A son of the Warburgs
Otto Heinrich Warburg was born on October 8, 1883, in Freiburg im Breisgau, near the Swiss border. His father, the distinguished physicist Emil Warburg, came from the Altona branch of the famous Warburg family; Emil’s parents were Orthodox Jews, but he converted to Protestantism as an adult. Otto’s mother, Elisabeth Gaertner, came from a Protestant family of civil servants and soldiers in Baden. Otto was raised a Protestant.
In 1896 the family moved to Berlin, where Emil had been called to the chair of physics at the university and later became president of the Physikalisch-Technische Reichsanstalt, the national physics laboratory. Otto grew up in grand official residences where the leading scientists of imperial Germany were frequent guests. Albert Einstein was a friend of his father’s.
Chemist, physician, cavalry officer
Warburg studied chemistry under Emil Fischer, one of the giants of organic chemistry, and took his doctorate in Berlin in 1906. Fischer was a severe master: after Warburg had recrystallised a compound eight times, Fischer told him to do it twenty-five times more. Warburg never forgot the lesson, and throughout his life repeated experiments many times before publishing. He then studied medicine under Ludolf von Krehl at Heidelberg, qualifying as a doctor of medicine in 1911. Between 1908 and 1914 he worked regularly at the marine biological station in Naples, where he showed that the oxygen consumption of sea-urchin eggs rises up to sixfold upon fertilisation and that iron is essential to the process.
A lifelong horseman, Warburg served through the First World War as an officer in an elite Prussian cavalry regiment of Uhlans, was wounded, and won the Iron Cross, First Class. Toward the end of the war Einstein wrote to him, at the urging of friends, asking him to leave the army and return to science, since losing him would be a loss to the world. Warburg did, and the two became friends.
How cells breathe
In 1918 Warburg became a professor at the Kaiser Wilhelm Institute for Biology in Berlin-Dahlem, and in 1931 director of a new Kaiser Wilhelm Institute for Cell Physiology, funded by the Rockefeller Foundation. He never taught students, never sat on committees, and devoted himself entirely to the laboratory, where he designed new tools, the Warburg manometer for measuring the gas exchange of living tissue, the thin tissue-slice technique, and spectrophotometric methods for identifying enzymes inside cells.
With these tools he attacked one of the central questions of biology: how living cells use oxygen. In 1924 he identified an iron-containing “respiratory enzyme” as the agent that transfers oxygen in cell respiration. In an elegant series of experiments he showed that carbon monoxide blocks respiration by binding to this enzyme’s iron, and that bright light reverses the block; by measuring which wavelengths of light worked best, he obtained the enzyme’s absorption spectrum and showed it to be a haem compound, a relative of the pigment in blood. For “his discovery of the nature and mode of action of the respiratory enzyme” he received the 1931 Nobel Prize in Physiology or Medicine, alone, after forty-six nominations over nine years.
In the 1930s his laboratory went on to discover the “yellow enzymes” and the role of flavins and nicotinamide as the active groups of the enzymes that transfer hydrogen in living cells, completing, in the words of his Nobel biography, an account of oxidation and reduction in the living world. These discoveries became foundations of modern biochemistry, and several of his co-workers and visitors, among them Hans Krebs, later won Nobel Prizes of their own.
The Warburg effect
From the early 1920s Warburg also studied the metabolism of tumours. He found that cancer cells take up glucose greedily and break it down by fermentation into lactic acid, even when plenty of oxygen is available, unlike most healthy cells, which burn sugar completely using oxygen. This phenomenon, aerobic glycolysis, is now known as the Warburg effect.
Warburg went further and argued that cancer is caused by damage to cell respiration, which forces cells to fall back on fermentation. He defended this “prime cause” theory with absolute conviction to the end of his life, and was dismayed by the growing focus on cancer viruses and chemical carcinogens. Modern research has shown that cancer is driven primarily by mutations in oncogenes and tumour-suppressor genes, and that the metabolic shift Warburg observed is largely a consequence of those mutations rather than the original cause.
Yet his observation has proved enormously useful. The PET scans used every day in hospitals to locate tumours work by tracking a radioactive form of glucose, which cancer cells absorb in excess, the Warburg effect made visible. And since the 2000s cancer metabolism has become a major field of research once again, inspired directly by his work.
A “Mischling” in Nazi Berlin
When the Nazis came to power in 1933, the son of a converted Jew was, under the racial laws of 1935, a Halbjude, a “half-Jew” or Mischling, and Jewish scientists were being driven from German institutions. Hans Krebs, who had worked in his laboratory, was dismissed and emigrated to England. Warburg stayed. He was banned from teaching, which he never did anyway, but allowed to continue his research. In 1941 he briefly lost his post after criticising the regime, but was reinstated within weeks on an order from Hitler’s Chancellery, and Hermann Göring arranged for him to be reclassified as only one-quarter Jewish. In 1942 his application for equal status with “Aryan” Germans was granted.
Historians have suggested several reasons for this protection: the regime’s interest in cancer research, Hitler’s mother had died of cancer, Warburg’s decorated service in the First World War, and his international fame. Warburg was no Nazi: he refused to give the Nazi salute and clashed with officials. But critics have argued that his single-minded devotion to science led him to accept the persecution of Jewish colleagues and relatives without protest. He was also personally vulnerable in another way: his partner for some fifty years was Jacob Heiss, who had joined him around 1918 as an aide and later managed the institute, and Nazi laws criminalised homosexuality. In 1943 he moved his laboratory to Liebenburg to escape the bombing of Berlin.
The Rockefeller Foundation is reported to have offered to keep funding him if he emigrated, but he refused to leave. After the war he asked about moving to the United States and was turned down. A persistent story that he was chosen for a second Nobel Prize in 1944 but prevented by Hitler from accepting it is untrue, according to the Nobel Foundation, although he was considered a worthy candidate.
The eccentric of Dahlem
Warburg was famous for his arrogance as much as his brilliance. He regarded himself as a craftsman of experiment and judged colleagues harshly. Frustrated by resistance to his ideas, he liked to quote Max Planck’s observation that new scientific truths win acceptance not by convincing opponents but because the opponents eventually die. He disliked ceremonies so much that he asked for medals to be posted to him rather than leave his laboratory, though he was delighted, as an ardent anglophile, by an honorary doctorate from Oxford in 1965.
His institute was built around experiment alone: among its forty rooms there was no office and no conference room. When he left his regiment at the end of the First World War, his fellow officers joked that he was going back to “feeding sea urchins”; few would have guessed that most of his great discoveries still lay ahead. He believed that breakthroughs often came from simple, untried changes in conditions, he found the fermentation of tumour cells, for example, after raising the bicarbonate concentration of the medium twentyfold, and in 1964 he summed up his creed: a scientist must have the courage to attack the great unsolved problems of his time.
His later enthusiasms could lead him astray. Convinced of his cancer theory, he offered to testify on behalf of Josef Issels, a doctor convicted over an unproven cancer treatment. He never married. He and Heiss lived together in an elegant villa in Dahlem, and he left his entire estate to Heiss.
Last years
After the war Warburg’s institute became part of the Max Planck Society, and he continued to work, on photosynthesis, with the American biochemist Dean Burk, and on cancer, until he was eighty-six. West Germany awarded him the order Pour le Mérite for Sciences and Arts in 1952. In 1968 he broke his femur; the injury led to deep-vein thrombosis, and on August 1, 1970, he died of a pulmonary embolism in Berlin-Dahlem. He was buried in a Christian cemetery.
Legacy
Warburg’s methods and discoveries run through the textbooks of biochemistry: the respiratory enzyme, the flavin and nicotinamide coenzymes, the enzymes of fermentation, the manometer that measured them. The German Society for Biochemistry and Molecular Biology has awarded the Otto Warburg Medal, regarded as Germany’s highest honour in the field, since 1963.
His life also embodies the strange fate of Germans of Jewish descent under Nazism. Born to a father who had left Judaism and a Protestant mother, raised a Christian, he was nonetheless defined by the regime as a Jew, and survived, uniquely privileged, while others of his origin were expelled or murdered. His story, told in Ron Chernow’s history of the Warburg family and in Sam Apple’s Ravenous, remains a study in genius, ambition and moral compromise.
Sources & further reading
Otto Heinrich Warburg, Wikipedia · Otto Warburg, Biographical (NobelPrize.org) · Warburg, Otto Heinrich, Complete Dictionary of Scientific Biography via Encyclopedia.com · Researched from the sources above and checked against them. Spotted an error? Tell us.
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