Chapter 29 : Joshua Lederberg and the “Cellularity” of Bacteria

Abstract:

Joshua Lederberg died recently. His is a revered name among our older readers, and we assume that many younger ones also know of him. But just in case, let us mention some of what made him a giant in modern biology. He is best known for finding that bacteria have sex, that is that they can undergo cell-to-cell conjugation. He then discovered (with Norton Zinder, a graduate student) that genes can also be exchanged via phages: transduction. Thus, Lederberg discovered two of the three major mechanisms for gene transfer in bacteria. The third, transformation by naked DNA, had already been discovered, or else—who knows?—he might have found that one, too. He then entered the fray related to the origin of mutations. For this purpose, he invented, together with his wife, Esther, the replica plating technique, which allowed him to demonstrate that mutations were spontaneous and random, not induced by something in the environment. He did this by comparing a mutant colony identified on a replica plate with the corresponding colony on the master plate, and showing that they both had the same properties. That ended the argument, at least for the time.