BACTERIOPHAGE MU-1 - TOOL TO TRANSPOSE AND TO LOCALIZE BACTERIAL GENES

By mating either induced F'' strains (which carry a thermoinducible Mu prophage in the bacterial chromosome) or sensitive F'' infected with Mu, with appropriate recipients, new F'' episomes were isolated which carried various lengths of bacterial [Escherichia coli] DNA. The transposition frequency of a given marker may be as high as 10-4. The episomes which carried the transposed DNA always carried Mu as well. Since induction or infection with Mu was necessary for transposition to occur, Mu enzymes and Mu DNA were probably required by the transposition process. Episomes selected for the presence of a given marker were analyzed for the presence of unselected markers. Only the markers linked to the selected marker were cotransposed with it. When 2 markers were simultaneously transposed, all markers lying between them on the chromosome were also transposed. The cotransposition frequency of an unselected marker was somehow related to the distance between that marker and the selected marker. The transposition process occurred in Rec+ and Rec- strains. Mu-mediated transposition offered a new way to isolate F episomes and to localize and order bacterial genes as far apart as 3 min.