Esther Lederberg

Esther Miriam Zimmer Lederberg (December 18, 1922 – November 11, 2006) was an American microbiologist and a pioneer of bacterial genetics. She discovered the bacterial virus lambda phage and the bacterial fertility factor F, devised the first implementation of replica plating, and furthered the understanding of the transfer of genes between bacteria by specialized transduction.

Lederberg also founded and directed the now-defunct Plasmid Reference Center at Stanford University, where she maintained, named, and distributed plasmids of many types, including those coding for antibiotic resistance, heavy metal resistance, virulence, conjugation, colicins, transposons, and other unknown factors.

As a woman in a male-dominated field and the wife of Nobel laureate Joshua Lederberg, Esther Lederberg struggled for professional recognition. Despite her foundational discoveries in the field of microbiology, she was never offered a tenured position at a university. Textbooks often ignore her work and attribute her accomplishments to her husband.

Early years Esther Lederberg, Gunther Stent, S. Brenner, J. Lederberg, 1965

Esther Miriam Zimmer was the first of two children born in the Bronx, New York, to a family of Orthodox Jewish background. and Pauline Geller Zimmer. Her brother, Benjamin Zimmer, followed in 1923. Zimmer was a child of the Great Depression, and her lunch was often a piece of bread topped by the juice of a squeezed tomato. Zimmer learned Hebrew and she used this proficiency to conduct Passover seders. She was awarded a scholarship to attend New York City's Hunter College starting that fall. graduating cum laude in 1942, at the age of 19. In 1944 she won a fellowship to Stanford University, working as an assistant to George Wells Beadle and Edward Tatum. Lederberg moved to Yale's Osborn Botanical Laboratory and then to the University of Wisconsin after her husband became a professor there. She completed her doctorate under the supervision of R. A. Brink in 1950. did early research on the relationship between transduction and lambda phage lysogeny, discovered the E. coli F fertility factor with Luigi Luca Cavalli-Sforza (eventually publishing with Joshua Lederberg), devised the first successful implementation of replica plating with Joshua Lederberg, and helped discover and understand the genetic mechanisms of specialized transduction. These contributions laid the foundation for much of the genetics work done in the latter half of the twentieth century. Because of her work, she is considered to be a pioneer in bacterial genetics. In 1956, Esther and Joshua Lederberg were honored for their fundamental studies of bacterial genetics by the Society of Illinois Bacteriologists, which awarded them the Pasteur Medal. Her studies showed that λ had both a typical lifestyle in which the phage rapidly made many copies of itself before bursting out of the E. coli host and an alternative lifestyle in which the phage existed quietly within E. coli as just another genetic marker.

Esther and Joshua Lederberg demonstrated that λ, in its quiescent form, genetically mapped near the E. coli genes required for metabolism of the sugar galactose (gal). The Lederbergs proposed that the genetic material of λ physically integrated into the chromosome next to the gal genes and subsequently replicated as a prophage along with the DNA of the host bacterium.

Following publication of her studies on λ over several years, Lederberg presented her findings at international conferences. In 1957, Lederberg gave a talk on λ lysogeny and specialized transduction at the Symposium of Bacterial and Viral Genetics in Canberra, Australia. In her own words:

In terms of testing available markers ... the data showed that there was a specific locus for lysogenicity. ... In the course of such linkage [genetic mapping] studies...one day, ZERO recombinants were recovered....I explored the notion that there was some sort of 'fertility factor' which if absent, resulted in no recombinants. For short, I named this F. Scientists had been struggling for a reliable solution for at least a decade before the Lederbergs implemented it successfully. Less efficient forerunners to the methodology were toothpicks, paper, wire brushes, and multipronged inoculators. Biographer Rebecca Ferrell believes that the method Lederberg invented was likely inspired by using her father's press at his work, pressing a plate of bacterial colonies onto sterile velvet, after which they were stamped onto plates of media with different ingredients, depending on the desired traits the researcher wished to observe. The spontaneous nature of mutations was previously demonstrated by Luria and Delbrück. However, many scientists failed to grasp the mathematical arguments of Luria and Delbrück's findings, and their paper was either ignored or rejected by other scientists. The controversy was settled by the Lederbergs' simple replica-plating experiment. As director of the PRC, she organized and maintained a registry of the world's plasmids, transposons, and insertion sequences. The sequential numbering continued until her retirement. However, although Esther Lederberg was a pioneer research scientist, she faced significant challenges as a woman scientist in the 1950s and 1960s.

After her foundational discoveries of the F factor and λ in graduate school, Joshua Lederberg stopped her from conducting additional experiments to follow up on her discoveries. According to Esther, Joshua, as her thesis advisor, wanted her to finish her PhD dissertation. Her graduate school advisor, R.A. Brink, may not have recognized the significance of her discoveries. She may have been fully recognized for her discoveries if she were allowed to pursue them immediately. Instead, the delay hurt her legacy as an independent research scientist, and her findings on bacterial sex are now credited primarily to her husband. In fact, most textbooks highlight Joshua Lederberg's role in the discoveries made jointly with Esther. The lack of credit Esther Lederberg is given for development of the replica plating technique has been cited as an example of the Matilda effect, in which discoveries made by women scientists are unfairly attributed to their male colleagues. By the time Joshua won the Nobel Prize in 1958, the research centers that were recruiting him saw Esther as his wife and research assistant rather than an independent scientist.

Lederberg was excluded from writing a chapter in the 1966 book Phage and the Origins of Molecular Biology, a commemoration of molecular biology. According to the science historian Pnina Abir-Am, her exclusion was "incomprehensible" because of her important discoveries in bacteriophage genetics. Abir-Am attributed her exclusion in part to the sexism that prevailed during the 1960s.

As Luigi Luca Cavalli-Sforza later wrote, "Dr. Esther Lederberg has enjoyed the privilege of working with a very famous husband. This has been at times also a setback, because inevitably she has not been credited with as much of the credit as she really deserved. I know that very few people, if any, have had the benefit of as valuable a co-worker as Joshua has had." Like many other women scientists at Stanford University, Lederberg struggled for professional recognition. As her husband began his tenure as the head of the genetics department at Stanford in 1959, she and two other women petitioned the dean of the medical school over the lack of women faculty. She was eventually appointed a faculty position as research associate professor in the department of microbiology and immunology, but the position was untenured. Later in 1974 as a senior scientist, she was forced to transition to a position as adjunct professor of medical microbiology, which was effectively a demotion. Her short-term appointment was to be renewed on a rolling basis and was dependent on her securing grant funding. She played the recorder and in 1962 founded the Mid-Peninsula Recorder Orchestra, which plays compositions from the 13th century to the present.

Lederberg also loved the works of Charles Dickens and Jane Austen. She belonged to societies devoted to studying and celebrating these two authors, the Dickens Society of Palo Alto and the Jane Austen Society.

Personal life

She married Joshua Lederberg in 1946; they divorced in 1968.