Inside Salk; Salk Insitute

Serendipity and science

William Brody

William R. Brody, M.D., Ph.D.
Irwin M. Jacobs Presidential Chair


For our readers who are not scientists, I am going to let you in on a big secret ingredient that underlies many major scientific discoveries. One short word describes this ingredient, and it is simply this: luck

Not only luck, but hopefully good luck. While most of us were taught in school about the scientific method—rational thinking, deductive and inductive reasoning—and these are indeed important ingredients, the fact is, chance plays a significant role in scientific discovery. Sometimes it is an experiment that goes awry and produces unexpected (and sometimes unwanted) results that ultimately lead to a whole new paradigm. This was the situation for Alexander Fleming in 1928, when he left a stack of bacterial cultures in Petri dishes in his lab to be discarded while he went on vacation. By mistake, they were not discarded, and when he returned from vacation, he noticed that a fungus had grown in one of the dishes, and where there was fungus, the bacteria failed to grow. This chance observation led to the discovery of penicillin.

Professor Ed Callaway, a neuroscientist at Salk, was studying the electrical behavior of single neurons in the brain and wanted to know which other neurons in the cortex were sending signals to a particular neuron. This difficult challenge had never been solved, but a chance conversation between Callaway and Salk professor John Young, a virologist, led to an intriguing idea. Young theorized that the rabies virus, because it infected neurons in the brain by traveling along the axon sheath (the "cable" that transmits signals from one neuron to another), could be used as a sophisticated agent to identify the connections between nerve cells.

In order to get the virus to infect the single neuron, it required substantial genetic modification. A series of steps, including inserting a snippet of DNA that would allow the virus to become fluorescent green, ultimately allowed Callaway to identify a single neuron, record its electrical activity and then shine a laser on the brain. Amazingly, the connected neurons show up as bright green spots in the microscope.

The "secret sauce" of Salk scientific discovery is the unique character of our institute. Because there are no departments or divisions and also because the architectural design of the Salk facilitates interaction among scientists in the laboratory, discussions such as the one between Callaway and Young are commonplace. Facilitating interaction among the best minds in seemingly unrelated fields is one important aspect of scientific (or should I say "serendipitous") discovery.

Of course, luck is no substitute for expertise and hard work, leading to two corollaries of scientific discovery that are also important:

From Louis Pasteur: "Chance favors the prepared mind."

And from an anonymous source: "The harder I work, the luckier I get!"