Multiplicity Reactivation of Bacteriophage

Abstract

Luria and Dulbecco¹ formulated the most simple theory that could account for multiplicity reactivation. They supposed that each bacteriophage particle contains a certain fixed number of genetic units ; if one or more of these units is damaged by irradiation, the particle will not multiply unless it shares a bacterium with other particles which can supply undamaged versions of the units needed to make a complete set. Therefore the probability that a multiple-infected bacterium (multicomplex) contains a complete set of undamaged units should be simply a function of the number of units in a particle, the proportion of units which have been damaged by irradiation, the number of particles per bacterium (multiplicity), and the distribution of particles among bacteria. Early experiments showed that, within certain limits, this probability (termed ‘the survival of multicomplexes’) behaved in the expected way when multiplicity and degree of irradiation were varied.