A Jewish family in Turin
Salvatore Luria was born in Turin, in northern Italy, on August 13, 1912, the second son of David Luria, an accountant, and Esther Sacerdote. The family belonged to Turin’s old Italian Jewish community. His school years coincided with the rise of Mussolini’s Fascism, and several of his teachers, men who quietly resisted the regime, left a deep mark on him. At the Liceo Massimo d’Azeglio he studied philosophy and literature with Augusto Monti, a well-known anti-Fascist.
Partly to please his parents, he studied medicine at the University of Turin. He worked in the histology laboratory of Giuseppe Levi, a demanding teacher and committed anti-Fascist, whose students in those years included two other future Nobel laureates, Rita Levi-Montalcini and Renato Dulbecco. Luria graduated with the highest honours in 1935, but he never felt much enthusiasm for practising medicine. A physicist friend, Ugo Fano, had already got him interested in physics.
Exile
After compulsory army service as a medical officer in 1936 and 1937, Luria went to Rome to study radiology and, at Fano’s urging, physics, in the circle of Enrico Fermi. There he read the theories of the German physicist Max Delbrück, who thought the gene could be studied as a physical molecule, and he began working with bacteriophages, the viruses that infect bacteria. They seemed to him the perfect tool for testing those ideas.
In 1938 he won a fellowship to work in the United States. Then Mussolini’s racial laws barred Jews from research fellowships and ended his prospects in Italy. He left for Paris, where he worked at the Institute of Radium. When the German army invaded France in June 1940, Luria fled south by bicycle to Marseille, obtained an American immigration visa, and travelled through Lisbon to New York, where he landed on September 12, 1940. He soon changed his name to Salvador Edward Luria.
The phage group
With help from Fermi, Luria received a Rockefeller Foundation fellowship at Columbia University. In December 1940 he finally met Delbrück, and the two began a partnership, joined by the chemist Alfred Hershey, that came to be known as the phage group. Working summers at Cold Spring Harbor Laboratory on Long Island, they turned bacteriophages into the simplest possible system for asking how genes copy themselves and change. The informal network of scientists they trained and inspired is often credited with founding molecular biology.
In 1943 Luria moved to Indiana University. His first graduate student there was a young man from Chicago named James Watson, who went on to discover the double-helix structure of DNA with Francis Crick. Renato Dulbecco, his old friend from Turin, joined the laboratory too.
Luria’s laboratory also produced tools that biologists still use every day. In 1947, with the French physicist Raymond Latarjet, he published a careful analysis of how ultraviolet light damages phages at different stages of infection, work that later helped reveal the DNA repair systems carried by viruses. And a nutrient medium developed in his group by his colleague Giuseppe Bertani, lysogeny broth, became so closely linked with his name that generations of students have known it as Luria broth. It remains one of the most common recipes for growing bacteria in laboratories worldwide.
The slot machine and the jackpot
The question Luria was chewing on was an old one. When bacteria become resistant to a virus that should kill them, do they change in response to the attack, or were a few resistant mutants already there, waiting to be selected? Many bacteriologists assumed the first. One Saturday night in Bloomington in early 1943, a few weeks after arriving at Indiana, Luria was at a faculty dance watching a colleague play a slot machine. Most pulls paid nothing, a few paid a little, and once in a while one paid a jackpot. He realised that random mutations would behave the same way.
If resistance were triggered by the virus, many separate bacterial cultures exposed to it should all contain roughly similar numbers of resistant cells. If mutations happened at random beforehand, the numbers would vary wildly: most cultures would have few or none, but a culture in which a mutation had happened early would be packed with resistant descendants, a jackpot. Luria ran the experiment, Delbrück worked out the mathematics, and the results matched random mutation. Their 1943 paper in the journal Genetics showed that bacteria have genes that mutate spontaneously, just like those of plants and animals, and that natural selection then picks the survivors. The method, the fluctuation test, is still used to measure mutation rates.
Why it matters: resistance and the tools of biotechnology
The fluctuation test explains one of the great medical problems of our time. Bacteria do not learn to resist antibiotics; among billions of cells, a few already carry chance mutations that let them survive, and the drug kills their competitors and lets them take over. That understanding shapes how medicine fights resistance: why doctors warn against unnecessary antibiotics, why tuberculosis and HIV are treated with several drugs at once so that no single mutant can escape all of them, and why cancer specialists apply the same reasoning to tumours that become resistant to chemotherapy. Luria himself directed a government research project on bacterial resistance to antibiotics at Cold Spring Harbor in 1945.
His second major discovery reached even further. At the University of Illinois in the early 1950s, Luria and his colleagues noticed that a phage grown in one strain of bacteria often failed to grow in another, a phenomenon called host-controlled restriction and modification. Other researchers later traced it to bacterial enzymes that cut foreign DNA at particular sequences. These restriction enzymes became the scissors of genetic engineering. They made recombinant DNA possible in the 1970s, and with it the bacteria and yeast that now produce human insulin, growth hormone, vaccines and many other medicines.
Builder of a cancer centre
In 1959 Luria moved to the Massachusetts Institute of Technology to head its new microbiology programme, and in 1964 he became Sedgwick Professor of Biology. He shared the 1969 Nobel Prize in Physiology or Medicine with Delbrück and Hershey for their discoveries on how viruses replicate and on their genetic structure. In 1972 MIT asked him to build and lead a new Center for Cancer Research, which opened in 1973. He directed it until 1985, and the scientists he recruited included David Baltimore, Susumu Tonegawa, Phillip Sharp and H. Robert Horvitz, all future Nobel laureates. The centre is the forerunner of today’s Koch Institute for Integrative Cancer Research at MIT.
Luria was also a gifted writer and teacher. His textbook General Virology (1953) trained a generation, and his book for general readers, Life: The Unfinished Experiment, won the National Book Award in 1974. In 1984 he published an autobiography whose title, A Slot Machine, a Broken Test Tube, recalled the two moments of chance that had shaped his science.
A scientist with a conscience
Luria believed that scientists had a duty to speak out against injustice and against irresponsible uses of technology. He opposed loyalty oaths in the McCarthy years, supported labour unions and civil rights, signed Linus Pauling’s 1957 appeal against nuclear weapons testing and opposed the Vietnam War. In the early 1950s the FBI investigated him and the State Department refused him a passport, and in 1969 his name turned up on a blacklist that briefly kept him from receiving National Institutes of Health grants. He announced that he would give part of his Nobel money to the peace movement. He also criticised Israel’s 1982 invasion of Lebanon. In the 1970s debate over genetic engineering, he took a middle position, favouring sensible oversight rather than either a ban or no rules at all.
Jewish identity
Luria was born into Turin’s Jewish community, and the defining break of his life came because of it: Fascist Italy’s 1938 racial laws shut him out of research, and the Nazi invasion of France turned him into a refugee for a second time. He was one of a remarkable group of Italian Jewish scientists, among them Rita Levi-Montalcini and the physicist Emilio Segrè, whose careers were upended by those laws and who later did much of their greatest work in the United States. He is included in the Encyclopaedia Judaica and in lists of Jewish Nobel laureates.
Family and legacy
In 1945 Luria married Zella Hurwitz, a psychologist who later became a professor at Tufts University; their only child, Daniel, was born in 1949 and went on to study economics. Colleagues remembered Luria as warm and witty, with interests far beyond the laboratory: on a sabbatical in France in the 1960s he studied sculpture, and at MIT he taught a course on world literature. He became a United States citizen in 1947 and received the National Medal of Science in 1991. He died at his home in Lexington, Massachusetts, on February 6, 1991, at the age of 78.
His legacy runs through modern biology and medicine. The idea that resistance comes from random mutation plus selection guides how doctors use antibiotics and cancer drugs. The restriction enzymes that grew out of his phage experiments made biotechnology possible. And the people he trained and recruited, from Watson to the founders of MIT’s cancer research, carried his habits of rigour and curiosity into the next half-century of science.
Sources & further reading
The Salvador E. Luria Papers: Biographical Overview, Profiles in Science, US National Library of Medicine · Salvador E. Luria, Biographical, NobelPrize.org · Luria, Salvador Edward, Encyclopedia.com (Complete Dictionary of Scientific Biography; Encyclopaedia Judaica) · Historical Highlight: The Luria-Delbrück Fluctuation Test, Pathogens and Immunity, 2024 · Salvador Luria, Wikipedia · Researched from the sources above and checked against them. Spotted an error? Tell us.
A life of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.