Relation of protein I and colony opacity to serum killing of Neisseria gonorrhoeae.

Serum bactericidal tests were done for isogenic Neisseria gonorrhoeae that formed transparent or opaque colonies. Analysis of the data from individual strains showed that the molecular weight of protein I was a highly significant, but not universal, determinant of serum sensitivity or resistance. N. gonorrhoeae organisms with high-molecular-weight protein I were more serum-sensitive. Multivariate analysis of the data from 43 strains indicated that N. gonorrhoeae organisms from transparent colonies were more serum-resistant than isogenic organisms from opaque colonies (P = 0.01). Survivors of bactericidal reactions in which the initial inoculum was from opaque colonies tended to form transparent colonies. Bactericidal action by sera from men was highly associated (P less than 0.02) with the molecular weight of protein I and with the presence of protein II bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, whereas bactericidal action by sera from women was associated only with the molecular weight of protein I.