Molecular divergence of the sia locus in different serogroups of Neisseria meningitidis expressing polysialic acid capsules |
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| Authors: | H Claus U Vogel M Mühlenhoff R Gerardy-Schahn M Frosch |
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| Institution: | Institut für Hygiene und Mikrobiologie, Universit?t Würzburg, Josef-Schneider-Str. 2, 97080 Würzburg, Germany Fax +931 201-3445; e-mail: mfrosch@hygiene-uni-wuerzburg.de, DE
Institut für Medizinische Mikrobiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany, DE
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| Abstract: | The serogroups B, C, W135 and Y of Neisseria meningitidis express chemically and immunologically distinct capsular polysaccharides containing sialic acid. In the case of serogroup B meningococci sialic acid is synthesized by the gene products of a locus termed sia and forms the homopolymers of the capsule. The organization of the genes required for sialic acid synthesis in serogroups B, C, W135 and Y was elucidated by PCR technology. Cloning, sequencing and the functional expression of the polysialyltransferase (PST) genes of serogroups B and C demonstrated that the difference in capsule composition derives from the presence of related, but distinct siaD genes coding for PSTs. Analysis of meningococci of serogroups W135 and Y expressing sialic acid heteropolymers revealed that the DNA sequences of the corresponding genetic loci in these serogroups were highly homologous, but differed completely from the siaD genes of serogroups B and C. This finding suggests that enzymes unrelated to those of serogroups B and C are required for the formation of sialic acid heteropolymers characteristic of the capsules of serogroups W135 and Y. |
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