Max Ludwig Henning Delbruck

Max Ludwig Henning Delbruck was born on September 4, 1906 in Berlin Germany, the youngest of seven children of Hans Delbruck, a professor of politics at the University of Berlin and editor of a political journal. Delbruck grew up in the relatively affluent Grunewald suburb of Berlin, and lived in comfort until the outbreak of World War I, in which his older brother, Waldemar, was killed. His first interest in science was astronomy and astrophysics, later in his studies he switched to theoretical physics as it was during the time that the science of quantum mechanics was being discovered. In 1929 he received his Ph.D. in theoretical physics from the University of Gottingen. After a failed attempt to complete a thesis on novae he wrote a thesis on the quantum problem of the nonexistent diatomic lithium molecule.

After completing his thesis Delbruck spent 18 months at the University of Bristol (England) as a research assistant. After Bristol he received a Rockefeller Fellowship which allowed him to go to Copenhagen to study under Niels Bohr who influenced Delbruck's thinking about biology. In 1932 Delbruck accepted a position as an theoretical physics assistant to Lise Meitner, primarily to be near the Kaiser Wilhelm Institute for Biology. Hitler's rise to power in Germany caused a number of the Jewish scientists to emigrate from Germany, leaving the seminars less interesting to Delbruck. To make up for this loss Delbruck helped organize a group of physicists that met weekly to discuss physical problems. This group soon included biologists and a number of important papers emerged from these meetings, including an at first neglected paper on which Dulbruck collaborated about the nature of gene structure and mutations, that went on to be very influential.

In 1937 Dulbruck, on the strength of a second Rockefeller Fellowship, emigrated to the United States and took a position at the California Institute of Technology (Cal Tech) to study drosophila genetics. After having difficulty in learning the terminology of drosophila genetics Delbruck began studying bacterial phages with Emory Ellis. With the start of World War II, Delbruck's fellowship ran out and he took a position teaching at Vanderbilt University. The teaching position was only part time allowing Delbruck to spend the rest of his time doing phage research. During this period he collaborated with Salvador Luria, who was at the University of Indiana, and they demonstrated that bacterial resistance to phages was due to genetic mutation and not adaptive change. For this work they were awarded the Nobel Prize for Physiology or Medicine, along with Alfred Hershey, in 1969.

Phages are viruses that infect bacteria. Like the viruses that attack plant and animal cells, they insert their genetic material into host cell (in this case a bacteria) and use the host's genetic replication mechanisms to produce copies of its own genetic material. Bacteriophages are estimated to be the most widely distributed and diverse entities in the biosphere and they were among the first viral particles to be studied on a genetic level. Delbruk's work with Luria demonstrated that genetic mutation arises independent of selection pressure, that is mutation takes place randomly and is not influenced by changes or stressors in the bacteria's environment. At the time this was considered a huge advance in the understanding genetics and its importance has been compared to the work of Gregor Mendel.

In 1947 Delbruck returned to Cal Tech where he remained until 1977, doing research applying biophysical methods to the problems of sensory physiology. He is considered one of the most influential scientists who applied physical methods to biological problems.

Delbruck died on March 9, 1981.

References:

Delbruck, Max; interview by Carolyn Harding; at oralhistories.library.caltech.edu

Hayes, William;"Max Ludwig Henning Dulbreck" in Biographical Memiors Vol. 62; National Academy Press (1993)

Max Delbruck nndb entry

Luria-Delbruck experiment Wikipedia Entry