THE PLAQUE DISSOCIATION PHENOMENON IN BACTERIAL VIRUSES AND ITS GENETIC ANALYSIS

Abstract

1) Recently we have found an interesting plaque dissociation phenomenon in some viral strains of S. gallinarum (Akita strain) phage and S. sendai (S. 71 strain) phage. These viruses were called as s type virus.2) The pure stock of s type virus forms the so-called sector type plaques on Sg or PA. The subculture from this sector type plaque gives the mixture of a majority of original sector type plaques and several non sector type plaques whenever Sg or PA is used as indicator bacterium.3) Furthermore in the subculture from the latter (non sector type) plaque we can obtain the pure stock of the r type virus which always gives only the r type plaques without any sector on Sg or PA. And this segregant r type virus shows no tendency to revert to the original s type virus.4) Besides the unique pattern of this dissociation phenomenon, it is considered to be very interesting that the occurrence of this specific phenomenon can be detected on indicators Sg and PA but not on PK and Pl.5) Two speculations were put into consideration for the explanation of the genesis of this curious phenomenon.One is the assumption of a mutable gene locus in these s type viruses……(a).Another is that of a partial diploid structure which differs in various points from the so-called residual heterozygote reported by Hershey……(b).(6) Through several recombination analyses we have obtained some experimental data supporting the latter speculation (b). In other words we prefer to consider that these s type viruses have a somewhat heterozygous and partial diploidic structure in their gene constitution.However, we do not want to leave the impression that we insist upon considering speculation (b) as the only possibility. It is our hope that we may someday fully investigate the genesis of this phenomenon through the study of this interesting virus material, e. g., the analysis of the segregant from newly formed sector type virus.