In 1929, Delbrück received his PhD in physics from the University of Göttingen, after which he spent three years doing postdoctoral studies in England, Switzerland, and Denmark. During this time, he met Wolfgang Pauli and Niels Bohr, and his interactions with them aroused his interest in biology.
In 1932, he joined the Kaiser Wilhelm Institute for Chemistry in Berlin as a research assistant to Lise Meitner, and eventually took an interest in bacteriophages. He continued at the institute for the next five years, and progressed with his move from physics to biology.
During this period, he wrote several papers including an important one in 1933 on gamma rays. However, this paper lacked a concrete conclusion. Two decades later, Hans Bethe confirmed his observation and named it ‘Delbruck Scattering’.
In 1934, he became a member of a group of theoretical physicists and biologists who held intellectual private meetings. These meetings resulted in a paper on mutagenesis which eventually influenced the development of molecular biology in the late 1940s.
In 1937, a Rockefeller Foundation fellowship took him to the United States where he researched further on genetics and biochemistry at the California Institute of Technology (Caltech) in Pasadena.
A year later in 1938, he met a fellow biologist Emory Ellis, and together they explored bacteriophages and a mathematical system to analyze the results. They co-authored ‘The Growth of Bacteriophage’ in 1939.
His fellowship expired in 1939. Since World War II had begun and he disapproved of the Nazi regime, he decided to stay back in the US. He joined the faculty of Vanderbilt University in Nashville, Tennessee where he taught physics from 1940 to 1947.
In the meantime, he continued his phage research at the Cold Spring Harbour Laboratory on Long Island in New York. In 1941, he met Italian physician Salvador Luria from Indiana University, who was conducting bacteriophage research.
By 1943, their teamwork became famous in the scientific community. Their landmark paper, ‘Mutations of Bacteria from Virus Sensitivity to Virus Resistance’ is now considered the foundation of bacterial genetics.
Continue Reading Below
Also in 1943, he met microbiologist Alfred Hershey from Washington University and the ‘Phage Group’ conducted its first informal meeting on research involving bacteriophages.
In the Phage Treaty of 1944, the Phage Group defined some rules to make sure that findings on bacteriophages from different laboratories could be easily shared, evaluated and ascertained.
In 1945, he became a U.S. citizen and organized the first Phage Course at Cold Spring Harbour. The course eventually became a yearly episode attracting biologists, physicists and geneticists from all over the world.
In 1946, Delbrück's and Hershey's laboratories individually discovered that different bacteriophage strains that invade the same bacterial cell could randomly exchange genes to form new and unique viral strains. They named the phenomenon ‘Genetic Recombination’.
In 1947, he returned to Caltech as a professor of biology and remained there for the rest of his career. His 1949 lecture, ‘A Physicist Looks at Biology’ was reminiscent of his scientific journey.
In the early 1950s, he took up research on sensory perception, exploring the relationship between fungus, Phycomyces, and light. He formed a Phycomyces Group (alike the Phage Group) to collect and consider ideas.
Meanwhile, his work continued to influence bacteriophage research by other scientists, especially the determination of the three-dimensional, double-helix structure of DNA in 1953 by molecular biologist Francis Crick and physicist James Watson.
All through the 1950s and 1960s, researchers and students thronged him for his guidance and critical overview of their papers. In 1961, he took a two-year leave of absence from Caltech to help set up the Institute of Molecular Genetics at University of Cologne, Germany.
In 1969, the Phage Group received the Nobel Prize in physiology or medicine for their work in bacteriophages, particularly the mechanism of replication in viruses and their genetic structure. The committee also noted that “The honour in the first place goes to Delbrück who transformed bacteriophage research from vague empiricism to an exact science….”
Continue Reading Below
In the years following the Nobel Prize win, Delbrück continued his research on sensory perception. He retired from the faculty of Caltech in 1977.
In 1933, Delbrück wrote a significant paper on gamma rays, albeit without a concrete conclusion. It explored gamma rays' scattering by Coulomb field's polarization of vacuum. Two decades later, Hans Bethe confirmed the findings and named it ‘Delbruck Scattering’.
In their landmark paper of 1943, ‘Mutations of Bacteria from Virus Sensitivity to Virus Resistance’, Delbrück and Luria confirmed that phage-resistant bacterial strains developed through natural selection: once infected with a bacteriophage, the bacterium spontaneously changes so that it becomes immune to the invading virus. This paper is now regarded as the foundation of bacterial genetics.
In 1946, Delbrück's and Hershey's laboratories separately discovered that different bacteriophage strains on invading the same bacterial cell could randomly exchange genes to form new and unique viral strains. They named the phenomenon ‘Genetic Recombination’.
Personal Life & Legacy
Max Delbrück married May Bruce in 1941 and had four children together - Jonathan and Nicola, born in the mid-1940s and Tobias and Ludina, born in the early 1960s.
In his early life, Nazism was strongest in Germany. He was quite against their agenda and took up US citizenship in 1945.
His brother, Justus, and sister, Emmi however, stayed back in Germany to actively fight against the Nazi. Later, his brothers-in-law Dietrich Bonhoeffer and Klaus Bonhoeffer also joined the resistance. Eventually, they were tried by the People’s Court for plotting to assassinate Hitler and were executed in 1945.
He died of cancer on 9 March 1981, in Pasadena.