- Person
- Salvador Luria
- Lived
- 1912–1991
- Field
- Microbiology, genetics
- From
- Italian-American
The story
In 1943 Salvador Luria was a refugee scientist newly arrived at Indiana University. An Italian Jew, he had been pushed out of research in Italy by Mussolini’s 1938 racial laws and had fled the German invasion of France by bicycle. He was studying bacteriophages, viruses that kill bacteria, and one question kept nagging him. When a few bacteria survive a virus and their descendants become resistant, did the virus cause the change, or were resistant mutants already present by chance before the attack?
One Saturday night in Bloomington, watching a colleague play a slot machine at a faculty dance, Luria saw how to find out. A slot machine pays nothing most of the time and an occasional jackpot. Random mutations should behave the same way. If he grew many separate cultures of bacteria and then exposed each to the virus, a cause-and-effect response would give roughly the same number of resistant cells in each. Random mutation would give wild swings: most cultures with few or none, and a few jackpot cultures in which a mutation had happened early and multiplied.
Luria ran the experiment and the physicist Max Delbrück worked out the mathematics. The counts swung wildly, exactly as random mutation predicted. Their paper, published in the journal Genetics in 1943, showed that bacteria have genes that mutate spontaneously and that selection then picks out the survivors. The fluctuation test, as it is called, is still used to measure mutation rates.
The finding is the foundation for understanding drug resistance. Antibiotics do not teach bacteria to resist; among billions of cells, a few already carry chance mutations, and the drug clears away their rivals. That logic explains why unnecessary antibiotic use breeds resistant germs and why diseases such as tuberculosis and HIV are treated with several drugs at once, so that no single chance mutant can survive them all. Luria shared the 1969 Nobel Prize in Physiology or Medicine with Delbrück and Alfred Hershey.
Why it matters
Luria’s proof that resistance comes from random mutation plus selection underpins how doctors use antibiotics and combination therapies to keep drugs working.
About Salvador Luria
Italian Jewish refugee who proved that bacteria mutate at random, the key to understanding drug resistance, helped found molecular biology and trained James Watson.
Sources
- Luria, Salvador Edward (Complete Dictionary of Scientific Biography) Encyclopedia.com
- Historical Highlight: The Luria-Delbrück Fluctuation Test Pathogens and Immunity (PubMed Central)
- The Salvador E. Luria Papers: Biographical Overview US National Library of Medicine
Another act 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.