title: Electron microscopic evidence for linear insertion of bacteriophage MU-1 in lysogenic bacteria.
abstract: 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 mum and 53.2 +/- 0.4 mum, respectively. The mean difference, 15.6 mum, is similar to the mean contour length of 12.9 +/- 0.1 mum 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.
mesh_terms: D000225:Adenine / Q000032:analysis; D002499:Centrifugation, Density Gradient; D002586:Cesium; D002712:Chlorides; D003090:Coliphages / Q000254:growth & development / Q000302:isolation & purification; D003227:Conjugation, Genetic; D003596:Cytosine / Q000032:analysis; D004269:DNA, Bacterial / Q000032:analysis / Q000302:isolation & purification; D004279:DNA, Viral / Q000032:analysis / Q000302:isolation & purification; D003903:Deuterium; D004926:Escherichia coli / Q000032:analysis / Q000254:growth & development; D006147:Guanine / Q000032:analysis; D008242:Lysogeny; D008854:Microscopy, Electron; D008970:Molecular Weight; D009154:Mutation; D010087:Oxides; D013431:Sulfates; D013936:Thymidine / Q000032:analysis; D014316:Tritium
chemical_list: D002712:Chlorides; D004269:DNA, Bacterial; D004279:DNA, Viral; D010087:Oxides; D013431:Sulfates; D014316:Tritium; D002586:Cesium; D006147:Guanine; D003596:Cytosine; D003903:Deuterium; D000225:Adenine; D013936:Thymidine