Purified phi 6 nucleocapsids are capable of productive infection of host cells with partially disrupted outer membranes.

Purified nucleocapsids of bacteriophage phi 6, lacking the phage lipid envelope, are unable to infect intact Pseudomonas syringae host cells. A method for studying the process by which a naked virus particle, the phi 6 nucleocapsid, penetrates the host cytoplasmic membrane was developed. Host cells were rendered competent for nucleocapsid infection by treatment with repeated washings with salt and sucrose and the subsequent addition of lysozyme. This treatment disrupts the outer membrane, permitting the nucleocapsid to reach the cytoplasmic membrane and to infect the cell. The nucleocapsid infection is blocked by monoclonal antibodies raised against the nucleocapsid shell protein P8.