Observations on the infection of bacterial protoplasts with the deoxyribonucleic acid of bacteriophage phi X174.

Abstract

An improved procedure for preparation and infection of protoplasts with ΦX DNA, resulting in a higher efficiency of infection and a linear relation between infective centers produced and DNA concentration, is described. The effects of various ionic conditions and of various interfering agents upon this procedure are discussed. Studies of the fate of the viral DNA using this procedure indicate that at least 70% remains free, and largely still potentially infective, while at least 10% attaches to the protoplasts. Most of this attached fraction is, potentially, infective, but only a few molecules per thousand succeed in iniating an infection. Studies of the combined effects of DNA concentration and protoplast concentration reveal that over a wide range of conditions [infected protoplasts] = 10−12 [DNA molecules] [protoplasts] This result is interpreted to mean that the limitations upon infection are primarily kinetic, and do not represent limitations imposed by the proportions of infective DNA or of infectable protoplasts.