[Various properties of virulent and moderate Erwinia carotovora phages]

A bacterial culture of E. carotovora 8638 lysed by virulent phage 62 after treatment with UV rays produces a moderate phage. The virulent and moderate viruses, antigenically unrealted, have a similar prolonged latent period (100 min) and the period of lysis (60 min). They also differ in the sizes of the capsids and the length of processes which are 750+/-30 and 2000+/-50A in the virulent phage and 600+/-30 and 1500+/-50A, in the moderate phage, respectively. The sedimentation constants are 602 and 340 S, respectively. In the virulent virus, the volume of the cavity of the protein capsid contianing 8 major and 5 minor peptides is twice as large as that in the moderate one (with 8 peptides); the molecular weight of their DNA shows approximately similar ratios: 52.53+/-17X10(6) and 29.79+/-0.88X10(6) daltons. Evidently, the moderate phage because of the reduced size of the genome contains less message for coding for structural proteins and nucleoprotein as a whole.