Max Delbrück

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.

Max Delbrück was born on 4 September 1906, in Berlin, Germany. He belonged to a family of academicians; his father, Hans Delbrück was Professor of History at the University of Berlin, while his maternal great-grandfather was the famous chemist, Justus von Liebig.

Growing up in Berlin he witnessed both, the prosperity before and the despair after the First World War. As a child, he was interested in mathematics and astronomy.

In 1924, he registered with the University of Tübingen, but changed colleges several times before joining the University of Göttingen. In college, he changed his subject from astrophysics to theoretical physics.

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.

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’.