Characterization and comparison of the DNAs of the three closely related bacteriophages gd, ge and gf with the genome DNA of the hydrogen-oxidizing host strain <em>Pseudomonas pseudoflava</em> GA3.

The double-stranded (ds)DNAs of the three closely related temperate Pseudomonas pseudoflava bacteriophages gd, ge and gf were studied biochemically and biophysically. The GC content of the DNA was 67.4 &plusmn; 0.5% and differed only slightly from that of the host P. pseudoflava. By electron microscopic length measurements a mol. wt. of 26.1 x 106 to 26.7 x 106 was calculated for the three bacteriophage DNAs. Homogeneity of the bacteriophage DNAs was further demonstrated by specific cleavage with restriction endonucleases EcoRI and HindIII. It was concluded that the three homo-immune bacteriophages are identical. The genome size of the host P. pseudoflava GA3 was 3.7 x 109 as calculated from optical renaturation rate measurements with Xanthomonas pelargonii reference DNA. The bacteriophage gd genome thus amounts to 0.7% of the chromosome of this bacterial host