Effects of amino acids on colony phenotype of Neisseria gonorrhoeae.

The effects of amino acid supplementation of commercially available semidefined GC media (Oxoid GC medium and Difco GC base) on the stability of the virulent colony phenotype of Neisseria gonorrhoeae were studied. The -SH-containing amino acids, together with glycine, were found to cause segregation of avirulent colony types followed by growth inhibition after addition of 40 mg/100 ml. Proline and arginine were found to change the colony phenotype profile significantly without reducing the viable count. Arginine supplementation in both media caused a progressive loss of virulent colony types, whereas proline had the opposite effect.