Capsule switching of Neisseria meningitidis - PubMed (original) (raw)

Molecular analysis of capsule biosynthesis and membrane transport genes in prototype isolates of serogroup A, B, C, Y, and W-135 N. meningitidis. (A) Genetic basis for serogroup B meningococcal capsular polysaccharide. Meningococcal capsules are produced by genes encoded by the 24-kb cps gene complex (19), which is composed of five regions: E, C, A, D, and B. In serogroup B, four capsular biosynthetic genes (synX–D) are found in region A and are transcribed as an operon. Region C, adjacent to region A, contains four polycistronic genes, ctrA–D, encoding proteins that transport the phospholipid-substituted polysialic acid across the inner and outer membranes. The ctr genes are transcribed in the opposite orientation from the syn biosynthetic genes of region A, but use the same 134 bp promoter region (26). (B) The biosynthetic pathway for production of serogroup B capsule; SynX is either the _N_-acetyl-

-glucosamine-6-phosphate 2-epimerase that produces _N_-acetyl-

-mannosamine 6-phosphate or a specific phosphatase that converts _N_-acetyl-

-mannosamine 6-phosphate into _N-_acetyl-

-mannosamine (21); SynB is the CMP-_N-_acetylneuraminic acid (NANA) synthetase (23); SynC is the NANA synthetase (22); and SynD is the polysialyltransferase responsible for (α2→8)-linked polysialic acid chain polymerization and elongation (24). (C) Southern DNA hybridization showing ctrA homology in serogroups A (strains F8229, F8239), B (strains NMB, 1070 [B-301*]), C (strains FAM18, 1205 [C-301*], 1843 [C-301]), Y (strain GA0929), and W-135 (strain 6083) of N. meningitidis. Chromosomal DNA from each of the strains was prepared, digested with _Cla_I, electrophoresed through a 1.2% agarose gel, and transferred to a nylon membrane. The membrane was then probed with a 150 bp digoxigenin-labeled PCR product derived from the 5′-end of the serogroup B ctrA gene. N. lactamica and N. gonorrhoeae (GC) showed no hybridization. Molecular weight size standards (Boehringer Mannheim) flank the chromosomal digests. (D) PCR amplification of ctrA and synX–synD from serogroups A (strain F8239), B (strain NMB), C (strain FAM18), W-135 (strain 6083), and Y (strain GA0929) N. meningitidis using oligonucleotide primers derived from the individual gene sequences of serogroup B prototype strain NMB. Kb DNA ladders (BRL) flank the gel. [Fig. 1 A and B are modified with permission from ref. (Copyright 1996, American Society for Microbiology).]