Effects of genome size on bacteriophage phi X174 DNA packaging in vitro.

Effects of the size of template DNA on the DNA packaging reaction of bacteriophage phi X174 were studied using plasmids of various sizes which contain the phi X174 origin of DNA replication and the in vitro phage synthesizing system (Aoyama, A., Hamatake, R. K., and Hayashi, M. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 4195-4199). DNA between 78.5% and 101% of the length of phi X174 DNA produced infectious particles efficiently. Packaging of DNA smaller or larger than this range produced uninfectious defective particles. Although these particles contained circular single-stranded DNA, they suffered structural changes which altered the sedimentation properties or the ability to adsorb to the cells. Mutant phage were found from the packaging reaction of DNA larger than 101% of phi X174 DNA. These mutants deleted the termination region of DNA, suggesting that they were produced by early termination of the phage synthesizing reaction.