American microbiologist Esther Miriam Zimmer Lederberg (1922 – 2006) discovered the bacterial virus Lambda phage and the bacterial fertility factor F (F plasmid). Esther Lederberg was not given credit for her scientific contribution because of her gender. While her husband, her mentor, and another research partner won the 1958 Nobel Prize in Physiology or Medicine for discovering how genetic material was transferred between bacteria, Esther wasn’t even mentioned in the citation, even though her work significantly contributed to the discovery.

Esther Miriam Lederberg was born in Bronx, New York, into a humble family, that moved from Sereth, Bukowina, a part of the Austro-Hungarian empire, and settled in the United States. At the age of 16, she won a scholarship to study biochemistry at Hunter College, City University of New York. In 1942, Esther won a fellowship at Stanford University to take a master’s course in genetics. There she struggled to make ends meet. It has been mentioned in reports as recalled by Esther that she had sometimes eaten frogs’ legs leftover from laboratory dissections.

Esther met her future husband Joshua Lederberg at Stanford. They moved to the University of Wisconsin, where they would begin years of collaboration. Esther also earned her Ph.D. there. Throughout the 1950s, they published papers together and apart as both made discoveries about bacteria and the genetics of bacteria.

Esther Lederberg’s contributions to the field of microbiology were enormous. In 1950, she discovered lambda phage, an example of a new type of virus called a bacteriophage, which lives inside the DNA of bacteria, multiplying in response to a trigger. She developed an important technique known as replica plating, still used in microbiology labs all over the world. Along with her husband and other team members, she discovered the bacterial fertility factor.

She established the Plasmid Reference Center at Stanford University and directed it until 1985.