[Development of bacteriophage Mu in E. coli gyrBts mutant strain]

The study deals with Mu growth in cells carrying a temperature-sensitive mutation in the gene of DNA gyrase B subunit. At a nonpermissive temperature the Mu growth is shown to be blocked in the host gyrB ts mutant both on infection and on prophage induction. Mu DNA does not get integrated in the host chromosome upon the infection of mutant cells, as demonstrated by DNA-DNA hybridization experiments. In the case of prophage induction in mutant cells, as opposed to the wild type cells early mRNA synthesis is practically fully inhibited while the total RNA synthesis is three times reduced after 20 min of induction. The transcription of phage DNA associated with the changed superhelicity of DNA in the cell.