Falling in Love with Bacteria

Esther Zimmer fell in love with bacteria at Cornelius van Niel’s summer course in bacteriology.

After her first year of graduate school at Stanford University, during the summer of 1945, Esther attended Cornelius van Niel’s course in bacteriology. Van Niel taught graduate students, postdoctoral fellows, and senior scientists to cultivate and study the physiology of various bacteria.

Esther & van Niel J. Loeb Lab HMS 1945

In Pacific Grove, California, van Niel’s Course attracted “hundreds of applicants for each session, from which he was limited to choosing only a dozen students along with a dozen auditors,” wrote science historian Susan Spath. “The course played a significant role in training physical scientists who moved into biology after the war.”

Why was this course so popular that, as San Diego State University Professor Moselio Schaechter posed the question: “eminent biologists as well as their apprentices flocked to Pacific Grove as inexorably as the swallows coming (far down the coast) to Capistrano? The primary reason was that  van Niel “was not just a teacher but also a magician,” according to Schaechter, “all who took the course reported that they had come under his spell.”

Considering his far-reaching impact on the field of molecular biology, Cornelius van Niel may have been the most important teacher of microbiology of the 20th century.

With the emergence of the interdisciplinary field of molecular biology in the 1950s, more and more researchers required a foundation in the culture and study of bacteria. “Van Niel’s course played a major role in developing microbiology into a dynamic and respected discipline,” concluded Spath.

The next semester at Stanford, Esther Zimmer began to develop biochemical mutant bacteria, under Edward Tatum’s supervision. In 1946, the very same strains prepared by Esther were used in Joshua Lederberg’s breakthrough experiments demonstrating that bacteria could recombine genes.

That summer, at the Cold Spring Harbor Symposium, Zimmer and Lederberg met and fell in love. They married in December. The next year, they moved to the University of Wisconsin, where they established the first laboratory devoted to bacterial genetics. Esther Lederberg continued to work with bacteria and the plasmids they carry for the next 50 years.

Esther always appreciated how valuable the K-12 strain of E. coli was in her research: K-12 was fertile, capable of transferring genes in the early bacterial mating experiments. If Joshua had tried his first bacterial mating experiments with any other strain of E. coli, he would have failed. Esther discovered the reason for this, K-12 carried the F-factor (F for fertility), the first plasmid discovered in bacteria. K-12 also yielded the lambda bacteriophage, the most important bacteriophage of molecular biology.

No wonder then, that Esther christened her beloved beach house, “Kappadodici”, the Latin word for K-12. And she affectionately thought of her plasmids–she spent her last decades maintaining the collection of plasmids in Stanford’s Plasmid Reference Center–as chez microbe, “at the house of the bacteria.”


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