A study of the 70 s component of bacteriophage φX174

The 70 s component of bacteriophage φ X174 has been highly purified. The particle and its DNA have been characterized by physical, chemical and biological means and their properties compared with those of the 114 s component of φ X174. 70 s φ X174 and its DNA are biologically inactive. The 70 S φ X174 contains a nucleic acid molecule resembling the DNA of infective 114 s φ X174 but with an average of one-sixth as many nucleotides. The infectious process initiated by the 114 s φ X174 bacteriophage or its DNA differs markedly from that induced by larger bacterial viruses such as those of the T-even series. Specifically, no endolysin production can be detected in infected cells, release of progeny precedes cellular dissolution, and the killing function may reside with DNA rather than with coat protein. These features of φ X174 infection, as well as the production of the incomplete 70 s particles, may be characteristic of a large group of “minimum” or “primitive” viruses which contain a maximum of about 5000 nucleotides in their nucleic acid molecules and are thus able to code fewer than ten new enzymes.