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Electron Microscopic Evidence for Linear Insertion of Bacteriophage MU-1 in Lysogenic Bacteria

1971; American Society for Microbiology; Volume: 8; Issue: 4 Linguagem: Inglês

10.1128/jvi.8.4.551-563.1971

1098-5514

Jaime Martuscelli, Austin L. Taylor, Donald J. Cummings, V. A. Chapman, S. S. DeLong, Leonardo Fernandes Canedo,

Bacterial Genetics and Biotechnology

Temperate bacteriophage Mu-1 was used to generate a lysogenic derivative of the F′ lac episome of Escherichia coli . Intact, covalently circular molecules of F′ lac and lysogenic F′ lac Mu + deoxyribonucleic acid (DNA) were isolated and examined by electron microscopy. The mean contour lengths of F′ lac and F′ lac Mu + molecules were 37.6 ± 0.4 μm and 53.2 ± 0.4 μm, respectively. The mean difference, 15.6 μm, is similar to the mean contour length of 12.9 ± 0.1 μm obtained for linear DNA molecules released by osmotic shock from mature phage Mu-1 virions. These results provide direct physical evidence that phage Mu-1 integrates by linear insertion of its genome into the DNA of lysogenic host bacteria. Chemical and physical analyses of phage Mu-1 DNA indicate that it is similar to E. coli DNA in respect of gross base composition, buoyant density, and melting temperature.