[Gradual penetration of T7 phage DNA molecules into Escherichia coli cells during infection in the presence of chloramphenicol].

The cell-attached T7 phage DNA has been analyzed when E. coli was infected in the presence of chloramphenicol or rifampicin followed by sonication to provide phage desorption. Sucrose gradient sedimentation of the cell T7-DNA followed by HpaI digestion and agarose gel electrophoresis were performed. The results obtained suggest a gradual entrance of the T7-DNA molecule into the host cell starting on its left end bearing early genes. These data support the conception that the T7-DNA entrance into host cell is directly coupled with its transcription by RNA polymerase. At the same time one more HpaI fragment was found even in the cells, infected with the phage in the process of rifampicin. It may be that this fragment corresponds to the right end of the T7 chromosome, thus suggesting that short fragment of the T7-DNA right end can also enter the host cell early in infection.