Photo from the Nobel Foundation archive.
Born: 23 May 1925, Montclair, NJ, USA
Died: 2 February 2008, New York, NY, USA
Affiliation at the time of the award: University of Wisconsin, Madison, WI, USA
Prize motivation: "for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria."
Prize share: 1/2
It was long thought that bacteria multiply by dividing, so that all bacteria have the same genetic make-up. Joshua Lederberg and Edward Tatum demonstrated in 1946 that bacteria's genes can also change in a way similar to that of sexual reproduction seen in more complex organisms. Bacteria can go through a phase in which two bacteria exchange genetic material with one another by passing pieces of DNA across a bridge-like connection. Joshua Lederberg also proved the phenomenon known as transduction, in which DNA is transferred between bacteria via bacteriophages.