Colony variants of Neisseria meningitidis strain 2996 (B:2b:P1.2): influence of class-5 outer membrane proteins and lipopolysaccharides.

Different colonial morphologies were found among colonies of Neisseria meningitidis strain 2996 (B:2b:P1.2). Examination of cultures, selected on the basis of colony transparency or opacity, revealed that both lipopolysaccharides (LPS) and class-5 outer membrane proteins (OMP) are associated with differences in colonial morphology. Among 13 variants, four LPS variants and two class-5 OMP variants were recognised. All variants were non-fimbriate. The LPS variations were confirmed by immunoprecipitation. In addition to these qualitative variations of LPS, meningococci synthesise LPS of different molecular size depending upon growth phase; larger LPS molecules were found after analysis of stationary-phase cultures than with exponential-phase cultures. These changes did not cause a change in serotyping characteristics. The recognition in this study of intra-strain heterogeneity of meningococcal LPS and class-5 OMPs is important for the understanding of meningococcal pathogenicity. This heterogeneity was also detected in simultaneous isolates from different sites of a patient.