Induction and reversion of the L-form of Neisseria gonorrhoeae

Massive induction of Neisseria gonorrhoeae to the L-form was achieved on L-media consisting of brain heart infusion broth, 1% agar, 10% horse serum, and 100 units per milliliter penicillin. This medium was supplemented with polyvinylpyrrolidone (PVP) for stabilization. Frequencies greater than 10% were routinely found with all 11 strains tested. Five of the 11 strains were also transformed to the L-form on L-media supplemented with 10% sucrose but at efficiencies much lower than on PVP L-media. Rare L-colonies (less than 1 in 107 gonococci) of these same five strains were also isolated on unstabilized L-media. No L-forms were ever isolated from the remaining six strains on sucrose or on unstabilized L-media. The penicillin concentration in the media, if above a lethal amount, had little effect on the efficiency of L-phase induction on PVP L-media but was critical for isolation on sucrose L-media. Colonial growth of the L-form was much more rapid and luxuriant on PVP than on sucrose L-media. In addition, subculture by the agar-block technique of L-phase colonies induced on PVP L-media routinely occurred while growth was seldom obtained on subculture from sucrose L-media. Reversion to the gonococcal parent occurred (1) on transfer of growth by the agar-block technique to similar media without penicillin or to Mueller Hinton blood agar, (2) in L-broth into which an agar block containing L-colonies was placed and time allowed for decay of penicillin, (3) on sucrose but not PVP L-media, within the original transformed L-colonies after penicillin decay. Growth in PVP L-broth was achieved. On transfer from broth culture to growth media without penicillin, reversion to the parental gonococci occurred.