Edward Tatum

American biochemist

• Born: December 14, 1909; Boulder, Colorado
• Died: November 5, 1975; New York, New York

American biochemist and geneticist Edward Tatum, in collaboration with Stanford University colleague George Beadle, conducted experiments in which the bread mold Neurospora crassa was exposed to X-rays, resulting in mutant strains. In 1941, they published an important paper explaining their “one gene–one enzyme” hypothesis: the idea that genes encode enzymes that accelerate chemical reactions in cells. The hypothesis is considered the first significant concept in molecular biology.

Primary field: Biology

Specialties: Genetics; biochemistry; cellular biology

Early Life

Edward Lawrie Tatum was the eldest son of Mabel Webb Tatum and Arthur Lawrie Tatum, a chemistry and pharmacology professor who held both PhD and MD degrees. Tatum attended the Laboratory School at the University of Chicago for his undergraduate work but transferred to the University of Wisconsin in 1931, earning his BA, MS, and PhD degrees within three years. Tatum’s thesis work included investigation into the role played by the B vitamin thiamine in bacterial metabolism. In 1934, he married June Alton with whom he would have two daughters, Margaret and Barbara.

In 1936, Tatum won a General Education Fellowship to study at the University of Utrecht, Holland. There he learned about concepts in microbial nutrition that would influence his later research. The following year, Tatum accepted a position as a research associate with George Beadle at Stanford University. They studied pigment production in Drosophila (fruit fly) larvae until 1941, when they decided the red bread mold Neurospora crassa was a better organism for their experiments.

Life’s Work

We now know that DNA is genetic material that encodes all the proteins in the body. When Tatum and Beadle were beginning their research, however, this had yet to be conclusively proven, and they designed an experiment to determine if DNA encodes special proteins called enzymes. They thought—correctly, as it turned out—that different DNA sequences, or genes, probably encoded each enzyme.

When Tatum and Beadle were conducting their experiments, X-rays were already known to damage the long, delicate DNA molecule. Tatum reasoned that if DNA functioned as the blueprint for enzymes, then damaged DNA should produce damaged, and probably nonfunctional, enzymes. In 1941, Tatum and his team began the long process of irradiating thousands of cultures of Neurospora and screening them for mutations. Since X-rays cause random mutations, there was no way to choose which genes to target, so many cultures were needed. The goal was to find surviving cultures with mutations in genes for nutritional enzymes.

A few cultures out of thousands were successful. There were mutations in genes encoding enzymes used to synthesize essential nutrients. The mutated cultures were identified because they could only survive when supplemented with essential molecules like thiamine or choline.

The team’s experiments demonstrated that enzymes are coded by DNA sequences called genes. In the same way that a blueprint details how a house is built, DNA encodes instructions for making proteins. What Tatum and Beadle didn’t understand at the time was that DNA also encodes many other proteins besides enzymes.

In 1945, Tatum left Stanford University to teach at Yale University, where he collaborated with a brilliant young scientist named Joshua Lederberg. They adapted many of Tatum’s Neurospora techniques to the study of bacteria, which resulted in the discovery of bacterial conjugation, which is the sharing of genetic information between a donor cell and a recipient. Since many bacteria reproduce by binary fission (splitting in half), they often produce offspring that are identical to the parent cell. Tatum and Lederberg proved that some bacteria can share genes in a process analogous to sexual reproduction.

Tatum’s bacterial research used many of the same experimental design principles that proved useful in the Neurospora work. Like the Neurospora experiments, the bacterial research utilized strains of nutritional mutants that required supplementation to survive. In the first documented example of conjugation, two strains of bacteria with different mutations shared genes and repaired each other’s deficiencies. It was later discovered that genes transferred by conjugation are carried on small circles of DNA called plasmids, which exist in addition to the larger circular chromosome found in most bacteria. Modern genetic engineering often makes use of plasmids to transfer genes from one organism to another.

In 1948, Tatum returned to Stanford as a professor of biology. He was especially interested in teaching the genetics of Escherichia coli (commonly called E. coli), a bacterium commonly used in laboratories. Tatum was promoted at Stanford, becoming chair of the biochemistry department in 1956. That same year, he and his first wife divorced. Within a year of his divorce, he married Viola Kantor.

In 1957, Tatum left Stanford again, this time for a professorship at the Rockefeller Institute for Medical Research in New York City (now Rockefeller University). The next year he and George Beadle were honored with half of the Nobel Prize in Physiology or Medicine for their groundbreaking research on the genetics of Neurospora. The other half of the prize went to Tatum’s graduate student, Joshua Lederberg, for the discovery that bacteria are capable of mating and exchanging genes. In addition to the Nobel Prize, he was previously awarded the prestigious Remsen Award of the American Chemical Society in 1953.

After Kantor died in 1974, Tatum married his third wife, Elsie Berglund. Burglund survived Tatum, who was a heavy smoker, when he died from heart failure and complications of chronic emphysema on November 5, 1975.

Impact

The “one gene–one enzyme” hypothesis was a major discovery that explained how genetic traits are passed from parent to child. It also laid the foundation for the field of genetic engineering. Scientists have used genetic engineering to help treat inherited diseases as well as to improve agriculture production. Other applications of the technology, such as cloning, have stimulated debate among ethicists.

One of the spin-offs of Tatum and Beadle’s Neurospora work was the large-scale production of the infection-fighting antibiotic penicillin. (Penicillin is produced naturally by some species of fungus in order to kill off their bacterial competitors.) In 1944 during the US involvement in World War II, Tatum began working with the Office of Scientific Research and Development to mass-produce penicillin in order to treat the infected wounds that many soldiers were developing. Thousands of lives were saved as a result.

Tatum’s bacterial conjugation research was significant because it proved that through conjugation, bacteria can pass on traits such as resistance to antibiotics. Conjugation can take place anywhere bacteria live, especially in hospital environments where many strains of bacteria intermingle. It may take years to develop an antibiotic, but once a single cell evolves to withstand it, that trait quickly spreads through the entire population of bacteria.

Bibliography

Davis, Rowland H. Neurospora: Contributions of a Model Organism. New York: Oxford UP, 2000. Print. Explores the laboratory methods, physiology, development, and biochemistry of Neurospora and summarizes over seventy-five years of research. Tatum and Beadle’s work is highlighted.

Gillham, Nicholas. Genes, Chromosomes, and Disease: From Simple Traits, to Complex Traits, to Personalized Medicine. Upper Saddle River: Pearson, 2011. Print. Provides an overview of medical genetics and discusses the social implications of genetics.

Horowitz, Norman H. “Neurospora and the Molecular Revolution.” Genetics 151.1 (1999): 3–4. Print. Explains the impact of Neurospora research on molecular genetics.

Lederberg, Joshua. “Edward Lawrie Tatum.” Annual Review of Genetics 13 (1979): 1–5. Print. Focuses on the life and work of biochemist Edward Tatum and covers his contributions to the foundation of biochemical genetics.

Raju, Tonse N. K. The Nobel Chronicles: A Handbook of Nobel Prizes in Physiology or Medicine, 1901–2000. Bloomington: 1st Books, 2002. Print. Profiles recipients of the Nobel Prize in Physiology or Medicine and describes their contributions to genetics.