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RECOMBINATIONS OF MUTANT PHAGES OF BAC~.LUS

In a previous report, the recombination phenomenon was shown to occur in the plaque mutant phages of B. ~ g a l ~ i u m 899a (1). The present study is an amplification of thl.g work. Data are included on the percentages of recombination of the mutants isolated to date, and on the results of an analysis of these percentages. The B. megatherium system is unique in that all the mutants studied and most of the recombinants found can be readily recognized without recourse to special techniques. It is possible, in at least one case, to recognize plaques of phages with three mutations since each mutant produces its own characteristic effect on the plaque morphology. Phage recombination has been extensively studied by Hershey and coworkers (2-5) who have shown that the patterns of recombination of T2 coliphage mutants are essentially the same as those patterns found in the genetics of higher animals and are apparently genetic in nature. A further refinement of the work has been made by Doermann and Hill (6) using coliphage T4, a virus closely related to T2. Their findings were used to test a theory advanced by Visconti and Delbriick (7) which indicates that the coliphage T2 recombination can be explained on exactly the same basis as gene recombination in higher animals, with the major hypothesis that several rounds of mating occur during each infectious cycle. Doermann and Hill's results were in close agreement with those predicted by the hypothesis for five rounds of mating. Burner (8) and Hirst and Gotlieb (14) have been able to demonstrate recombination with influenza virus and Burner has suggested the possibility that the phenomenon, if it occurs naturally, might play a role in the sudden changes in virulence that are found.