Research Interests: Biochemistry, Microbiology, Mathematics, Biology, Infectious Diseases, and 15 moreGlycobiology, Bacterial Diseases, Medicine, Biological Sciences, Enzymes, Markov chains, Escherichia coli, Glycoproteins, Glycosylation, Acinetobacter, Glycosyltransferases, Bacterial, Amino Acid Sequence, Bacterial Pathogens, and Markov model
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Pili of Neisseria meningitidis are a key virulence factor, being the major adhesin of this capsulate organism and contributing to specificity for the human host. Pili are post-translationally modified by addition of either an O-linked... more
Pili of Neisseria meningitidis are a key virulence factor, being the major adhesin of this capsulate organism and contributing to specificity for the human host. Pili are post-translationally modified by addition of either an O-linked trisaccharide, Gal (beta1-4) Gal (alpha1-3) 2,4-diacetamido-2,4,6-trideoxyhexose or an O-linked disaccharide Gal (alpha1,3) GlcNAc. The role of these structures in meningococcal pathogenesis has not been resolved. In previous studies we identified two separate genetic loci, pglA and pglBCD, involved in pilin glycosylation. Putative functions have been allocated to these genes; however, there are not enough genes to account for the complete biosynthesis of the described structures, suggesting additional genes remain to be identified. In addition, it is not known why some strains express the trisaccharide structure and some the disaccharide structure. In order to find additional genes involved in the biosynthesis of these structures, we used the recently published group A strain Z2491 and group B strain MC58 Neisseria meningitidis genomes and the unfinished Neisseria meningitidis group C strain FAM18 and Neisseria gonorrhoeae strain FA1090 genomes to identify novel genes involved in pilin glycosylation, based on homology to known oligosaccharide biosynthetic genes. We identified a new gene involved in pilin glycosylation designated pglE and examined four additional genes pglB/B2, pglF, pglG and pglH. A strain survey revealed that pglE and pglF were present in each strain examined. The pglG, pglH and pglB2 polymorphisms were not found in strain C311 musical sharp 3 but were present in a large number of clinical isolates. Insertional mutations were constructed in pglE and pglF in N. meningitidis strain C311 musical sharp 3, a strain with well-defined lipopolysaccharide (LPS) and pilin-linked glycan structures. Increased gel migration of the pilin subunit molecules of pglE and pglF mutants was observed by Western analysis, indicating truncation of the trisaccharide structure. Antisera specific for the C311 musical sharp 3 trisaccharide failed to react with pilin from these pglE and pglF mutants. GC-MS analysis of the sugar composition of the pglE mutant showed a reduction in galactose compared with C311 musical sharp 3 wild type. Analysis of amino acid sequence homologies has suggested specific roles for pglE and pglF in the biosynthesis of the trisaccharide structure. Further, we present evidence that pglE, which contains heptanucleotide repeats, is responsible for the phase variation between trisaccharide and disaccharide structures in strain C311 musical sharp 3 and other strains. We also present evidence that pglG, pglH and pglB2 are potentially phase variable.
Research Interests: Genetics, Bacteriology, Biology, Infectious Diseases, Medicine, and 15 moreBiological Sciences, Identification, Endothelial Cells, Microbial Genetics, Gene, Glycosylation, Genetic Polymorphism, Amino Acid Sequence, Base Sequence, Locus, C, Haemophilus influenzae, Antigenic Variation, Carbohydrate Sequence, and Medical and Health Sciences
The Neisseria gonorrhoeae pglA gene has two alleles, one of which is phase variable. A previous study reported that all disseminated gonococcal infection (DGI) isolates contained the phase-variable allele and proposed a causal link. In... more
The Neisseria gonorrhoeae pglA gene has two alleles, one of which is phase variable. A previous study reported that all disseminated gonococcal infection (DGI) isolates contained the phase-variable allele and proposed a causal link. In the present study of 81 strains no absolute correlation between DGI and the phase-variable pglA allele was observed.
Research Interests: Microbiology, Immunology, Biology, Infectious Diseases, Medicine, and 15 moreBiological Sciences, DNA, Identification, Humans, Neisseria, Glycosylation, Antimicrobial Cationic Peptides, Bacterial infections, Allele, Neisseria gonorrhoeae, alleles, gonococcal infection, Neisseria meningitidis, Medical and Health Sciences, and gonorrhea
Research Interests: Microbiology, Immunology, Medical Microbiology, Biology, Infectious Diseases, and 15 moreMedicine, Biological Sciences, Humans, Endothelial Cells, Mutation, Phenotype, Glycosylation, Molecular cloning, Lipopolysaccharides, Molecular Characterization, Molecular weight, C, Molecular Sequence Data, Neisseria meningitidis, and Cardiovascular medicine and haematology
Research Interests: Microbiology, Polymorphism, Biology, Infectious Diseases, Medicine, and 15 moreMicrobial Genetics, Neisseria, Glycosylation, Nitrite Reductase, Nitrite reductases, Protein Conformation, Amino Acid Sequence, C, ANIA, Biochemistry and cell biology, Neisseria gonorrhoeae, Haemophilus influenzae, Molecular Sequence Data, Neisseria meningitidis, and Medical biochemistry and metabolomics
The Helicobacter pylori phase variable gene modH, typified by gene HP1522 in strain 26695, encodes a N6-adenosine type III DNA methyltransferase. Our previous studies identified multiple strain-specific modH variants (modH1 - modH19) and... more
The Helicobacter pylori phase variable gene modH, typified by gene HP1522 in strain 26695, encodes a N6-adenosine type III DNA methyltransferase. Our previous studies identified multiple strain-specific modH variants (modH1 - modH19) and showed that phase variation of modH5 in H. pylori P12 influenced expression of motility-associated genes and outer membrane protein gene hopG. However, the ModH5 DNA recognition motif and the mechanism by which ModH5 controls gene expression were unknown. Here, using comparative single molecule real-time sequencing, we identify the DNA site methylated by ModH5 as 5'-Gm6ACC-3'. This motif is vastly underrepresented in H. pylori genomes, but overrepresented in a number of virulence genes, including motility-associated genes, and outer membrane protein genes. Motility and the number of flagella of H. pylori P12 wild-type were significantly higher than that of isogenic modH5 OFF or ΔmodH5 mutants, indicating that phase variable switching of modH...
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Non-typeable Haemophilus influenzae contains an N6-adenine DNA-methyltransferase (ModA) that is subject to phase-variable expression (random ON/OFF switching). Five modA alleles, modA2, modA4, modA5, modA9 and modA10, account for over... more
Non-typeable Haemophilus influenzae contains an N6-adenine DNA-methyltransferase (ModA) that is subject to phase-variable expression (random ON/OFF switching). Five modA alleles, modA2, modA4, modA5, modA9 and modA10, account for over two-thirds of clinical otitis media isolates surveyed. Here, we use single molecule, real-time (SMRT) methylome analysis to identify the DNA-recognition motifs for all five of these modA alleles. Phase variation of these alleles regulates multiple proteins including vaccine candidates, and key virulence phenotypes such as antibiotic resistance (modA2, modA5, modA10), biofilm formation (modA2) and immunoevasion (modA4). Analyses of a modA2 strain in the chinchilla model of otitis media show a clear selection for ON switching of modA2 in the middle ear. Our results indicate that a biphasic epigenetic switch can control bacterial virulence, immunoevasion and niche adaptation in an animal model system.
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Phase variation (random ON/OFF switching) of gene expression is a common feature of host-adapted pathogenic bacteria. Phase variably expressed N(6)-adenine DNA methyltransferases (Mod) alter global methylation patterns resulting in... more
Phase variation (random ON/OFF switching) of gene expression is a common feature of host-adapted pathogenic bacteria. Phase variably expressed N(6)-adenine DNA methyltransferases (Mod) alter global methylation patterns resulting in changes in gene expression. These systems constitute phase variable regulons called phasevarions. Neisseria meningitidis phasevarions regulate genes including virulence factors and vaccine candidates, and alter phenotypes including antibiotic resistance. The target site recognized by these Type III N(6)-adenine DNA methyltransferases is not known. Single molecule, real-time (SMRT) methylome analysis was used to identify the recognition site for three key N. meningitidis methyltransferases: ModA11 (exemplified by M.NmeMC58I) (5'-CGY M6A: G-3'), ModA12 (exemplified by M.Nme77I, M.Nme18I and M.Nme579II)…
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Research Interests: Genetics, Biology, Research, Horizontal Gene Transfer, Medicine, and 15 moreAntibiotic Resistance, Biological Sciences, Environmental Sciences, Microbial genetic and drug resistance, GC content, Comparative Analysis, Molecular Phylogenetics and Evolution, Genome, Gene, Bacterial Diversity, Base Sequence, Antibiotic Susceptibility, Haemophilus influenzae, Molecular Sequence Data, and host adaptation
Research Interests: Microbiology, Immunology, Medical Microbiology, Biology, Cell Biology, and 15 moreInfectious Diseases, Bacterial Diseases, Medicine, Platelet, Humans, Epithelial cells, Airway, Adherence, Receptor, Virulence factor, Modifications, Bacterial Adhesion, Cell Membrane, Neisseria meningitidis, and phosphorylcholine
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Research Interests: Genetics, Microbiology, Molecular Biology, Biology, Helicobacter pylori, and 15 moreMedicine, Biological Sciences, Escherichia coli, Campylobacter, Pseudomonas, Neisseria, Aeromonas, Glycosylation, Applied Microbiology and Biotechnology, Gram-negative bacteria, Campylobacter jejuni, Flagellin, Glycosyltransferase, Neisseria meningitidis, and Medical and Health Sciences
Research Interests: Microbiology, Medical Microbiology, Biology, Research, Medicine, and 14 moreEmerging Infectious Diseases, Virulence, Phylogeny, Humans, Gene Order, Genome, Clinical Sciences, Public health systems and services research, Host Pathogen Interactions, Virulence Factors, Haemophilus Infections Market, Haemophilus influenzae, Molecular Sequence Data, and Sequence homology
Background Haemophilus influenzae is an important human commensal pathogen associated with significant levels of disease. High-throughput DNA sequencing was used to investigate differences in genome content within this species. Results... more
Background Haemophilus influenzae is an important human commensal pathogen associated with significant levels of disease. High-throughput DNA sequencing was used to investigate differences in genome content within this species. Results Genomic DNA sequence was obtained from 85 strains of H. influenzae and from other related species, selected based on geographical site of isolation, disease association and documented genotypic and phenotypic differences. When compared by Mauve alignment these indicated groupings of H. influenzae that were consistent with previously published analyses; c apsule expressing strains fell into two distinct groups and those of serotype b (Hib) were found in two closely positioned lineages. For 18 Hib strains representing both lineages we found many discrete regions (up to 40% of the total genome) displaying sequence variation when compared to a common reference strain. Evidence that this naturally occurring pattern of inter-strain variation in H. influenza...
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Research Interests: Genetics, Microbiology, Biophysics, Biology, Protein, and 15 moreMedicine, Gene expression, Biological Sciences, Escherichia coli, Genome Analysis, Leader, Genome, Biochemical, Gene, Codon Usage, Codon, C, Protein Biosynthesis, Biochemistry and cell biology, and Medical biochemistry and metabolomics
Background Microsatellites are short DNA repeats (eg. ATATAT). They are found in the vast majority of sequenced genomes, both eukaryotic and prokaryotic. An important property is that they randomly change in length during genome... more
Background Microsatellites are short DNA repeats (eg. ATATAT). They are found in the vast majority of sequenced genomes, both eukaryotic and prokaryotic. An important property is that they randomly change in length during genome replication. If a microsatellite is present in a gene, the ...