LURIA, SALVADOR EDWARD (SALVATORE)

(b. Turin, Italy, 13 August 1912; d. Lexington, Massachusetts, 6 February 1991),

virology, bacterial genetics, molecular biology, cancer research.

Luria was one of the central figures in the development of twentieth-century life sciences. His 1940s research on bacteriophage and its bacterial hosts laid the groundwork for the emergence of bacterial genetics and virology as independent disciplines. He shared the 1969 Nobel Prize in Physiology or Medicine with his longtime collaborators Max Delbrück and Alfred Hershey for “discoveries concerning virus replication and genetics and … the importance of your contributions to the biological and medical sciences.” Luria also played a role in the establishment of molecular biology, as his first graduate student was James D. Watson. His career trajectory from basic research on microorganisms to cancer research parallels the development of the life sciences in the postwar era. An immigrant to the United States, Luria was a passionate participant in American politics who publicly articulated his scientific and political ideals in the context of the Cold War.

Origins and Early Scientific Training . Salvatore Luria was born in the Northern Italian city of Turin, the second son of a lower-middle-class Jewish family. He was educated at Turin’s elite institutions, the Liceo Massimo d’Azeglio and the medical school of the University of Turin, at a time when the city was a seat of antifascist activity. At the Liceo, he studied philosophy and literature with Augusto Monti, a famous antifascist intellectual. In medical school, Luria worked for several years in the histology laboratory of the talented researcher Giuseppe Levi, who was also a committed antifascist. Although he was not politically active as a youth, these mentors impressed him with their dedication to democratic and rational ideals. Luria graduated from medical school with highest honors in 1935.

Luria was not interested in practicing medicine. During medical school, he became interested in the ways in which modern physics could be applied to problems in biology and genetics. After completing his required year of army service as a medical officer, he arranged to spend 1937–1938 studying with the physicist Enrico Fermi in Rome. During his year in Rome, he first encountered the work of physicist-turned-biologist Max Delbrück and began experimenting with bacteriophage, the viruses that attack bacteria. When Benito Mussolini passed a set of race laws that restricted the participation of Jews in public life in July 1938, Luria was prevented from pursuing a career in science in Italy. Luria took the opportunity to leave both Italy and medicine behind, and he moved to France to pursue virus research at the Institut Pasteur. He collaborated with Fernand Holweck and Eugène Wollman, and learned their statistical techniques for analyzing virus growth. When the Nazis invaded France in the spring of 1940, Luria fled again, this time to the United States via Portugal. He arrived in New York City on 12 September 1940.

Bacteriophage Research . As soon as he reached the United States, Luria began the process of becoming an American scientist. He secured funding from the Rockefeller Foundation and the Dazian Medical Foundation for Medical Research and was appointed to a temporary position in the Bacteriology Department at Columbia University. On his application for citizenship, Luria changed his first name from the Italian “Salvatore” to the Spanish spelling “Salvador” and added the English middle name “Edward.” He first met Delbrück in December 1940, and the two immediately began to collaborate.

Despite their geographic separation, Luria and Delbrück had an instant intellectual closeness. They arranged to spend the summer of 1941 at Cold Spring Harbor Laboratories, in New York, investigating the genetic and biochemical properties of bacteriophage and its host Escherichia coli. Their first joint publication described the curious way that two different strains of virus interfere with each other’s growth when both infect a colony of bacteria. They soon began to consider the implication of virus research for questions of resistance and evolutionary adaptation. Luria and Delbrück also collaborated with Thomas Anderson at the RCA Laboratories, taking some of the first electron micrograph images of bacteriophage.

During that summer at Cold Spring Harbor, Luria first met Milislav Demerec and Hermann Muller, both of whom were instrumental in helping him win a Guggenheim fellowship in 1942 and eventually to secure a permanent academic position. In January 1943, Luria moved to Bloomington, Indiana, to begin teaching in the Botany and Bacteriology Department at Indiana University. Luria and Delbrück returned to Cold Spring Harbor nearly every summer during the 1940s and 1950s to collaborate and to teach.

Luria flourished at Indiana professionally and personally. He formed close friendships with his colleagues including Leland McClung, Muller, and Tracy Sonneborn and began to train graduate students and postdoctoral researchers. His first advisee was James Dewey Watson, who soon became part of the larger community of phage researchers. In 1947 Luria invited his Italian medical school colleague Renato Dulbecco to work in his laboratory. Later, he was joined by Giuseppe Bertani, who worked on lysogeny and developed the standard culture for growing bacteria. Bertani referred to his “lysogeny broth” medium as “LB” in a 1951 paper, and the abbreviation soon became known as “Luria broth.” In 1945, Luria married Zella Hurwitz, the only female graduate student in the Department of Psychology. Their son Daniel was born in 1948.

Bacterial Genetics . A few weeks after he arrived in Bloomington, Luria got an idea for an experiment one Saturday night while watching a colleague play a slot machine at a faculty dance. Because he and Delbrück had first worked with bacterial resistance to phage, Luria had considered the problem of how that resistance arose. He considered two possible hypotheses: that the resistance was somehow triggered by the presence of bacteriophage, or that some of the bacteria were already resistant as a result of random genetic mutations. However, it was unclear how to test these possibilities experimentally.

As he teased his friend about gambling, Luria realized that mutations in bacteria could be considered analogous to jackpots. He saw that jackpots in an unprogrammed slot machine are a series of random events that could be described with a Poisson distribution of rare independent events. Luria hypothesized that if bacterial resistance to bacteriophage was the result of spontaneous random mutations, then it would appear in a random distribution of “jackpots” in a series of cultures. Some cultures could have many resistant colonies while others could have none. If, on the other hand, resistance was acquired as a result of contact with phage, resistant colonies would be evenly distributed across all cultures. In either case, the average number of resistant colonies across all cultures could be the same, but the distribution would indicate whether the cause was spontaneous or not.

Luria ran the experiment with α, a virulent strain of phage, and as he anticipated, he found several jackpots randomly distributed among the plates. Luria was fortunate to have chosen virulent phage. If he had used a temperate strain, he would have seen that the presence of phage did induce resistance, and he would have concluded that it was acquired rather than hereditary. Excited by his results, Luria consulted with Delbrück, who noted that the experiment also provided a way to determine mutation rates with greater precision than had been possible before.

This experiment, known as the fluctuation test, was published in Genetics in 1943. The implications of Luria and Delbrück’s work went far beyond the handful of researchers interested in phage. As Luria and others have pointed out, the 1943 paper dealt a blow to the neo-Lamarckian view that viruses somehow induced mutations in bacteria. In a 1947 review, Luria noted that bacteriology had been “one of the last strongholds of Lamarckism,” because of the difficulty in providing direct evidence for the existence of both Mendelian traits and the characteristic Darwinian criteria of random change (p. 1). The fluctuation test marked the beginning of Luria’s appreciation for the evolutionary implications of his genetics research, and his interest in larger biological questions was evident in his publications through the 1950s. Gunther Stent’s classic textbook Molecular Genetics equates this publication with Gregor Mendel’s 1865 paper on “Versuche über Pflanzenhybriden” (Experiments on plant hybrids), and historian Thomas Brock identifies it as the founding document of modern bacterial genetics.

Luria had a small role in the Western scientific campaign to discredit Trofim Lysenko’s Lamarckian genetics program in the Soviet Union. In 1946, Luria drafted a letter to the British biologist J. B. S. (John Burdon Sanderson) Haldane asking him to publish a critique of Lysenko’s book Heredity and Its Variability. Muller, Theodosius Dobzhansky, Leslie Dunn, Curt Stern, and Luria signed the letter, which enraged Haldane, a committed Communist, so much that he not only refused to write the review, but returned the original letter to Muller. Later in the 1940s and early 1950s, Luria served as a member of the Genetics Society of America’s Committee to Aid Geneticists Abroad and he ran unsuccessfully for a spot on the society’s Committee to Combat Anti-genetic Propaganda.

Luria’s early experiments with bacteriophage earned him recognition from the biological community and helped establish viruses as useful research organisms. In 1945 he won a grant from the American Cancer Society’s Committee on Growth, which was renewed for over twenty years. Luria delivered the first Slotin Memorial Lecture in 1948 and gave the 1950 Jesup Lectures at Columbia University on “The Reproduction of Viruses.” Several top biology and bacteriology departments tried to recruit Luria and in 1950 he accepted an offer from the University of Illinois at Urbana-Champaign to join their Department of Bacteriology.

Restriction-Modification . Luria continued his innovative virus research in Illinois. His second key finding—host-induced modifications of viruses—was the result of a laboratory accident rather than a planned experiment. In the spring of 1952, Luria and his graduate student Mary Human reported a “novel situation” that they had observed. A test tube full of phage-sensitive E. coli culture broke, so Luria substituted a different bacterium, Shigella dysenteriae, and observed a surprising phenomenon. After exposure to Shigella, the viruses would not grow in E. coli. Some bacterial mutants had temporarily modified their viral invaders so that they could not reproduce in certain bacterial hosts.

In a series of experiments with different phages and a range of E. coli and Shigella hosts, some of the phages seemed to disappear, only to reappear when cultured with different bacteria. Luria and Human observed that one generation later, the phages once again reproduced in the original hosts. They concluded that whatever had caused the modification in the viruses was not a mutation, which would have caused permanent genetic change, or even evidence of the “peculiar plasticity of virus heredity” (Luria, 1953a, p. 237). Rather, they had found a new type of genetic variation, which they labeled “host-induced” (Luria and Human, 1952, p. 557) and later became known as the restriction-modification phenomenon.

For several years, restriction-modification was a laboratory curiosity for virologists and bacterial geneticists. In the 1960s, however, other researchers discovered that the temporary changes were the result of bacterial restriction enzymes that degraded viral DNA as a defense mechanism. Restriction enzymes, which recognize and target short strands of DNA, were key for the development of recombinant DNA technology in the late 1960s and early 1970s, which in turn is the basis for genetic engineering and other types of genetic manipulation. Luria later acknowledged that his role in the history of recombinant DNA technology was “accidental” and “serendipitous” (Luria, 1983, p. 57); this episode provides further evidence of his far-reaching influence on modern biology.

Virology . The 1950s were a critical decade in the history of virology. Luria was a strong force in the establishment of virology as an independent discipline and he published several important pieces on the utility of viruses as a fundamental biological unit. In “Bacteriophage: An Essay on Virus Reproduction” published in May 1950 in Science, he made a clear argument for virology as the key discipline that would help biologists reach their “ultimate goal, the identification of the elementary ‘replicating units’ of biological material and the clarification of their mode of reproduction” (p. 511). This essay, also published as a core reading for a California Institute of Technology conference on viruses in March 1950, gives an operational definition of viruses that emphasizes their research functions rather than their disease-causing features. A virus is “an exogenous submicroscopic unit capable of

multiplication only inside specific living cells” (p. 507). It describes the relationship between viruses and hosts as “parasitism at the genetic level,” and argues that understanding the biochemical and genetic features of that relationship would lead directly to a detailed description of all biological replication (pp. 510–511).

Nearly three years later, in April 1953, Luria’s student James Watson and his Cambridge colleague Francis Crick announced that they had discovered the double helical structure of DNA, the molecule that constitutes genetic material. Watson, Stent, and John Cairns bound the early history of molecular biology with bacteriophage in their festschrift for Delbrück’s sixtieth birthday, the classic Phage and the Origins of Molecular Biology. Although historians have demonstrated that many disciplinary strands came together to form molecular biology, the bacteriophage experiments performed by Seymour Cohen, Alfred Hershey, and Martha Chase provided critical evidence that DNA is the physical location of genetic material.

General Virology . The year 1953 was a turning point in the independent disciplinary history of virology as well. That year, Luria published General Virology, the first comprehensive textbook in the field. The text emerged from Luria’s teaching experience in Indiana. In the preface, he recalled how in 1946 he began planning a new course in virology, one that was not “a watered-down course in virus diseases,” but rather “a new type of course, in which virology would be presented as a biological science, like botany, zoology, or general bacteriology” (p. ix). His approach for the course and for the textbook accepted the ambiguities inherent in nonmedical virus research, and made it “a central concept, that of the dual nature of viruses as inert particles on the one hand, and as operating constituents of functional cells on the other hand” (p. x). Physics, chemistry, biochemistry, and cell physiology were thus integrated into the study of virus properties and behavior, while pathology was relegated to a supporting role.

In the textbook, Luria argued that virology should be considered an integrative and interpretive science, rather than a taxonomic one. By defining virology as the science concerned with the genetic and chemical properties and functions of viruses, he emphasized methodology over taxonomy. He was unequivocal about the relevance of virus research to fundamental biological questions. Some biologists felt that viruses should not be considered living, since they could not reproduce independently. However, Luria felt that the genetic dependence of viruses “makes them invaluable to the biologist, whom they present with the unique opportunity of observing in isolation the active determinants of biological specificity, which are truly the stuff of which all life is made” (p. 363). Luria took pains to establish virology as a basic science, but from the very start, his research had implications for the applied field of cancer research.

Viruses and Cancer . In 1959 the American Cancer Society organized a three-day meeting to discuss “The Possible Role of Viruses in Cancer” and to assess the state of the field. The conference brought together a diverse group of the most prominent researchers in the areas of animal, plant, and bacterial viruses, including Peyton Rous, Wendell Stanley, Renato Dulbecco, François Jacob, and André Lwoff. Luria was invited to give the keynote orienting address for the meeting and the papers were published in Cancer Research in 1960.

In “Viruses, Cancer Cells, and the Genetic Concept of Virus Infection,” Luria reviewed basic virology findings that were relevant to cellular function, which is a crucial element in the understanding of cancer as the result of abnormal cell growth and control. He noted that viruses could be implicated in the development of cancer either as the cause of somatic mutations or as a direct infection of a tumor-causing agent. In both cases, viruses could be seen as causing a type of cellular mutation since the “entry of the viral genome is a genetic change” (p. 679) and viral tumors thus would be examples of “infective heredity at the cellular level” (p. 680). While this view of the relationship between cancer and viruses was not universally accepted, it was a strong approach taken by many researchers for the next several decades.

1950s: Early Political Activity . Because of his left-leaning political affiliations, Luria attracted the attention of the Federal Bureau of Investigation (FBI) in 1950. A two-year investigation yielded no evidence of Communist or other subversive activity, but Luria was nevertheless denied a passport in 1952. He was scheduled to give a lecture at the Society for General Microbiology meeting in Oxford, England, and to visit his mother in Italy, but he was told by Ruth Shipley, chief of the passport division of the State Department, that his “proposed travel would not be in the best interest of the United States” (letter from Shipley to S.E.L., 25 January 1952, State Department correspondence folder, Luria papers, American Philosophical Society). Despite appeals by Luria and the president of the University of Illinois, Luria was not granted permission to leave the United States. James Watson reported on the latest phage research in Luria’s stead, and Luria was not granted a passport until 1959.

This treatment did not deter him, however, and Luria increased his political activities during the 1950s. He helped organize protests against Illinois state laws requiring university professors and other employees to sign loyalty oaths, and was active in local labor and desegregation campaigns. In his capacity as a vice president of the American Association for the Advancement of Science, he participated in a lively debate about the appropriateness of holding a national scientific meeting in racially segregated Atlanta. Luria was one of the first signers of Linus Pauling’s 1957 “Appeal by American Scientists to the Government and Peoples of the World” to ban nuclear weapons.

Move to Boston . In 1959 the Luria family moved to Boston. Because rules against nepotism barred two members of the same family from teaching at the University of Illinois, Zella Luria could not find work as a psychology professor in Urbana. She was offered a position at Tufts University and Salvador accepted an invitation from the Massachusetts Institute of Technology (MIT) to join their Department of Biology. With the exception of the time he spent at the Pasteur Institute in 1963 as a Guggenheim Fellow, Luria remained at MIT for the rest of his career.

At MIT, Luria was instrumental in transforming their Department of Biology into a world-class research community. Along with fellow faculty members Boris Magasanik, Alexander Rich, and Irwin Sizer, he recruited top researchers and graduate students, including David Baltimore. He helped shift the department’s pedagogical focus toward genetics and microbiology and in the process increased undergraduate enrollment significantly. Luria was elected to the National Academy of Sciences in 1960. In 1966, he was named the first William Thompson Sedgwick Professor of Biology and in 1970 he became an institute professor. Luria’s status as an authority on viruses and cancer helped MIT win one of the first federal grants for basic cancer research as part of the “war on cancer.” Luria served as the director of MIT’s Center for Cancer Research from 1972 until he retired in 1985.

Protesting the Vietnam War . The height of Luria’s political involvement came in the 1960s and 1970s. He was one of the founding members of the Boston Area Faculty Group on Public Issues, a cohort of academics who sponsored advertisements and wrote editorials on political issues. Their main focus was on protesting the Vietnam War in a series of advertisements in the New York Times and other national publications. The most dramatic advertisement appeared in January 1967. Surrounding the words “Mr. President, Stop the Bombing” were the names of more than two thousand academics from around the United States.

Luria’s leadership role in the scientific community gave him the opportunity to mobilize biologists against the Vietnam War. As the president of the American Society for Microbiology in 1968, he announced that the society would terminate its advisory relationship with the U.S. Army’s Biological Laboratory at Fort Detrick, Maryland. In a widely publicized address on “The Microbiolo-gist and His Times,” Luria articulated a vision of “a society in which science will flourish, both as a liberating intellectual activity and as the source of a beneficial technology” (1968, p. 403).

Public Figure . Luria’s public roles converged in one dramatic weekend in October 1969. He helped organize the Vietnam War Moratorium in Boston on 15 October. The next day, his Nobel Prize was announced, and Luria declared that he would donate part of his prize money to the peace movement. On 20 October, Luria again made headlines when his name was found on a list of scientists who had been blacklisted from serving on advisory committees at the National Institutes of Health, presumably because of their political views.

Late in his career, Luria had many opportunities to argue for the value of science in a democratic society. He testified before Senate and Congressional committees on science policy, and was one of the first fellows of the Salk Institute in La Jolla, California. He wrote articles, textbooks, curricula, and a popular science book. In Life: The Unfinished Experiment (1973), he explained evolution, genetics, and molecular biology to a general audience while critiquing sociobiology and other examples of biological determinism. This book was a critical success and won the National Book Award in 1974. Luria continued to publish essays and op-eds on scientific and political issues until his death from cancer on 6 February 1991.

BIBLIOGRAPHY

A complete bibliography is available in Luria’s papers, deposited at the American Philosophical Society Library in Philadelphia. A list of many of his scientific publications since 1955 can be retrieved through the Web of Science database. Other archival sources include the collections at the American Society for Microbiology, the Cold Spring Harbor Laboratory, Indiana University, the Massachusetts Institute of Technology, the Rockefeller Archive Center, and the University of Illinois, Urbana-Champaign. Luria’s FBI files were obtained by this author through a Freedom of Information Act request in 1999.

WORKS BY LURIA

With Thomas F. Anderson. “The Identification and Characterization of Bacteriophages with the Electron Microscope.” Proceedings of the National Academy of Sciences of the United States of America 28 (1942): 127–130.

With Max Delbrück. “Interference between Bacterial Viruses: I. Interference between Two Bacterial Viruses Acting upon the Same Host, and the Mechanism of Virus Growth.” Archives of Biochemistry 1 (1942): 111–141.

With Max Delbrück. “Interference between Inactivated Bacterial Virus and Active Virus of the Same Strain and of a Different Strain.” Archives of Biochemistry 1 (1942): 207–218.

With Max Delbrück. “Mutations of Bacteria from Virus Sensitivity to Virus Resistance.” Genetics 28 (1943): 491–511.

With Max Delbrück and Thomas F. Anderson. “Electron Microscope Studies of Bacterial Viruses.” Journal of Bacteriology 46 (1943): 57–76.

“Recent Advances in Bacterial Genetics.” Bacteriological Reviews 11 (1947): 1–40.

With Renato Dulbecco. “Genetic Recombinations Leading to Production of Active Bacteriophage from Ultraviolet Inactivated Bacteriophage Particles.” Genetics 34 (1949): 93–125.

“Bacteriophage: An Essay on Virus Reproduction.” Science 111 (12 May 1950): 507–511. Reprinted in Viruses 1950, edited by Max Delbrück. Pasadena: Division of Biology of the California Institute of Technology, 1950.

With Mary L. Human. “A Nonhereditary, Host-Induced Variation of Bacterial Viruses.” Journal of Bacteriology 64 (1952): 557–569.

General Virology. New York: John Wiley and Sons, 1953a. “Host-Induced Modifications of Viruses.” In Viruses. Cold Spring Harbor Symposia on Quantitative Biology 18. Cold Spring Harbor, NY: Cold Spring Harbor Press, 1953b.

“Viruses, Cancer Cells, and the Genetic Concept of Virus Infection.” Cancer Research 20 (June 1960): 677–688.

“Mutations of Bacteria and of Bacteriophage.” In Phage and the Origins of Molecular Biology, edited by John Cairns, Gunther Stent, and James D. Watson. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press, 1966. Revised and expanded ed., 1992.

With James E. Darnell Jr. General Virology. 2nd ed. New York: John Wiley and Sons, 1967.

“The Microbiologist and His Times.” Bacteriological Reviews 32 (December 1968): 401–403.

Life: The Unfinished Experiment. New York: Charles Scribner’s Sons, 1973.

36 Lectures in Biology. Cambridge, MA: MIT Press, 1975.

“Phage; Colicins and Macroregulatory Phenomena.” In Nobel Lectures in Molecular Biology, 1933–1975, edited by David Baltimore. New York: Elsevier, 1977.

With James E. Darnell Jr., David Baltimore, and Allan Campbell. General Virology. 3rd ed. New York: John Wiley and Sons, 1978.

With Stephen Jay Gould and Sam Singer. A View of Life. Menlo Park, CA: Benjamin/Cummings, 1981.

“Ethical and Institutional Aspects of Recombinant DNA Technology.” In Recombinant DNA Research and the Human Prospect, edited by Earl D. Hanson. Washington, DC: American Chemical Society, 1983.

A Slot Machine, a Broken Test Tube: An Autobiography. New York: Harper and Row, 1984.

OTHER SOURCES

Abir-Am, Pnina G. “Entre mémoire collective et histoire en biologie moléculaire: les premiers rites commémoratifs pour les groupes fondateurs.” In La mise en mémoire de la science: Pour une ethnographie historique des rites commémoratifs, edited by Pnina G. Abir-Am. Amsterdam: Overseas Publishers Association, 1998.

Bertani, Giuseppe. “Lysogeny at Mid-Twentieth Century: P1, P2, and Other Experimental Systems.” Journal of Bacteriology 186 (2004): 595–600.

Brock, Thomas D. The Emergence of Bacterial Genetics. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press, 1990.

Cairns, John, Gunther Stent, and James D. Watson, eds. Phage and the Origins of Molecular Biology. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press, 1966. Revised and expanded ed., 1992. This volume, published in honor of Max Delbrück’s sixtieth birthday, was the first attempt by molecular biologists to write their own history.

Fischer, Ernst Peter, and Carol Lipson. Thinking about Science: Max Delbrück and the Origins of Molecular Biology. New York: W. W. Norton, 1988.

Judson, Horace Freeland. The Eighth Day of Creation: Makers of the Revolution in Biology. New York: Simon & Schuster, 1979. One of the standard historical accounts of the emergence of molecular biology, based on extensive interviews with the participants.

Kay, Lily E. “Conceptual Models and Analytical Tools: The Biology of Physicist Max Delbruck.” Journal of the History of Biology 18, no. 2 (Summer 1985): 207–247.

———. The Molecular Vision of Life: Caltech, the Rockefeller Foundation and the Rise of the New Biology. Oxford: Oxford University Press, 1993.

———. Who Wrote the Book of Life: A History of the Genetic Code. Stanford, CA: Stanford University Press, 2000.

Krementsov, Nikolai. “A ‘Second Front’ in Soviet Genetics: The International Dimension of the Lysenko Controversy, 1944–47.” Journal of the History of Biology 29 (1996): 229–250.

Lysenko, Trofim Denisovich. Heredity and Its Variability. Translated from the Russian by Theodosius Dobzhansky. New York: King’s Crown Press, 1945.

Mendel, Gregor. “Versuche über Pflanzenhybriden.” Verhandlungen des Naturforschenden Vereins in Brünn 4 (1866): 3–57. Read at 1865 meeting.

Morange, Michel. A History of Molecular Biology. Cambridge, MA: Harvard University Press, 1998.

“Nobel Prize in Physiology or Medicine, 1969.” Nobel Prize Web site. Available from http://nobelprize.org/nobel_prizes/medicine/.

Olby, Robert. The Path to the Double Helix: The Discovery of DNA. Seattle: University of Washington Press, 1974. 2nd ed., 1994. Another standard historical account, focusing more on the technological and experimental roots of the discovery of DNA.

Rasmussen, Nicolas. Picture Control: The Electron Microscope and the Transformation of Biology in America, 1940–1960. Stanford, CA: Stanford University Press, 1997.

Selya, Rena. “Salvador Luria’s Unfinished Experiment: The Public Life of a Biologist in Cold War America.” PhD diss., Harvard University, 2002.

Stent, Gunther S. Molecular Genetics: An Introductory Narrative. San Francisco: W. H. Freeman, 1970.

Summers, William C. “How Bacteriophage Came to Be Used by the Phage Group.” Journal of the History of Biology 26 (1993): 255–267.

Watson, James D. “Growing up in the Phage Group.” In Phage and the Origins of Molecular Biology, edited by John Cairns, Gunther Stent, and James D. Watson. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press, 1966. Revised and expanded ed., 1992.

———. The Double Helix: A Personal Account of the Discovery of the Structure of DNA. Norton Critical Edition, edited by Gunther Stent. New York: W. W. Norton, 1980. James Watson was Luria’s first graduate student. These two works reflect Watson’s intense interest in shaping how the history of molecular biology is written and presented to the public.

Rena Selya

Luria, Salvador Edward

(b. 13 August 1912 in Turin, Italy; d. 6 February 1991 in Lexington, Massachusetts), micro-biologist whose research on the genetics of viruses and bacteria earned him the Nobel Prize in 1969.

Born Salvatore Luria and nicknamed “Salva,” Luria belonged to a middle-class branch of an old and proud Jewish family. His father, David Luria, an accountant, and his well-read mother, Esther Sacerdote, a homemaker, encouraged a refined intellectualism. Salva’s older brother was an early role model. As Fascism developed in Italy, Luria responded to the liberal socialism of a rebellious high school literature teacher. His lifelong friend, Ugo Fano, inspired an interest in physics and pure science. Not a passionate student, Salva chose medical school and graduated from the University of Turin in 1935, unenthusiastic about treating patients.

Luria served his internship in the medical histology laboratory of Giuseppe Levi, where he learned experimental techniques and maintained (as he would throughout life) an active interest in literature. Attempting to combine the strengths of medicine and physics, Luria then joined a radiology laboratory. During this time he served for eighteen months (and he reported, ineptly) in the Italian army.

Looking to prepare for a career in science, Luria affiliated in 1937 as a radiologist with the physics laboratory of Enrico Fermi at the University of Rome. During this period Luria was exposed to the German physicist Max Delbruück’s ideas regarding the molecular nature of the gene. The bacteriologist Gio Rita introduced Luria to bacteriophage viruses and to related laboratory techniques. Just when Luria won an Italian government fellowship to travel to Delbrück’s laboratory in Berkeley, California, the Fascist racial laws (which among other laws, excluded Jews from any government position and most other positions of responsibility) were passed and Luria’s fellowship disappeared.

While his family stayed, suffered, and survived the Fascist era and the war, Luria was eager to cut his ties to the past and create a new future. He emigrated first to Paris in 1938 and worked at the Institute of Radium on the effects of radiation on bacteriophage. Paris provided ample opportunity for him to exercise his interest in radical socialist politics. After enduring the fall of Paris to the German army on 14 May 1940, Luria departed by bicycle, making his way toward Lisbon with the help of expatriate Italians. Having obtained a U.S. visa in Marseilles, he entered New York Harbor on 12 September 1940 with $52 and the clothes on his back.

Enrico Fermi, then at Columbia University, helped Luria obtain a Rockefeller Foundation fellowship to continue his research at Columbia’s College of Physicians and Surgeons. Luria applied immediately for citizenship, using the opportunity to adopt the Spanish variant of his name and transposing the truncated “e” to a new middle name: Edward. (Naturalization followed in 1947.) In December 1940 he met Delbrüiick at a conference in Philadelphia, Pennsylvania, and began a collaboration that was to last many years. Later their collaboration included Alfred Hershey. The three formed the core of the “phage group” that received the Nobel Prize in 1969. The field of study using the viruses that infect bacteria yielded valuable information on the subcellular mechanisms of mutation and reproduction. Delbriick was at Vanderbilt University, but they were able to work closely during summers at the Cold Spring Harbor Laboratory, alongside such leading geneticists as Hermann Müller and Barbara McClintock.

In 1941, with T. F. Anderson, Luria used one of the first electron microscopes to obtain a picture of bacteriophage. This significant achievement and others won for Luria a Guggenheim fellowship that he used to join research teams at Vanderbilt and Princeton.

In January 1943 Luria joined the faculty of Indiana University, where he proved to be an enthusiastic and popular professor. In the laboratory he demonstrated spontaneous mutations in bacteria, and Delbrück worked out the mathematical explanation for these events. Luria discovered the reactivation of bacteriophage killed by radiation, opening the field of DNA repair studies. His first graduate student at Indiana in 1947 was James Watson, who later elucidated the molecular structure of the gene and was awarded the 1962 Nobel Prize. Renato Dulbecco, also associated with Luria at Indiana, won the 1975 Nobel Prize for his work on the cultures of viruses and tumor cells.

Luria married Zella Hurwitz, then a graduate psychology student, on 18 April 1945. Their only child was born in 1948. In 1950 the Lurias moved to the University of Illinois, which was building a strong biochemistry and genetics program based on the research of Irwin Gunsalus and Sol Spiegelman. Luria continued his work on bacteriophage, discovering the restriction modification phenomenon, which was to become the foundation of genetic engineering.

In 1951 Luria was refused a passport as a result of his outspoken political activism. His socialism and commitment to justice and equality drew him to many causes, and he affiliated with like-minded intellectuals. He opposed McCarthyism and nuclear testing and supported organized labor and civil rights. He was still on the blacklist of the National Institutes of Health and actively opposing the Vietnam War when he learned of winning the Nobel Prize in 1969. He felt that his life in the Midwest contributed significantly to his personal sense of identity as an American intellectual.

The Midwest period came to an end in 1958 with a sabbatical year at the Massachusetts Institute of Technology (MIT), which offered him a faculty position in 1959. Luria was given the authority to build a strong biology department at MIT, while Zella joined the faculty at Tufts University. Luria was director of the Center for Cancer Research at MIT from 1974 to 1985, although he retired from most other official duties in 1978. The Lurias’ extensive involvement in the Boston and Cambridge communities was based as much on social and political interests as on scientific interests.

Luria’s writings, aside from scores of specialized scientific papers, drew a wide readership. His early textbook General Virology (1953) went through four editions. Life: The Unfinished Experiment (1973), a book written for the general public, won the National Book Award for science. A View of Life (1981), a beginning biology text written with Stephen Jay Gould and Sam Singer, was an admittedly unsuccessful attempt to reap the royalties that come from popular school titles. His autobiography, published in 1984, was a successful attempt to write a more literary than scientific narrative.

Luria died of a heart attack at his home in suburban Lexington, on 6 February 1991. Through his original experiments and as a prolific and persuasive writer and teacher, Luria contributed heavily to the growth and synthesis of the discoveries that formed the prevailing paradigm of molecular biology.

The personal papers of Salvador Luria are housed at the American Philosophical Society in Philadelphia, Pennsylvania. Luria’s autobiography, A Slot Machine, A Broken Test Tube: An Autobiography (1984), is a personal memoir containing as much motivational revelation as scientific explication. A biographical article by Tom Crawford is in Emily J. McMurray, ed., Notable Twentieth Century Scientists, vol. 3 (1995). Obituaries are in the New York Times (7 Feb. 1991) and Genetics 131 (May 1992): 1-4.

Michael F. Haines

LURIA, Salvador Edward

(b. 13 August 1912 in Turin, Italy; d. 6 February 1991 in Lexington, Massachusetts), geneticist, administrator, and writer who won the 1969 Nobel Prize in physiology or medicine for his work on viral and bacterial genetics.

Luria was the son of David Luria, an accountant who managed a printing business, and Ester Sacerdote, a homemaker. The Lurias were members of one of the most prominent Jewish families in Turin, and Salvatore (as his name was originally spelled) attended the Liceo d'Azeglio, one of the most prestigious high schools in northern Italy. Afterward he studied at the University of Turin medical school, where he took his degree with honors in 1935. He was then drafted into the Italian army as a medical officer. After he was discharged in 1937, Luria decided against a career in medicine and undertook more theoretical studies on radiology, physics, and mathematics in Enrico Fermi's laboratory at the Physics Institute of the University of Rome.

It was in Rome that Luria began the work that would lead to major discoveries about DNA (deoxyribonucleic acid) in the 1960s, and ultimately to his being awarded a Nobel Prize in 1969. (DNA is present in the chromosomes of all cell nuclei; the distinctive double helical strand is the chemical basis of heredity and carries genetic information for most living things.) Inspired by the work of the physicist Max Delbrück, he became interested in bacteriophage (phage), viruses that infect and kill bacteria. Luria went to France in 1938 when the situation for Italian Jews deteriorated after Italy became more closely tied with Nazi Germany. He briefly did research in Paris, and then, as the German Army approached the city, fled to New York in 1940 and obtained a position at Columbia University. In the early 1940s, funded by a Guggenheim Fellowship, he worked with Delbrückat Vanderbilt University and then accepted a faculty position in the microbiology department at Indiana University in Bloomington. There he met and married Zella Hurwitz, a psychologist, on 18 April 1945. They had one son, Daniel, who became a political economist. In 1947 Luria became a naturalized citizen of the United States.

At Bloomington, Luria discovered that bacteria, like higher organisms, can mutate or change genetically, and he developed a test to detect such mutations. He exposed bacteria to phage and then identified strains that continued to grow, indicating that they had mutated to become resistant to the damaging effects of the phage. Luria later discovered that phage can mutate. This work, along with that of two other phage researchers, Delbrück and Alfred Day Hershey, brought the study of genetics down to the molecular level. The trio began what came to be called the "phage group," and had a profound impact on genetic research of the 1960s. (The phage group was a group of researchers associated with the Cold Spring Harbor Laboratory, Long Island, New York. Today's comparatively sophisticated understanding of viruses is based on the work the phage group did in the 1960s.)

In 1950 Luria moved to the University of Illinois, where he remained until becoming professor and chair of the Massachusetts Institute of Technology (MIT) Department of Microbiology in 1959. At Illinois, Luria found that phage damaged by radiation can be "reactivated" by exchanging genes with other phage. He then accidentally discovered the process of restriction, where DNA is broken down into small pieces by protein catalysts called enzymes. Restriction enzymes later were crucial tools in what became known as genetic engineering, since they allowed biochemists to cut DNA and then take the pieces and insert them into other organisms. This ultimately led to the creation of genetically modified plants and animals.

By the 1960s Luria was busy building the MIT Department of Microbiology into one of the best in the United States. Deciding that phage research had gone as far as it could, he set his sights on different problems and became interested in cell membranes. He held a series of influential research conferences to draw attention to the field, and studied a class of proteins called colicins. Colicin produced by one type of bacteria can kill bacteria of other strains. Luria and his associates found that colicin works by creating a hole in the bacterial membrane and causing a fatal leakage of salts.

By the 1960s the scientific community had come to appreciate the work of the phage group. It was clear that work on phage had opened up a new era in biochemistry and molecular biology. It also was evident that DNA was the genetic molecule, and the work of the phage group in making that obvious was finally appreciated. In 1962 one of Luria's students, James Watson, received the Nobel Prize along with Francis Crick for discovering the structure of DNA. It was just a matter of time before Luria's earlier work on mutations in the DNA in bacteria and phage would also be recognized. Finally, in 1969, Luria was awarded the Nobel Prize in physiology or medicine along with the other two founders of the phage group, Delbrück and Hershey. The consensus by scientific observers at the time was that this award was long overdue, but the phage group's work was so revolutionary when it was first performed that its significance was fully appreciated only in the light of later work.

In 1972 Luria was asked by the president of MIT to create a Center for Cancer Research, and he recruited a stellar group of scientists, thus putting the center on a firm footing before his retirement in 1985. In 1984 Luria published his autobiography, A Slot Machine, A Broken Test Tube, the last of a series of books he wrote before his death from a heart attack in 1991 at his home in Lexington, Massachusetts. These include a textbook on viruses written in the 1950s and two books on biology written in the 1970s. One of these, Life: The Unfinished Experiment (1973) received the National Book Award in 1974.

A friendly and witty man, Luria had other interests besides science. He studied sculpture while on sabbatical in France in the 1960s and continued to create works for several years. Toward the end of his life he taught a world literatures course at MIT. Throughout his career Luria was interested in liberal political causes. He was active in the peace movement, being a critic of the Vietnam War and of U.S. defense spending.

Luria is considered one of the most influential molecular biologists of the twentieth century because of the breadth of his interests and the quality of his discoveries. He opened up several new fields, including phage research, as well as the study of mutations at the molecular level, the repair of radiation damage, and the enzymes needed for genetic engineering. His Nobel Prize capped a career that put him at the center of the most important discoveries in mid-century biochemistry.

Luria's papers are located at the American Philosophical Library in Philadelphia, Pennsylvania. Biographies of Luria include his autobiography, A Slot Machine, A Broken Test Tube (1984). See also "Salvador Edward Luria," in Modern Scientists and Engineers (1980) and James Watson, "Memoirs: Salvador E. Luria," in Proceedings of the American Philosophical Society (1999). Obituaries are in the New York Times (7 Feb. 1991) and the Washington Post (8 Feb. 1991).

Maura C. Flannery

LURIA, SALVADOR EDWARD

LURIA, SALVADOR EDWARD (1912–1991), U.S. biologist and Nobel Prize winner. Born in Turin, Luria studied medicine at the university there working under Giuseppe *Levi, and from 1938 to 1940 did research at the Institute of Radium in Paris. After the fall of France in 1940, Luria immigrated to the U.S., where he taught at Columbia (1940–42), Indiana University (1943–50), and the University of Illinois (1950–59), before becoming a professor of microbiology at the Massachusetts Institute of Technology in 1959. In 1964 he was appointed professor of biology at mit. He was an associate editor of the Journal of Bacteriology (1950–55), editor of Virology from 1955, and published General Virology (1953–67²). Luria was one of the pioneers of microbial genetics. In 1943, with Max Delbrueck, he showed that the appearance of bacteriophage-resistant strains of bacteria was the result of spontaneous mutations. The reasoning and design of this classic experiment became a model for subsequent research in vital and bacterial genetics. He dealt with lysogeny (the attachment of viral dna to the bacterial chromosome), transduction (the transfer of genetic material from one bacterium to another by a virus), and the control of phage properties by the bacterial host. Luria's later experiments, employing novel techniques, extended the principles of genetics to viruses and bacteria and formed an essential part of the foundation of the new science of molecular biology. In 1969 Luria was a corecipient (with Max Delbrueck and Alfred Hershey) of the Nobel Prize for physiology and medicine.

[Mordecai L. Gabriel]

Luria's open stance as a member of the peace movement may explain his appearing on a federal blacklist of 48 scientists drawn up by the National Institutes of Health in 1969. A critic of both American involvement in Vietnam and the Israeli invasion of Lebanon, he was also an opponent of what he regarded as insufficient safeguards on nuclear power, and in 1976 he and other scientists called for an end to the building of new atomic power plants.

Luria founded the mit Center for Cancer Research, and was director of the center from 1972 to 1985. In 1974 he won a National Book Award for Life: The Unfinished Experiment, a non-academic work. He officially retired from mit in 1978, but remained active there. From 1984 he served as senior scientist for the biotechnology company, the Repligen Corporation.

[Rohan Saxena (2^nd ed.)]

bibliography:

McGraw-Hill Modern Men of Science (1966), s.v.