Virus Strains of Identical Phenotype but Different Genotype

Abstract

After mixed infection of a culture of the B strain of Escherichia coli with bacterial viruses T2 and T4, a 3d type of virus different from the 2 original parent strains was found in the culture after incubation. This 3d type is phenotypically like T4, being capable of multiplying in the strain B/2, but is genotypically like T2, being no longer capable of growing in the strain B/2 after one passage through it, and thereafter capable of growing in the strain B/4. From the extent of appearance of the "latent T2" virus in the cultures in which it shows its properties, the authors calculate that its concn. in the lysate of the original culture should be about 10% of the concn. of T2. Auxiliary expts. rule out the alternative explanations that the lysate contains aggregates of virus particles formed by a T2 and a T4 particle, or that the observations may result from independent infection of one bacterium by more than 1 virus particle. It was also shown that the phenomenon does not result if in place of the lysate a mixture of T2 and T4 is used.