Pyomelanin production by Pseudomonas aeruginosa. I. Transformation of pyomelanin productivity.

Pseudomonas aeruginosa was successfully transformed from a pyomelanin-producing strain to a non-pyomelanin-producing strain by genetic transformation, with an average frequency of 1.17 X 10-3/recipient. Although the transformation frequency was not affected by doses of DNA between 17 and 51 microgram/ml, it was influenced by the growth phase of the recipient bacteria, i.e., it was highest in the late logarithmic phase. Biochemical functions of the transformants were the same as those of the recipient strain except for pyomelanin production. Some of them, however, showed an intermediate growth behavior and cell arrangement between the donor and recipient. The serological type of the donor strain was sometimes contransduced although a few transformants became nonagglutinable with either donor or recipient type antiserum. The pyomelanin producing activity and serological type gained of some transformants were eliminated by either subculturing in nutrient broth or acridine treatment. The results obtained suggested that the pyomelanin productivity of P. aeruginosa is controlled by a plasmid.