Approximate molecular weight of envelope protein 1 and colony opacity of Neisseria gonorrhoeae strains isolated from patients with disseminated or localized infection.

The patterns of electrophoretic (SDS-PAGE) migration of the major outer membrane protein I of 35 strains of Neisseria gonorrhoeae causing disseminated gonococcal infections (DGI) were compared, and the proportion of colonies expressing the transparent phenotype on a solid medium was determined. Thirty-one of these DGI strains had a protein I of very similar apparent molecular weight (approximately 36,000 daltons), and at least 75% of their colonies on a translucid medium expressed the transparent phenotype. Strains responsible for localized infections and isolated from patients in the same geographic area (Montreal) showed a greater heterogeneity in both apparent molecular weight of protein I and colonial opacity than did strains from patients with DGI. In particular, most prototrophic strains obtained from patients with localized infection had proteins I with molecular weights varying from 35,000 to 38,000 daltons and gave predominantly opaque colonies.