A CRITICAL TEST OF THE RECOMBINATION THEORY OF MULTIPLICITY REACTIVATION

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Abstract
Precise survival curves for phage production by bacteria multiple infected with phage T2 inactivated by ultra-violet were detd. for a wide range of u.-v. doses, with and without photoreactivation. The results are not compatible with the recombination theory, according to which multiplicity reactivation is due to a recombination of undamaged units from several parental particles. The ultimate slope of the survival curves for multiple infected bacteria is not equal to that of the curves for a single particle, but is actually about 1/5 of that slope; this asymptotic slope is reached very quickly. The intercept with the axis of ordinates are below 200 for each of the exptl. curves, although exceedingly high for the theoretical curves. The curves obtained after maximum photoreactivation are similar in general shape to those obtained in darkness but are not related to them by a constant dose reduction. Their ultimate slope is only a fraction (between 1/5 and 1/6) of the corresponding ultimate slope for bacteria infected with only one particle after photoreactivation. According to the present expts. the principal phenomenon in multiplicity reactivation is the reduction of the ultimate slope of the survival curves of multiple infected bacteria compared to single infected bacteria-, this may come about by a repair of u.-v. damage in multiple infected bacteria, or by a mechanism which would make certain parts of the phage particle dispensable in multiple infected bacteria. However, any substitutive mechanism by which a damaged part of activity in one of the infecting particles is simply replaced by a similar undamaged part or activity in another particle could not be reconciled with the present data since it would lead to predictions similar to those derived from the recombination theory.