Evidence for a common molecular origin of the capsule gene loci in Gram‐negative bacteria expressing group II capsular polysaccharides

Abstract

Capsular polysaccharides of Gram-negative bacteria contribute to a large extent to the pathogenicity of these organisms. We show here that the molecular organization of the capsule gene loci in different serogroups of Neisseria meningitidis is similar to that of Haemophilus influenzae and Escherichia coli. A common molecular origin of the mechanisms of encapsulation is indicated by strong homology of the genes involved in transport of the capsular polysaccharides to the cell surface in all these organisms. The proteins involved in capsular polysaccharide transport fit the characteristics of ABC (ATP-binding cassette) transporters. Furthermore, by sequence comparison of the sialytransferases of N. meningitidis B and E. coli K1, the capsule of which is composed of alpha 2,8-linked polyneuraminic acid, a significant degree of homology was observed, indicating that the capsular polysaccharide type itself has the same evolutionary origin in these two pathogens.

A new subfamily of bacterial ABC‐type transport systems catalyzing export of drugs and carbohydrates

“…The consensus sequence is provided below the multiple alignment, and residues conserved in all five proteins are indicated by an exclamation mark above the multiple alignment. In addition to the DrrB protein of S. peucetius (Sp) (Guilfoile & Hutchinson, 1991), these proteins include the BexB protein of the polyribosylribitol phosphate capsular polysaccharide export system of Haemophilus influenzae (Hi) (Kroll et al, 1988, the CtrC protein of the polyneuraminic acid capsular polysaccharide export system of Neisseria meningitidi3 (Nm) (Frosch et al, 1991), the KpsM protein of the polyneuraminic acid capsular polysaccharide export system of Escherichia coli (Ec) (Smith et al, 1990;Pavelka et al, 1991), and the NodJ protein of R. leguminosarum (RI) (Evans & Downie, 1986). Table 1 summarizes the binary comparison scores (in standard deviations) for these five proteins.…”

Down‐regulation of pili and capsule of Neisseria meningitidis upon contact with epithelial cells is mediated by CrgA regulatory protein

“…sia operon contains four genes, siaABCD, that are involved in the capsule biosynthesis. The sia operon is divergently transcribed from the capsule transport operon ctrABCD (Frosch et al, 1991;Tzeng et al, 2001). The effects of CrgA on this UTR and on the expression of the divergent ctr operon remain to be tested.…”

Comparative analysis of the genome sequences of Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica

“…Several references to a Bordetella capsule have been made in the literature 36,37 , but it is not clear what structure is being referred to, and a capsule has not been isolated and characterized from the bordetellae. The locus arrangement for the Bordetella capsule is typical of that of type II capsules 38 , comprising three regions involved in export/modification, biosynthesis and transport. The genes involved in biosynthesis of the Bordetella capsule encode products that are homologous to the Salmonella typhi Vi antigen biosynthesis enzymes, suggesting that the product of the Bordetella locus may be similar to the N-acetyl galactosaminuronic acid Vi antigen polymer.…”