|Papers of Nobel Laureate Salvador E. Luria Added
to Profiles in Science Web Site
What can a slot machine teach a scientist about mutations in bacteria?
Quite a lot, if the scientist is Salvador E. Luria (1912–1991).
He is the latest scientist to be added to the Profiles in Science
Web site, created by the National Library of Medicine, a part of
the National Institutes of Health in Bethesda, Maryland.
Early in 1943, Salvador Luria, an Italian-born bacteriologist
was trying to determine how bacteria become resistant to specific
viruses following infection: was the mutation to a resistant form
provoked by exposure to the virus? Or was it spontaneous and random?
The answer struck him one evening as he watched a friend playing
a slot machine.
Bacterial mutations, Luria realized, might occur in a pattern
analogous to payouts from the slots: slot machines return about
90 percent of money put into them, but distributed very unevenly — most
trials produce nothing, some yield very small amounts, and a few
yield jackpots. If random mutation was occurring in 20 different
bacteria cultures exposed to a virus, there would be resistant
colonies in some of the cultures, none in others, and very large
ones in a few. This is exactly what Luria found.
The discovery, made with Max Delbrück (who worked up a mathematical
proof that calculated mutation rates from the number of mutants
observed), marked the birth of bacterial genetics and demonstrated
the utility of bacteria for genetics research. Luria shared the
1969 Nobel Prize in Physiology or Medicine with Max Delbrück
and Alfred Hershey for their “discoveries concerning the replication
mechanism and the genetic structure of viruses.”
Profiles in Science has digitized and made available over the
World Wide Web a selection of the papers of Salvador Luria for
use by educators, researchers, and the public. The papers selected
for digitization are from the Luria materials in the American Philosophical
Society. This brings to 16 the number of notable researchers and
public health officials whose personal and professional records
are featured on the “Profiles in Science” site at http://www.profiles.nlm.nih.gov.
“Luria’s work with Max Delbrück brought bacterial viruses
to the center stage of genetics research in the 1940s, and he helped
develop bacterial genetics into one of the roots of molecular biology
as we know it today,” said Donald A.B. Lindberg, M.D., director
of the National Library of Medicine.
Born in Turin, Italy, on August 13, 1912, Luria graduated from
the University of Turin Medical School in 1935. He sought training
in radiation biology, and encountered Max Delbrück’s recent
theories about the gene as a molecule. Soon afterwards, Luria was
introduced to bacteriophages — viruses that infect bacteria.
By 1938, Luria, as a Jew, was barred from academic research fellowships
in Italy as that nation increasingly aligned itself with Nazi Germany.
He moved to Paris to continue his work. When the German army invaded
in 1940, Luria fled to the United States, where he finally met
Max Delbrück. Recognizing their common research interests,
they planned experiments to conduct over the summer of 1941 at
Cold Spring Harbor Laboratory on Long Island.
In 1943, Luria, inspired by the slot-machine analogy, demonstrated
that bacteria mutated spontaneously into phage-resistant forms.
Delbrück and he then developed the “fluctuation test” for
calculating bacterial mutation rates. This work provided statistical
evidence for the existence of genes in bacteria, and thus established
microbes as suitable subjects for genetics research.
During the 1940s, Luria continued his investigations into bacteriophage
and taught and mentored at Indiana University. (His first graduate
student was James Watson, who went on to discover the structure
of DNA with Francis Crick.)
In 1959, Luria joined the faculty at the Massachusetts Institute
of Technology as the chair of its new microbiology program. There
his research focus shifted to questions about cell membranes, and
enzymes within them.
Although he was not involved in resistance activities in Italy
or France during the 1930s and 1940s, Luria was almost always politically
engaged at some level after moving to the United States. He joined
biochemist Linus Pauling and many others in protesting nuclear
weapons testing during the 1950s and the building of new atomic
power plants in the 1970s. He was also an active participant in
the peace movement and was an outspoken critic of American intervention
The online exhibit features correspondence, published and unpublished
articles and monographs, photographs, lectures, speeches, and laboratory
notebooks from Luria’s files. An introductory exhibit section places
Luria’s achievements in historical context.
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