A Study on the Mechanism of DNA Excretion fromP. aeruginosaKYU-1—Effect of Mitomycin C on Extracellular DNA Production—

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Abstract
The mechanism of excretion of DNA was investigated using strain KYU-1. This strain produced a considerable amount of DNA extracellularly (7.8mg/ml), and the amount of extracellular DNA per ml of the culture was scores of times more compared to that of intracellular DNA per ml of the culture. DNA synthesis was repressed by the addition of inhibitors (nalidixic acid, 5-fluoro uracil or mitomycin C), their inhibition rates were 35 to 54%. With the addition of 100 μg/ml of mitomycin C at the middle of the logarithmic growth phase, only 0.89 mg of extracellular DNA per ml of the culture was obtained, the inhibition rate was 95%. However, the amount of organic phosphate synthesized in the culture was almost the same no matter whether with or without an inhibitor. Furthermore, the excretion of DNA from the cell surface of strain KYU-1 was observed with on electron microscope and the DNA molecules excreted were found to be double-stranded.