Characterization of genomic DNA of mycobacteriophage I3

The GC content of mycobacteriophage I3 DNA is 67% as determined from thermal melting analysis, buoyant density in CsCl gradient, and 5-deoxymononucleotide analysis. High-resolution melting of I3 DNA revealed that the base distribution is random. Studies with methylation-specific restriction enzymes and high voltage electrophoretic analysis of 5-deoxymononucleotides did not indicate the presence of any unusual or methylated bases in I3 DNA. The molecular size of I3 DNA is estimated to be about 135 Kbp, based on the restriction fragment size distributions and sedimentation in sucrose gradients. The restriction cleavage pattern by a variety of restriction endonucleases has been determined. The circularly permuted nature of I3 DNA, indicated from the restriction patterns, has been confirmed by Southern blot hybridizations and 5 end group analysis.