Molecular and Biological Analysis of Eight Genetic Islands That Distinguish Neisseria meningitidis from the Closely Related Pathogen Neisseria gonorrhoeae

Abstract

The pathogenic species Neisseria meningitidis and Neisseria gonorrhoeae cause dramatically different diseases despite strong relatedness at the genetic and biochemical levels. N. meningitidis can cross the blood-brain barrier to cause meningitis and has a propensity for toxic septicemia unlike N. gonorrhoeae. We previously used subtractive hybridization to identify DNA sequences which might encode functions specific to bacteremia and invasion of the meninges because they are specific to N. meningitidis and absent from N. gonorrhoeae. In this report we show that these sequences mark eight genetic islands that range in size from 1.8 to 40 kb and whose chromosomal location is constant. Five of these genetic islands were conserved within a representative set of strains and/or carried genes with homologies to known virulence factors in other species. These were deleted, and the mutants were tested for correlates of virulence in vitro and in vivo. This strategy identified one island, region 8, which is needed to induce bacteremia in an infant rat model of meningococcal infection. Region 8 encodes a putative siderophore receptor and a disulfide oxidoreductase. None of the deleted mutants was modified in its resistance to the bactericidal effect of serum. Neither were the mutant strains altered in their ability to interact with endothelial cells, suggesting that such interactions are not encoded by large genetic islands in N. meningitidis.Neisseria meningitidis colonizes the nasopharynx, from which it can seed the bloodstream before crossing the blood-brain barrier (BBB) to cause meningitis. In contrast, Neisseria gonorrhoeae colonizes and invades the epithelium of the genitourinary tract, where it can cause a localized inflammation; bacteremia, though frequent, is asymptomatic and dissemination is rare. Thus, both species are capable of crossing a cellular barrier at their port-of-entry but they differ in their abilities to subsequently disseminate in the blood. The ability to induce intense and prolonged bacteremia is one of the prerequisites for a bacterial pathogen to cross the BBB. In contrast, the details of specific interactions with the cellular components of the BBB remain unclear. Therefore, in order to understand the mechanisms that allow N. meningitidis to cross the BBB, it will be necessary to identify the genes that are involved in bloodstream dissemination and/or specific interaction with the cellular components of the BBB. Such genes might be present in both N. meningitidis and N. gonorrhoeae but differ subtly in sequence or regulation, or they might be present in only one of the two species.Results from in vitro models have shown that most of the mechanisms mediating cellular interactions are common to both N. meningitidis and N. gonorrhoeae. On the other hand, several determinants have been identified that are specific to N. meningitidis: the polysaccharide capsule (8), the enzyme rotamase (26), the RTX toxin-like Frp proteins (29, 30), and a glutathione peroxidase (20). Of these, the capsule locus is ...

Genome Analysis and Strain Comparison of Correia Repeats and Correia Repeat-Enclosed Elements in Pathogenic Neisseria

“…Whole genome sequence comparison showed that 91.2% of the 2,158 ORFs of N. meningitidis MC58 are similar to the ORFs of N. meningitidis Z2491 (49). There is no doubt that differences in the genes or ORFs (31,42,50) are important in determining the pathogenic differences between different Neisseria strains. However, the question is whether the distinctive pathogenic behaviors of different pathogens can be completely explained by these differences in the genes or ORFs.…”

Neisserial TonB-dependent outer-membrane proteins: detection, regulation and distribution of three putative candidates identified from the genome sequences The GenBank accession number for the sequence of tdfH from meningococcal strain IR1074 reported in this paper is AF227418.

“…No homologue for NMB1829 was present in meningococcal strain Z2491, whereas a predicted coding sequence (co-ordinates 79 794-80 334) that contained a frame-shift mutation and homology to the C-terminal region part of NMB1829 was present in the FA1090 genome database. Conversely, no homologue for NMA2193\NMB0293 (Klee et al, 2000) or NMA1558 was present in the FA1090 gonococcal genome database. Two probable pseudogenes (NMA1663-1662\NMB1449 and NMB 1346), which encode TonB-dependent proteins with homology to siderophore receptors, were also found in the genome databases of meningococcal strains Z2491 and MC58.…”

The REP2 Repeats of the Genome ofNeisseria meningitidisAre Associated with Genes Coordinately Regulated during Bacterial Cell Interaction

“…mycin resistance cassette into an appropriate restriction site (12). Confirmation of the mutation was performed using PCR and Southern blotting.…”