creosote as disinfectants but found them ineffective. In 1890, he tested a tuberculosis extract made from bacterial cultures and found it could kill infected tissue in guinea pigs. He announced his findings at the Tenth International Medical Congress in Berlin. In November 1890, Koch demonstrated the extract’s effectiveness in treating human patients.

Personal life

In July 1867, Koch married Emma (Emmy) Adolfine Josephine Fraatz. The couple had a daughter named Gertrude in 1868. Their marriage ended after 26 years in 1893. That same year, he married actress Hedwig Freiberg (1872–1945).

On April 9, 1910, Koch had a heart attack and never fully recovered from it. Three days after giving a lecture about his tuberculosis research at the Prussian Academy of Sciences, Koch died in Baden-Baden on May 27 at the age of 66. After his death, the Institute named its building after him as a tribute. He did not follow any religion.

Honours and legacy

Robert Koch was given the title of Knight Grand Cross in the Prussian Order of the Red Eagle on November 19, 1890. He was also chosen as a Foreign Member of the Royal Society in 1897. In 1905, he received the Nobel Prize in Physiology and Medicine for his work studying tuberculosis. In 1906, his research on tuberculosis and tropical diseases earned him the Order Pour le Merite. In 1908, he was awarded the Robert Koch Medal, which honors the most respected living physicians. Emperor Wilhelm I gave him the Order of the Crown, 100,000 marks, and appointed him as Privy Imperial Councillor, Surgeon-General of Health Service, and Fellow of the Science Senate of Kaiser Wilhelm Society.

In 1891, Koch founded the Royal Prussian Institute for Infectious Diseases in Berlin. After his death, the institute was renamed the Robert Koch Institute in his honor.

Since 1982, the World Health Organization has celebrated "World Tuberculosis Day" every March 24 to remember the day Koch discovered the bacteria that causes tuberculosis.

Koch’s name is one of 23 people from the fields of hygiene and tropical medicine featured on a frieze at the London School of Hygiene & Tropical Medicine building in Keppel Street, Bloomsbury.

A large marble statue of Koch stands in a small park called Robert Koch Platz, located just north of the Charity Hospital in the Mitte section of Berlin. His life was the subject of a 1939 German film that starred Oscar-winning actor Emil Jannings.

Koch and his connection to Paul Ehrlich, who created a method to diagnose tuberculosis, were shown in the 1940 movie Dr. Ehrlich's Magic Bullet.

On December 10, 2017, which was Koch’s birthday, Google created a special image called a Google Doodle to celebrate him.

Controversies

At their first meeting at the Seventh International Medical Congress in London in August 1881, Koch and Pasteur were friendly. However, their careers later involved scientific disagreements. The conflict began when Koch linked his discovery of the anthrax bacillus in 1876 to the cause of anthrax infections. Although his rules for proving causality were not yet written, he inferred the bacterium caused the disease. Pasteur argued that Koch’s discovery was not enough proof, but his anthrax vaccine developed in 1881 was. Koch published his findings in 1881, stating that anthrax only occurs with viable anthrax bacilli or spores and that vaccination, as claimed by Pasteur, was impossible. To test his vaccine, Pasteur sent his assistant, Louis Thuillier, to Germany to challenge Koch’s ideas. They debated publicly at the International Congress for Hygiene in Geneva in 1882, where Koch criticized Pasteur’s methods as "unreliable" and claimed they led to false conclusions. Koch later attacked Pasteur, saying, "Pasteur is not a physician, and one cannot expect him to make sound judgments about disease."

In 1890, Koch discovered tuberculin as a treatment for tuberculosis but kept the experiment secret. After public pressure, he announced the experiment and its source a year later. Clinical trials with tuberculin failed, and a report by Rudolf Virchow in 1891 showed that patients treated with tuberculin died instead of recovering. Koch later revealed that the drug was a glycerine extract of tuberculosis bacilli. A German official report in 1891 confirmed that tuberculosis was not cured by tuberculin. Koch’s reputation suffered as a result. His initial secrecy was due to his desire for financial gain and to establish his own research institute. Since 1885, Koch had aimed to leave government service and create an independent institute. After the failure of tuberculin, he was removed from the University of Berlin and forced to work at the Royal Prussian Institute for Infectious Diseases, a newly created institute, in 1891. He was not allowed to work on tuberculin or claim patent rights in future research.

Koch initially believed that human tuberculosis bacteria (Mycobacterium tuberculosis) and cattle tuberculosis bacteria (now called Mycobacterium bovis) were different. Two years later, he changed his view, claiming the two were the same. This belief influenced veterinary practices and led to laws in the United States for inspecting meat and milk. In 1898, Theobald Smith, an American veterinarian, published a study showing that tuberculosis bacteria differ in structure, growth, and disease effects. He concluded:
1. Human tuberculosis bacteria cannot infect cattle.
2. Cattle tuberculosis bacteria can infect humans because they are highly disease-causing.

By this time, evidence showed that cattle tuberculosis could spread to humans through meat and milk. Despite this, Koch claimed cattle tuberculosis was not dangerous to humans and argued that efforts to fight tuberculosis should focus only on the human bacteria. At the Third International Congress on Tuberculosis in London in 1901, Koch said, "I consider it unnecessary to take measures against this form of TB. The fight against TB must focus on the human bacillus." Joseph Lister, the congress chair, criticized Koch and explained the medical evidence showing cattle tuberculosis could harm humans.

In 1902, the Nobel Committee chose to award the Nobel Prize in Physiology or Medicine for discovering how malaria spreads. They could not decide between Ronald Ross, a British surgeon who found that malaria parasites are carried by mosquitoes, and Giovanni Battista Grassi, an Italian biologist who studied malaria parasites and their transmission. Ross discovered that mosquitoes spread malaria in 1897 and later showed bird malaria could be transmitted by mosquito bites. Grassi identified Plasmodium vivax and bird malaria parasites and proved that Plasmodium falciparum spreads between humans through mosquitoes. Surprisingly, Ross and Grassi publicly argued over the importance of their work. Robert Koch was asked to act as a neutral judge. Grassi had previously criticized Koch’s malaria research, while Ross had a good relationship with Koch. Koch supported Ross, saying Grassi did not deserve the prize, and Ross was awarded the Nobel Prize.