DELBRÜCK, Max Ludwig Henning

(b. 4 September 1906 in Berlin, Germany; d. 10 March 1981 in Pasadena, California), geneticist called the father of molecular biology who won the 1969 Nobel Prize in physiology or medicine for his cross-disciplinary approach to the study of viruses.

Delbrück was born to Hans Delbrück, a professor of history at the University of Berlin, and Lina Thiersch Delbrück, a granddaughter of the scientist Justus von Liebig, who is considered the originator of organic chemistry. The youngest of seven children, Delbrück grew up in a very active family and among members of the academic, professional, and merchant classes. As a youngster he developed a strong interest in astronomy, partly as a way to distinguish himself among so many strong personalities in his family and among their friends. However, Max Planck, a boy in the neighborhood who grew up to be a physical chemist of high distinction, became a mentor and a lifelong friend to Delbrück. Their relationship shifted Delbrück's focus from astrophysics to theoretical physics during the latter days of his graduate studies at the University of Göttingen, just after the breakthrough discoveries that opened the field of quantum mechanics. Delbrück received his Ph.D. in 1930.

Delbrück took three postdoctoral years (1929–1932) in England, Switzerland, and Denmark. He began a lifelong association with Wolfgang Pauli and Niels Bohr, and it was Bohr who first influenced Delbrück's final turn toward biology and cross-disciplinary studies in science. Delbrück moved to Berlin in 1932, where he wrote a very influential paper, Über die Natur der Genmutation und der Genstruktur ("On the Nature of Gene Mutation and Gene Structure"), with Nikolai Timoféeff-Ressovsky and K. G. Zimmer on mutagenesis that was published in 1935 and later reprinted in Erwin Schrödinger's essay, What Is Life? (1944). This association and the paper laid the foundation for the rapid development of molecular genetics in the 1940s, 1950s, and 1960s.

In 1937 Delbrück immigrated to the United States with the help of a Rockefeller Foundation fellowship, which provided him with greater freedom to pursue his research interests in biology. He went to the California Institute of Technology because of its strength in fruit fly genetics and ended up working with Emory L. Ellis in phage research. Ellis introduced him to bacteriophages, or phages, viruses that affect bacteria, an area of study that appealed strongly to Delbrück's physics-trained mind. Like the hydrogen atom, the simplest form of matter, the bacteriophage was then considered the simplest form of life. When the fellowship ran out in 1939 and World War II started, Delbrück decided to stay in the United States, accepting an instructorship in the physics department at Vanderbilt University in Nashville, Tennessee. In 1941 Delbrück married Mary Adeline Bruce, and in later years they had four children.

During World War II, around 1941, Delbrück began his association with the Cold Spring Harbor Laboratory of Quantitative Biology on Long Island, New York, and with Salvador E. Luria and other well-known luminaries in the field of biology. This began what became known as the Phage Group, which eventually originated fluctuation theory. At this point, Delbrück and Luria began studying bacteria and viruses to determine their mode of transmission. Much to their surprise, they discovered that viruses and bacteria were capable of transferring their DNA in order to replicate rapidly. Research began into the mechanism of the transfer, and Luria came up with the idea of treating the bacteria as though they were slot machines. Exposure to viruses caused the bacteria to die, but those that survived would spring back with continued growth and take back the territory formerly possessed by the viruses. Thus the scientists could determine whether the survival was based on chance or if the bacteria were mutating in response to the challenge from the viruses. This discovery marked the beginning of phage research and began science's present-day insight into the nature of viruses. Among other discoveries and accomplishments from the Phage Group were the mutual exclusion principle, the fluctuation test, and the phage theory. Delbrück and Luria's students included James Watson, Renato Dulbecco, and other interested physicists and biochemists such as Leo Szilard, the father, with Enrico Fermi, of the nuclear chain reaction, and the atomic scientist Philip Morrison.

Delbrück became a U.S. citizen in 1945, and in the early 1950s his research interests shifted from molecular genetics to sensory physiology and phage research. One of the first grants the National Science Foundation ever awarded was to Delbrück for research. The study was called "Mechanisms Underlying Genetic Recombination in Bacteria." The results of Delbrück's work and teaching contributed to the rise of modern molecular genetics. Initially he began work on sporangiophores of Phycomyces to study stimulus transductions at the molecular level and to determine transducer processes of sense organs in general. In 1962 Delbrück was instrumental in setting up an institute of molecular genetics at the University of Cologne to demonstrate the possibilities behind modern interdisciplinary research within Germany and to promote the field of molecular genetics there. This institute was dedicated on 22 June 1962, with Niels Bohr the primary speaker, one of his last appearances.

Delbrück won the 1969 Nobel Prize in physiology or medicine using a cross-disciplinary approach to the study of viruses by fusing biochemistry, genetics, and physical principles to study replication mechanisms and the genetic structure of viruses. He shared the prize with Alfred Day Hershey and Luria, and a brief biography refers to him as "one of the founding fathers of modern genetics." Also in 1969 both Luria and Delbrück won the Louisa Gross Horowitz Prize for their contributions to the understanding of the genetics of bacteria and bacteriophages.

In 1978 Delbrück was diagnosed with multiple myeloma. Successful treatment prolonged his life for three years, and then a few months before his death in 1981, he also had a mild stroke that affected his vision.

Scientists writing about this era in genetics who worked closely with Delbrück refer often to his happy spirit, quick wit, and generosity of spirit. In 1966 Delbrück's colleagues honored his sixtieth birthday by publishing Phage and the Origins of Molecular Biology, a collection of essays by Phage Group members. It is remarkable to read the list of luminaries that Delbrück brought together at Cold Spring Harbor. He appears to have been a wonderful catalyst and mentor to many. His was a remarkable and intelligent influence on modern gene research, molecular biology, phage theory, and tumor virology. Perhaps his greatest strength was his broad, deep knowledge of several scientific fields and his ability to intermingle biochemistry, genetics, and physical principles in his research and thinking.

For more information, see Ernst P. Fischer and Carol Lipson, eds., Thinking About Science: Max Delbrück and the Origins of Molecular Biology (1988). See also Robert S. Edgar, "Max Delbrück," Annual Review of Genetics 16 (1982): 501–505, and William Hayes, "Max Ludwig Henning Delbrück," National Academy of Sciences. Biographical Memoirs 62 (1993): 67–117. An obituary is in the New York Times (13 Mar. 1981).

Kim Laird