Joshua Lederberg, 82, Genetics Pioneer

Joshua Lederberg, who died Saturday at 82, was awarded a Nobel Prize for discovering that bacteria can reproduce sexually. His experiments laid the groundwork for modern microbiology, genetic engineering, and gene therapy.

A prominent public intellectual, he was among the first to raise questions about introducing germs into outer space and served as a science advisor to several presidents and agencies, including NASA and the Arms Control and Disarmament Agency.

Lederberg served as president of New York's Rockefeller University from 1978–1990. He was also a prolific writer who was among the first to anticipate the ethical dilemmas posed by genetic manipulation.

Born May 23, 1925, in Montclair, N.J., Lederberg was the son of a rabbi who moved his family to New York City. Already a scientific prodigy while attending Stuyvesant High School, he conducted original research in his spare time and graduated from Columbia University with honors at 19. In 1944, he enrolled in medical school at the Columbia University College of Physicians and Surgeons, but he left after two years to study microbiology at Yale University. It was while studying E. coli bacteria at Yale that Lederberg established that bacteria could combine their genetic material and pass it to offspring, overturning the orthodoxy of the time that held that bacteria reproduced simply by dividing. With colleagues, he demonstrated that there were two processes for transferring genetic material: conjugation, in which bacteria transfer chromosomes, and transduction, in which viruses incorporate bits of genetic material.

In 1947, while still a Ph.D. candidate at Yale, Lederberg became an assistant professor of genetics at the University of Wisconsin. He made a series of fundamental discoveries in genetics, including how mutations occur, how penicillin works, and how bacteria develop resistance to it. Considered a laboratory whiz, he developed several techniques, including replica plating, a technique for identifying genetic mutations that he created with his first wife, Esther Zimmer, also a geneticist.

In 1958, at age 33, he shared the Nobel Prize in physiology or medicine with two other genetics pioneers, George Beadle and Edward Tatum, his professor at Yale.

With Sputnik and the rise of the American space program, Lederberg coined the term "exobiology" to describe the study of life outside of Planet Earth. It was partly due to his leadership that astronauts underwent a period of quarantine upon returning to earth. He later became a consultant to the Viking missions to Mars.

Lederberg left Wisconsin in 1959 and joined the Stanford University School of Medicine, where he was chairman of the department of genetics and also was professor of biology and computer science. His optimism about the capacities of computers did not extend to the cognition of the humans who had designed them: He lamented the "archaic clumsiness of our basic mechanisms of communication." In "Man and His Future," Lederberg wrote: "Man's dilemma is the discrepancy between the size of his population and the complexity of his institutions, on one hand, and his individual feebleness, measured as a data input rate of no more than fifty bits per second."

He lectured widely on the relationship between science and society, and served as an advisor on biological warfare to the World Health Organization.

After stepping down as president of Rockefeller in 1990, Lederberg became president emeritus of molecular genetics and informatics. He returned to the laboratory, studying how the activation of genes alters their vulnerability to mutagenesis.

He continued to write, and in recent years he developed a concept of the human body as a "microbiome" — a kind of superorganism whose genome included not only its own cells but also the genomes of the bacteria and viruses who that inhabit it.

He was awarded the National Medal of Science in 1989 and Presidential Medal of Freedom in 2006, as well as many honorary degrees.

Lederberg is survived by his wife, Dr. Marguerite Lederberg; his children Anne Lederberg and David Kirsch; and two grandchildren.