title: Insertion of a transposon for chloramphenicol resistance into bacteriophage Mu.
abstract: We have isolated mutants of bacteriophage Mu carrying the X mutations caused by the insertion of cam (Tn9), a transposon for chloramphenicol resistance. The Mu X cam mutants were obtained by selecting for heat-resistant survivors of a Mucts62, P1cam dilysogen. Like the previously described X mutants, Mu X cam mutants are defective prophages which can be excised from the host DNA at a frequency of 10(-5) to 10(-7) per cell. Tn9 insertions in Mu X cam mutants are located within 5000 base pairs of the left end of Mu DNA in a region that controls early replication functions of Mu. There is one EcoRI cleavage site in Tn9. The Tn9 transposon itself can be excised precisely from the Mu X cam mutants to generate wild type Mu. In most Mu X cam mutants, precise excision of Tn9 occurs at a low frequency (10(-6) per cell), whereas in some, the frequency is higher (10(-4) per cell). Mu X cam prophages can replicate after induction with the help of wild type Mu. The lysates containing Mu X cam particles, however, fail to transduce chloramphenicol resistance at a high frequency; Mu X cam mutants apparently have a cis dominant defect in integration.
mesh_terms: D002701:Chloramphenicol; D003090:Coliphages / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D004274:DNA, Recombinant; D004279:DNA, Viral / Q000235:genetics; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000235:genetics; D009154:Mutation; D011815:R Factors; D014161:Transduction, Genetic
chemical_list: D004269:DNA, Bacterial; D004274:DNA, Recombinant; D004279:DNA, Viral; D002701:Chloramphenicol