Conditions required for the attainment of colony-type stability of Neisseria gonorrhoeae in liquid culture.

Colony-type morphology in Neisseria gonorrhoeae is associated with virulence, transformability, and the presence or absence of pili. A reliable method for achieving large populations of cells that are relatively stable with respect to colony type would be valuable, for example, in studies of virulence or for the isolation of pilus-specific phages. Previously described methods designed to achieve type stability in liquid culture were inadequate for a variety of reasons, including their low final cell yields and/or their requirements for prolonged incubation. The success of the procedure described in this communication depends upon the use of an overnight plate harvest to insure a relatively large and stable inoculum for the liquid medium. Yields of as high as 10(10) colony-forming units/ml are routinely obtained after 4 to 5 h of incubation. Such cultures exhibit a colonial-type stability of 85 to 95% with respect to the original colonial type used for inoculation of the start plate.