Deletions in Klebsiella pneumoniae R plasmids induced by growth in the presence of acridine orange at high temperature.

The generation in vivo of plasmids deleted at specific sites in strains of Klebsiella pneumoniae containing R plasmids, by treatment with high concentrations of acridine orange (1.2 mg/ml) at 42 degrees C are reported. These deletions seem to be site specific because loss of specific restriction fragments after digestion with restriction enzymes was demonstrated.