Plasmid DNA in virulent and avirulent gonococci.

The presence of covalently closed circular (CCC) DNA in virulent and avirulent colonial types of Neisseria gonorrhoeae strain 2686, and of type 3 colonies of strain F62 was investigated. CCC DNA was present in each, and the percentage of plasmid relative to total DNA was similar. The percentage of CCC DNA was similar in cells grown on a solid as compared with a liquid medium and in cells grown in the presence of varying concentrations of glucose. No correlation could be established between the presence of plasmid DNA and virulence of N. gonorrhoeae.