As a young lab leader at the University of Wisconsin in the 1950s, Joshua Lederberg and his first wife Esther, a microbiologist, would invite lab members to their home once a week to discuss significant recent advances in microbial genetics. Lederberg would sit silently on the floor, listening, recalled Gaylen Bradley, who was a postdoc in Lederberg's lab between 1954 and 1956.

"Josh would listen, and then at the end make some sort of sense of our immature, if you will, interpretations of the data," he said. "It was always an impressive finale when Josh would finally enter the conversation."

"Josh had the ability to recognize very easily what the important questions in science were," said Stanley Cohen, chair of the genetics department at Stanford University School of Medicine. "Whatever subject he worked in, he was really at the forefront in terms of creativity."

Lederberg passed away on Saturday (February 2) at the age of 82.

Just days before he learned he was to receive the Nobel Prize in Medicine in 1958, Lederberg accepted a position at Stanford as the first chair of its fledgling genetics department. He continued his work in genetics, but also became interested in computer applications to science, as well as the biological side of space exploration. In 1964, while developing the miniature instruments that could identify organic compounds found in space (used in the 1976 Viking Mars mission), he began collaborating with Edward Feigenbaum, a Stanford computer scientist and artificial intelligence expert.

The duo created a computer program called DENDRAL that modeled the thinking process of chemists in order to interpret data from chemical analyses. It was one of the first major applications of artificial intelligence, and they went on to build similar programs for medicine and for molecular genetics, said Feigenbaum. "He would just reach down into problems several levels deeper than anyone else in our team," he said. He characterized Lederberg as a person with "the absolute greatest integrity," adding that "he had absolutely no hidden agenda except the truth."

Cohen recalled the kindness and generosity of a man he considered a close friend, a mentor and a role model. Lederberg "would take the time to contact his colleagues - this was initially before Email - with little sticker notes and reprints and other things, if he came across an item he thought was of interest," said Cohen.

Lederberg left Stanford to serve as president of Rockefeller University between 1978 and 1990. At such a small institution, said James Darnell, a molecular biologist at Rockefeller, there was plenty of opportunities to interact with the president. At that time, Rockefeller had a hierarchical structure in which researchers rose through the ranks to become independent lab heads. Darnell and other staff members were pushing to recruit younger staff from outside the university who would be able to run their own labs. Lederberg was very supportive of the effort, Darnell said, and the two became close friends.

"His fantastic memory and his eclectic interests were obvious to anyone who sat down with him," said Darnell, "and his ability to understand anything you were telling him was instantaneous." In the basement of the Rockefeller building housing the president's office stood evidence of Lederberg's attention to detail - "an endless row of steel cabinets where he kept notes about everything in the world."

Starting from his first stint in science policy as a member of the President's Science Advisory Committee in 1957, Lederberg also took an active role in advising the government and the public on scientific issues on topics ranging from nuclear and biological weapons and biotechnology to mental health and antimicrobial resistance.

"He was a person who thought more broadly and deeply about science and societal issues relating to science than anyone I had ever met," said Cohen. "He was in many ways a Renaissance man."