Lysogeny at Mid-Twentieth Century: P1, P2, and Other Experimental Systems

Most of us doing research have a preferred material, a set of well-tried techniques, a standing list of unsolved problems, ways of looking at or of doing things, which we share to a large extent with colleagues in the same laboratory and others in the same area of specialization, be they friends, former associates, or competitors. All this and more is encompassed by the concept of "experimental system" as introduced and used by Hans-Jörg Rheinberger (76, 77), a historian of science. His concept, rather flexible and rich in metaphors, may be easily adapted to the present narrative, which proceeds from a personal view rather than from a critical historical examination. A careful restriction of material, techniques, and nomenclature allows more constructive interactions between different laboratories and different generations of scientists in the same field. Of course, carried out to excess, this process will stifle developments in new areas and defer some discoveries. Max Delbrück, who in the early forties had forcefully advocated the study of bacteriophage as the royal road to the secrets of replication and recombination, was quite outspoken about the necessity for workers on that road to use a common material (the T phages in Escherichia coli B) and precisely standardized techniques (1). Of course, the T phages are generally virulent, take-no-prisoner parasites of bacteria and thus could not instruct us about the more shadowy interactions between "weaker" bacteriophages and their bacterial hosts: about lysogeny, where infection meets heredity.