Prevalence and Detailed Mapping of the Gonococcal Genetic Island in Neisseria meningitidis (original) (raw)
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Complete and variant forms of the 'gonococcal genetic island' in Neisseria meningitidis
Microbiology, 2005
Comparative genome hybridization using the pan-Neisseria microarray identified genes from the gonococcal genetic island (GGI) within Neisseria meningitidis strains of serogroups W-135, H, and Z. While some of these strains contain nearly all of the genes of the GGI, there are differences in the presence of some of these genes between the strains, including between those of the same serogroup. Attempts were then made to determine the location of the GGI in these meningococci. Sequencing of Neisseria gonorrhoeae strain MS11 revealed that the GGI is a conjugative plasmid that can be chromosomally integrated at the dif sites near ung and can also be present in its circularized form. In N. meningitidis, a dif site is present in this location and also serves as the point of chromosomal integration of the GGI in this species.
Many carried meningococci lack the genes required for capsule synthesis and transport
Microbiology (Reading, England), 2002
Of 830 Neisseria meningitidis isolates obtained from healthy carriers in Bavaria, Germany, 136 (16.4%) lacked the operons necessary for the synthesis, lipid modification, and transport of capsular polysaccharide. These operons were replaced by a non-coding intergenic region either 113 or 114 bp in length, termed here the capsule null locus (cnl). Comparisons of the nucleotide sequence of this region in the meningococcus and its acapsulate relatives, Neisseria gonorrhoeae and Neisseria lactamica, revealed six distinct sequence variants (cnl-1 to cnl-6), with a total of 10 nucleotide substitutions and three indels. With the exception of one 4 bp insertion, which was unique to a gonococcal isolate, all of the individual sequence changes were present in the N. lactamica isolates examined. The meningococcal isolates with a cnl belonged to one of four otherwise genetically diverse genetic groupings: the ST-53 and ST-1117 complexes (75 isolates); the ST-845 complex (12 isolates); the ST-19...
Identification and Characterization of Genes Required for Competence in Neisseria meningitidis
Journal of Bacteriology, 2005
We have identified genes required for competence of Neisseria meningitidis, a naturally transformable human pathogen. Although not comprehensive, our analysis identified competence-defective mutants with transposon insertions in genes not previously implicated in this process in Neisseria. Neisseria meningitidis is a human pathogen that colonizes the nasopharynx (5, 11, 27) but also causes septicemia and meningitis (33). The bacterium is naturally transformable, providing a mechanism for genetic heterogeneity (4, 11, 21, 42). For example, N. meningitidis sodA has been acquired from Haemophilus influenzae (18), and genes encoding housekeeping functions and targets of the immune response have a mosaic structure (9, 10, 29, 37, 38). Transformation involves multiple steps, including DNA uptake, processing, and chromosomal integration (19). The basis of transformation in Neisseria gonorrhoeae has been intensively studied (16, 17). Uptake of genus-specific DNA (8, 13) is mediated by type IV pili (Tfp) at the bacterial surface. Next, incoming DNA is converted, in part, to a single-stranded intermediate (6), while the subsequent events are not well defined. Little is known about transformation in N. meningitidis (1), although it expresses one of two types of Tfp, with only class I (differentiated from class II pili by binding of the monoclonal antibody SM1) conferring competence (24). We describe the use of signature-tagged mutagenesis (STM) to identify genes required for meningococcal competence (14). The bacterial strains and plasmids used are shown in Table 1, and growth conditions and antibiotics are described elsewhere (32). A recA mutant was constructed as a strain defective for homologous recombination. Primers NG102 (5Ј-ATC GCTCGGATTAGACCTC-3Ј) and NG103 (5Ј-ATGTCGAT CAATTCGCC-3Ј) amplified a 702-bp recA product, which was ligated into pCR2.1 TOPO; inverse PCR with oligonucleotides NG106 (5Ј-GTCACGCGTACTACCATATCTATG-3Ј) and NG107 (5Ј-GTCACGCGTTGAGCCAGGCTTTGC-3Ј) introduced a deletion and a MluI site (underlined) into the plasmid into which a kanamycin resistance gene was inserted. Plasmids containing an inactivated pilE allele (as a strain defective for DNA uptake) were obtained by in vitro mutagenesis. pilE was amplified using PilE1 (5Ј-TTTACCCTTATCGA GCTGATG-3Ј) and PilE2 (5Ј-TTAGCTGGCATCACTTGC
Microbiology-sgm, 2006
To better understand Neisseria meningitidis genomes and virulence, microarray comparative genome hybridization (mCGH) data were collected from one Neisseria cinerea, two Neisseria lactamica, two Neisseria gonorrhoeae and 48 Neisseria meningitidis isolates. For N. meningitidis, these isolates are from diverse clonal complexes, invasive and carriage strains, and all major serogroups. The microarray platform represented N. meningitidis strains MC58, Z2491 and FAM18, and N. gonorrhoeae FA1090. By comparing hybridization data to genome sequences, the core N. meningitidis genome and insertions/deletions (e.g. capsule locus, type I secretion system) related to pathogenicity were identified, including further characterization of the capsule locus, bioinformatics analysis of a type I secretion system, and identification of some metabolic pathways associated with intracellular survival in pathogens. Hybridization data clustered meningococcal isolates from similar clonal complexes that were distinguished by the differential presence of six distinct islands of horizontal transfer. Several of these islands contained prophage or other mobile elements, including a novel prophage and a transposon carrying portions of a type I secretion system. Acquisition of some genetic islands appears to have occurred in multiple lineages, including transfer between N. lactamica and N. meningitidis. However, island acquisition occurs infrequently, such that the genomic-level relationship is not obscured within clonal complexes. The N. meningitidis genome is characterized by the horizontal acquisition of multiple genetic islands; the study of these islands reveals important sets of genes varying between isolates and likely to be related to pathogenicity.
Evolutionary and genomic insights into meningococcal biology
Future Microbiology, 2012
Epidemic disease caused by Neisseria meningitidis, the meningococcus, has been recognised for two centuries, but remains incompletely controlled and understood. There have been dramatic reductions in serogroup A and C meningococcal disease following the introduction of proteinpolysaccharide conjugate vaccines but there is currently no comprehensive vaccine against serogroup B meningococci. Genetic analyses of meningococcal populations have provided many insights into the biology, evolution, and pathogenesis of this important pathogen. The meningococcus, and its close relative the gonococcus, are the only pathogenic members of the genus Neisseria, and the invasive propensity of meningococci varies widely, with around a dozen 'hyper invasive lineages' responsible for most disease. Despite this, attempts to identify a 'pathogenome', a subset of genes associated with the invasive phenotypes have failed; however, genome-wide studies of representative meningococcal isolates using high throughput sequencing are beginning to provide detail on the relationship of invasive phenotype and genotype in this fascinating organism and how this relationship has evolved.
Infection and Immunity, 2005
Proteins secreted by Neisseria meningitidis are thought to play important roles in the pathogenesis of meningococcal disease. These proteins include the iron-repressible repeat-in-toxin (RTX) exoprotein FrpC. Related proteins in other pathogens are secreted via a type I secretion system (TOSS), but such a system has not been demonstrated in N. meningitidis. An in silico search of the group B meningococcal genome suggested the presence of a uniquely organized TOSS. Genes encoding homologs of the Escherichia coli HlyB (ATPbinding), HlyD (membrane fusion), and TolC (outer membrane channel) proteins were identified. In contrast to the cistronic organization of the secretion genes in most other rtx operons, the hlyD and tolC genes were adjacent but unlinked to hlyB; neither locus was part of an operon containing genes encoding putative TOSS substrates. Both loci were flanked by genes normally associated with mobile genetic elements. The three genes were shown to be expressed independently. Mutation at either locus resulted in an inability to secrete FrpC and a related protein, here called FrpC2. Successful complementation of these mutations at an ectopic site confirmed the observed phenotypes were caused by loss of function of the putative TOSS genes. We show that genes scattered in the meningococcal genome encode a functional TOSS required for secretion of the meningococcal RTX proteins.
PLoS Genetics, 2007
The bacterium Neisseria meningitidis is commonly found harmlessly colonising the mucosal surfaces of the human nasopharynx. Occasionally strains can invade host tissues causing septicaemia and meningitis, making the bacterium a major cause of morbidity and mortality in both the developed and developing world. The species is known to be diverse in many ways, as a product of its natural transformability and of a range of recombination and mutation-based systems. Previous work on pathogenic Neisseria has identified several mechanisms for the generation of diversity of surface structures, including phase variation based on slippage-like mechanisms and sequence conversion of expressed genes using information from silent loci. Comparison of the genome sequences of two N. meningitidis strains, serogroup B MC58 and serogroup A Z2491, suggested further mechanisms of variation, including C-terminal exchange in specific genes and enhanced localised recombination and variation related to repeat arrays. We have sequenced the genome of N. meningitidis strain FAM18, a representative of the ST-11/ET-37 complex, providing the first genome sequence for the disease-causing serogroup C meningococci; it has 1,976 predicted genes, of which 60 do not have orthologues in the previously sequenced serogroup A or B strains. Through genome comparison with Z2491 and MC58 we have further characterised specific mechanisms of genetic variation in N. meningitidis, describing specialised loci for generation of cell surface protein variants and measuring the association between noncoding repeat arrays and sequence variation in flanking genes. Here we provide a detailed view of novel genetic diversification mechanisms in N. meningitidis. Our analysis provides evidence for the hypothesis that the noncoding repeat arrays in neisserial genomes (neisserial intergenic mosaic elements) provide a crucial mechanism for the generation of surface antigen variants. Such variation will have an impact on the interaction with the host tissues, and understanding these mechanisms is important to aid our understanding of the intimate and complex relationship between the human nasopharynx and the meningococcus. Citation: Bentley SD, Vernikos GS, Snyder LAS, Churcher C, Arrowsmith C, et al. (2007) Meningococcal genetic variation mechanisms viewed through comparative analysis of serogroup C Strain FAM18. PLoS Genet 3(2): e23.
Journal of Bacteriology, 2010
Neisseria meningitidis serogroup B strains are responsible for most meningococcal cases in the industrialized countries, and strains belonging to the clonal complex ST-41/44 are among the most prevalent serogroup B strains in carriage and disease. Here, we report the first genome and transcriptome comparison of a serogroup B carriage strain from the clonal complex ST-41/44 to the serogroup B disease strain MC58 from the clonal complex ST-32. Both genomes are highly colinear, with only three major genome rearrangements that are associated with the integration of mobile genetic elements. They further differ in about 10% of their gene content, with the highest variability in gene presence as well as gene sequence found for proteins involved in host cell interactions, including Opc, NadA, TonB-dependent receptors, RTX toxin, and two-partner secretion system proteins. Whereas housekeeping genes coding for metabolic functions were highly conserved, there were considerable differences in their expression pattern upon adhesion to human nasopharyngeal cells between both strains, including differences in energy metabolism and stress response. In line with these genomic and transcriptomic differences, both strains also showed marked differences in their in vitro infectivity and in serum resistance. Taken together, these data support the concept of a polygenic nature of meningococcal virulence comprising differences in the repertoire of adhesins as well as in the regulation of metabolic genes and suggest a prominent role for immune selection and genetic drift in shaping the meningococcal genome.