Genetic basis for colonial variation in Neisseria gonorrhoeae

Abstract

When the piliated colony types of Neisseria gonorrhoeae, which predominate in recent isolates, were nonselectively subcultured in vitro, they gave rise to large numbers of nonpiliated, avirulent colonial variants. Evidence is presented to show that most of this variation occurs after active growth has ceased and that the variation is sensitive to the action of deoxyribonuclease. We suggest that this variation is a result of transformation. A second variation in colonial morphology involved differing levels of "colony opacity-associated proteins" in the outer membrane. This variation was also inhibited by the presence of deoxyribonuclease, but the genetic basis for it is not as yet clear.It now seems to be firmly established that there is a strong correlation between the degree of virulence a particular strain of Neisseria gonorrhoeae displays in vivo and its colonial morphology. The Ti and T2 colony types, which predominate in recent isolates, appear to be virulent in both human volunteers and various animal models. On nonselective subculture these strains give rise to large numbers of T3 or T4 colonies, which are relatively avirulent (2, 9).

Novel determinant (comA) essential for natural transformation competence in Neisseria gonorrhoeae and the effect of a comA defect on pilin variation

“…Previous work from several laboratories suggested a role for natural transformation competence in the genetic variability of PitE expression observed in N. gonorrhoeae (Norlander et al. 1979;Seifert et al, 1988, Gibbs et ai.. 1989)-In contrast, it was also shown that p//E variation readily occurred under conditions preventing DNA transformation, i.e.…”

Mosaic-like organization of IgA protease genes in Neisseria gonorrhoeae generated by horizontal genetic exchange in vivo.

“…Owing to these properties, transformation has been invoked as a mechanism involved in pilus-specific colony variation of gonococci (Norlander et al, 1979). Conclusive evidence for the transformation model was recently provided by demonstrating a decreased frequency of pilus phase transitions in a DNA uptake deficient mutant and by growth of gonococci in the presence of DNase I Gibbs et al, 1989).…”

A peptidoglycan hydrolase similar to bacteriophage endolysins acts as an autolysin in Neisseria gonorrhoeae

“…Autolysis and PG hydrolysis in N. gonorrhoeae are not only interesting from the point of view of bacterial physiology but may also be involved in genetic transformation and pathogenesis. Gonococci undergo natural transformation (Sparling, 1966), and the donor DNA is thought to be provided by lysed cells (Norlander et al, 1979;Seifert et al, 1988). Gonococci also release monomeric fragments of PG (Sinha and Rosenthal, 1980) that have multiple biological activities, including killing ciliated fallopian tube cells in the organ culture model of PID (Melly et al, 1984;Fleming et al, 1986;Krueger et al, 1987;Dokter et al, 1994).…”