Project description:Microarray comparative genome hybridization (mCGH) data was 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.
Project description:In bacteria and archaea, CRISPR loci confer adaptive, sequence-based immunity against viruses and plasmids. CRISPR interference is specified by CRISPR RNAs (crRNAs) that are transcribed and processed from CRISPR spacers and repeats. Pre-crRNA processing is essential for CRISPR interference in all systems studied thus far. Here we examine crRNA biogenesis and CRISPR interference in naturally competent Neisseria spp., including the human pathogen N. meningitidis. Our studies reveal a unique crRNA maturation pathway in which crRNA transcription is driven by promoters that are embedded within each repeat, yielding crRNA 5’ ends are not formed by processing. Although crRNA 3’ end formation occurs through RNase III cleavage of a pre-crRNA/tracrRNA duplex, as in other Type II CRISPR systems, this processing event is dispensable for interference. The meningococcal pathway is the most streamlined CRISPR/cas system characterized to date. Endogenous CRISPR spacers frequently target genomic sequences of other Neisseria strains and so limit natural transformation, which is the primary source of genetic variation that contributes to immune evasion, antibiotic resistance, and virulence in N. meningitidis.
Project description:In bacteria and archaea, CRISPR loci confer adaptive, sequence-based immunity against viruses and plasmids. CRISPR interference is specified by CRISPR RNAs (crRNAs) that are transcribed and processed from CRISPR spacers and repeats. Pre-crRNA processing is essential for CRISPR interference in all systems studied thus far. Here we examine crRNA biogenesis and CRISPR interference in naturally competent Neisseria spp., including the human pathogen N. meningitidis. Our studies reveal a unique crRNA maturation pathway in which crRNA transcription is driven by promoters that are embedded within each repeat, yielding crRNA 5’ ends are not formed by processing. Although crRNA 3’ end formation occurs through RNase III cleavage of a pre-crRNA/tracrRNA duplex, as in other Type II CRISPR systems, this processing event is dispensable for interference. The meningococcal pathway is the most streamlined CRISPR/cas system characterized to date. Endogenous CRISPR spacers frequently target genomic sequences of other Neisseria strains and so limit natural transformation, which is the primary source of genetic variation that contributes to immune evasion, antibiotic resistance, and virulence in N. meningitidis. dRNA-seq approach for RNA samples from cultures of N. lactamica 020-06, harvested at mid-log. Two cDNA libraries from total RNA were prepared to distinguish between transcripts with either primary orprocessed 5’ ends: one library is generated from untreated RNA, whereas the other is treated with terminator exonuclease (TEX),
Project description:BACKGROUND:The genus Neisseria contains two important yet very different pathogens, N. meningitidis and N. gonorrhoeae, in addition to non-pathogenic species, of which N. lactamica is the best characterized. Genomic comparisons of these three bacteria will provide insights into the mechanisms and evolution of pathogenesis in this group of organisms, which are applicable to understanding these processes more generally. RESULTS:Non-pathogenic N. lactamica exhibits very similar population structure and levels of diversity to the meningococcus, whilst gonococci are essentially recent descendents of a single clone. All three species share a common core gene set estimated to comprise around 1190 CDSs, corresponding to about 60% of the genome. However, some of the nucleotide sequence diversity within this core genome is particular to each group, indicating that cross-species recombination is rare in this shared core gene set. Other than the meningococcal cps region, which encodes the polysaccharide capsule, relatively few members of the large accessory gene pool are exclusive to one species group, and cross-species recombination within this accessory genome is frequent. CONCLUSION:The three Neisseria species groups represent coherent biological and genetic groupings which appear to be maintained by low rates of inter-species horizontal genetic exchange within the core genome. There is extensive evidence for exchange among positively selected genes and the accessory genome and some evidence of hitch-hiking of housekeeping genes with other loci. It is not possible to define a 'pathogenome' for this group of organisms and the disease causing phenotypes are therefore likely to be complex, polygenic, and different among the various disease-associated phenotypes observed.
Project description:The zur regulon in Neisseria meningitidis was elucidated in the strain MC58 using a zur knockout strain and conditions which activate Zur ( zinc supplementation in the medium)
Project description:Neisseria meningitidis is an obligate commensal colonising the human nasopharynx and occasionally invades the bloodstream causing life-threatening meningitis and septicaemia. The gene NMB0419 on the genome of N. meningitidis MC58 encodes a putative Sel1-like repeat (SLR) containing protein, which has been implicated in mediating meningococcal invasion of epithelial cells. We prepared RNA samples from N. meningitidis MC58 (WT) and its isogenic mutant of NMB0419 grown to log phase in in-vitro culture. The RNA samples were subjected to RNA sequencing. The resulting transcriptomes were compared to determine the genes that differentially expressed in NMB0419 mutant.
Project description:Wild type Neisseria gonorrhoea strain FA1090 and N. meningitidis strain MC58 were grown on normal GC plate at either 35 degree celsius (for control samples) or 40 degree celsius (for test samples)
Project description:In Neisseria meningitidis iron responsive gene regulation is mediated primarily by the Ferric Uptake Regulator (Fur) protein. When complexed with iron, Fur represses gene expression by preventing transcription initiation. Fur can also indirectly activate gene expression via the repression of regulatory small RNAs (sRNA). One such Fur-and iron-regulated sRNA, NrrF, was previously identified in N. meningitidis and shown to repress expression of the sdhA and sdhC genes encoding subunits of the succinate dehydrogenase complex. In the majority of Gram-negative bacteria sRNA-mediated regulation requires a cofactor RNA-binding protein (Hfq) for proper gene regulation and stabilization. In this study we examined the role of Hfq in NrrF-mediated regulation of the succinate dehydrogenase genes in N. meningitidis and the effect of an hfq- mutation on iron-responsive gene regulation more broadly. We first demonstrated that the stability of Nrrf as well as the regulation of sdhC and sdhA in vivo was unaltered in the hfq- mutant. Secondly, we established that iron responsive gene regulation of the Fur-regulated sodB gene was dependent on Hfq. Finally, we demonstrate that in N. meningitidis Hfq functions to control expression of both ORFs and intergenic regions via iron independent mechanisms. Collectively these studies demonstrate that in N. meningitidis iron and NrrF mediated regulation of sdhC and sdhA can occur independently of Hfq, although Hfq functions more globally to control regulation of other N. meningitidis genes primarily by iron-independent mechanisms.