Nonpilar surface appendages of colony type 1 and colony type 4 gonococci

Abstract

The nature and distribution of surface appendages morphologically distinct from pili were examined in three strains of gonococci. As reported previously by others, large appendages were seen emanating from colony type 1 gonococci when negatively stained preparations were examined by electron microscopy. Whereas the diameter of pili was 4 to 6 nm, the appendages varied from 8 to 40 nm in diameter with bulbous enlargements of up to 130 nm. However, in contrast to previous findings, the appendages were not limited to virulence-associated colonial types but occurred with almost equal frequency on organisms from colonial types 1 and 4. Thus, the presence of these appendages on gonococci was unrelated to colonial morphology, and there is currently no reason to associate them with gonococcal virulence. The large appendages were seldom seen if the organisms were suspended in isotonic fluid rather than in distilled water, which was used in previous studies. This suggests that the large appendages may occur infrequently in the isotonic environment of tissues or in slightly hypertonic purulent exudates. Nevertheless, we did observe small appendages or cell wall blebs on the surface of gonococci suspended in isotonic medium and noted similar structures as spheres free in the surrounding milieu. These findings suggest that the material of which the large appendages consist may form small appendages or cell wall blebs and be shed into the milieu under isotonic conditions. Such cell wall blebs have been demonstrated on meningococci and been shown to consist of endotoxin.