Salvador Luria arrived in New York City on September 12, 1940, and soon changed his first and middle names. With the help of physicist Enrico Fermi, whom he knew from his time at the University of Rome, Luria received a Rockefeller Foundation fellowship at Columbia University. He soon met Delbrück and Hershey, and they collaborated on experiments at Cold Spring Harbor Laboratory and in Delbrück’s lab at Vanderbilt University. His famous experiment with Delbrück in 1943, known as the Luria–Delbrück experiment, demonstrated statistically that inheritance in bacteria must follow Darwinian rather than Lamarckian principles and that mutant bacteria occurring randomly can still bestow viral resistance without the virus being present. The idea that natural selection affects bacteria has profound consequences, for example, it explains how bacteria develop antibiotic resistance. From 1943 to 1950, Salvador Luria worked at Indiana University. His first graduate student was James D. Watson, who went on to discover the structure of DNA with Francis Crick. In January 1947, Luria became a naturalized citizen of the United States. In 1950, Salvador Luria moved to the University of Illinois at Urbana–Champaign. In the early 1850s, Luria and Giuseppe Bertani discovered the phenomenon of host-controlled restriction and modification of a bacterial virus: a culture of E. coli can significantly reduce the production of phages grown in other strains; however, once the phage become established in that strain, they also become restricted in their ability to grow in other strains. It was later discovered by other researchers that bacteria produce enzymes that cut viral DNA at particular sequences but not the bacteria’s own DNA, which is protected by methylation. These enzymes became known as restriction enzymes and developed into one of the main molecular tools in molecular biology. He died in Lexington, Massachusetts of a heart attack.