Inhibition of coliphage multiplication and R plasmid transfer by desdanine.

Desdanine inhibited the plaque formation of male-specific coliphages but not that of other coliphages tested. Desdanine also suppressed the multiplication of both RNA phage Q beta and filamentous DNA phage f1 at the concentration of 3.13 approximately 6.25 mug/ml which had no influence on the growth of their host cells. However, the inhibitory effect on the phage multiplication was not due to the inactivation of phage particles nor the prevention of phage adsorption and penetration into the host cells. Desdanine also inhibited the transfer of R plasmid, R 100-1, in E. coli at 6.25 approximately 12.5 mug/ml without affecting the viability of donor and recipient cells.