Piliation and colonial morphology among laboratory strains of meningococci

Abstract

Colonial morphology and piliation were studied on 12 strains from various serogroups of Neisseria meningitidis. Six different colony types (M1 to M6) were identified. Most strains elaborated only an M1 colonial type, which is similar to gonococcus T4. Several combinations of piliation and colonial morphology were observed: colonial variation in which neither parent nor variant were piliated; colonial variation involving piliated and nonpiliated cells; dissociation of piliated from nonpiliated cells with no colonial change; and colonial variation in which both variants were piliated but with distinctly different pili. Correlations between piliation and colony morphology within N. meningitidis are exceptions rather than the rule.