In addition to Delbrück, important scientists associated with the phage group include: Salvador Luria, Alfred Hershey, Seymour Benzer, Charles Steinberg, Gunther Stent, James D. Watson, Frank Stahl, and Renato Dulbecco.
Bacteriophages had been a subject of experimental investigation since Félix d'Herelle had isolated and developed methods for detecting and culturing them, beginning in 1917.
Delbrück, a physicist-turned biologist seeking the simplest possible experimental system to probe the fundamental laws of life, first encountered phages during a 1937 visit to T. H. Morgan's fly lab at Caltech.
Delbrück was unimpressed with Morgan's experimentally complex model organism Drosophila, but another researcher, Emory Ellis, was working with the more elementary phage.
However, as Ellis describes, Delbruck soon dispelled this initial reaction of disbelief by his own analysis of the phenomenon, and promptly joined in the work with enthusiasm, bringing to it his training in mathematics and physics, and intense interest in genetics.
Delbrück and Salvador Luria began a series of collaborative experiments on the patterns of infection for different strains of bacteria and bacteriophage.
The Luria–Delbrück experiment showed that bacteria, like other established model genetic organisms, have genes, and that these can spontaneously mutate to generate mutants that may then reproduce to form clonal lineages.
What he discovered was that when, after UV irradiation, two or more "dead" phage entered the same bacterial cell, they often became alive again and produced normal live progeny.
James Watson (future co-discover of the Watson–Crick structure of DNA in 1953, and winner of the Nobel Prize, 1962), was Luria's first graduate student at the Indiana University.
As his PhD thesis project, Watson showed that X-rayed phage can participate in genetic recombination and multiplicity reactivation.
Thus with no real reservations (except for occasional fear that he was not bright enough to move in his circle) he asked Luria whether he could do research under his direction in the spring term.
This procedure set the stage for Dulbecco to implement a comprehensive research program for quantitative studies on animal viruses to fathom their intracellular reproductive cycle.
[17][18] These genetic experiments, involving crosses of rII mutants, led to the finding of a unique linear order of mutational sites within the genes.
This result provided strong evidence for the key idea that the gene has a linear structure equivalent to a length of DNA with many sites that can independently mutate.
The ongoing informal discussions among these workers on the progress of their research led to a book by Stent entitled Molecular Biology of Bacterial Viruses (dedicated to Max Delbrück)[20] which was a lucid account of the accomplishments in this emerging field up to 1963.
Later, in his memoirs, Stent (1998) described some of the activities and personal interactions that illustrated the unique intellectual spirit of the phage group during its early crucial years (1948-1950).
[24][25] In 1995, Millard Susman published a retrospective article on the phage course as it was given over the years (1945 – 1970) both at Cold Spring Harbor (New York) and at the California Institute of Technology.
One noteworthy study was performed by Sydney Brenner and collaborators using amber mutants defective in the gene encoding the major head protein of phage T4.