The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Daniel C Stein - One of the best experts on this subject based on the ideXlab platform.
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sequence based predictions of lipooligosaccharide diversity in the Neisseriaceae and their implication in pathogenicity
PLOS ONE, 2011Co-Authors: Daniel C Stein, Clinton J Miller, Senthil Velan Bhoopalan, Daniel D SommerAbstract:Endotoxin [Lipopolysaccharide (LPS)/Lipooligosaccharide (LOS)] is an important virulence determinant in gram negative bacteria. While the genetic basis of endotoxin production and its role in disease in the pathogenic Neisseria has been extensively studied, little research has focused on the genetic basis of LOS biosynthesis in commensal Neisseria. We determined the genomic sequences of a variety of commensal Neisseria strains, and compared these sequences, along with other genomic sequences available from various sequencing centers from commensal and pathogenic strains, to identify genes involved in LOS biosynthesis. This allowed us to make structural predictions as to differences in LOS seen between commensal and pathogenic strains. We determined that all neisserial strains possess a conserved set of genes needed to make a common 3-Deoxy-D-manno-octulosonic acid -heptose core structure. However, significant genomic differences in glycosyl transferase genes support the published literature indicating compositional differences in the terminal oligosaccharides. This was most pronounced in commensal strains that were distally related to the gonococcus and meningococcus. These strains possessed a homolog of heptosyltransferase III, suggesting that they differ from the pathogenic strains by the presence a third heptose. Furthermore, most commensal strains possess homologs of genes needed to synthesize lipopolysaccharide (LPS). N. cinerea, a commensal species that is highly related to the gonococcus has lost the ability to make sialyltransferase. Overall genomic comparisons of various neisserial strains indicate that significant recombination/genetic acquisition/loss has occurred within the genus, and this muddles proper speciation.
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analysis of type i restriction modification systems in the Neisseriaceae genetic organization and properties of the gene products
Molecular Microbiology, 2008Co-Authors: Andrzej Piekarowicz, Aneta Klyz, Agnieszka Kwiatek, Daniel C SteinAbstract:Summary The hsd locus (host specificity of DNA) was identified in the Neisseria gonorrhoeae genome. The DNA fragment encoding this locus produced an active restriction and modification (R/M) system when cloned into Escherichia coli. This R/M system was designated NgoAV. The cloned genomic fragment (7800 bp) has the potential to encode seven open reading frames (ORFs). Several of these ORFs had significant homology with other proteins found in the databases: ORF1, the hsdM, a methylase subunit (HsdM); ORF2, a homologue of dinD ;O RF3, a homologue of hsdS; ORF4, a homologue of hsdS; and ORF5, an endonuclease subunit hsdR. The endonuclease and methylase subunits possessed strongest protein sequence homology to the EcoR124II R/M system, indicating that NgoAV belongs to the type IC R/M family. Deletion analysis showed that only ORF3 imparted the sequence specificity of the RM.NgoAV system, which recognizes an interrupted palindrome sequence (GCAN8TGC). The genetic structure of ORF3 (208 amino acids) is almost identical to the structure of the 5 0 truncated hsdS genes of Eco DXXI or Eco R124II R/M systems obtained by in vitro manipulation. Genomic sequence analysis allowed us to identify hsd loci with a very high homology to RM.NgoAV in two strains of Neisseria meningitidis. However, significant differences in the organization and structure of the hsdS genes in both these systems suggests that, if functional, they would possess recognition sites that differ from the gonococcus and from themselves.
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analysis of lipooligosaccharide biosynthesis in the Neisseriaceae
Journal of Bacteriology, 2001Co-Authors: Dan Arking, Yanhong Tong, Daniel C SteinAbstract:Neisserial lipooligosaccharide (LOS) contains three oligosaccharide chains, termed the α, β, and γ chains. We used Southern hybridization experiments on DNA isolated from various Neisseria spp. to determine if strains considered to be nonpathogenic possessed DNA sequences homologous with genes involved in the biosynthesis of these oligosaccharide chains. The presence or absence of specific genes was compared to the LOS profiles expressed by each strain, as characterized by their mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel and their reactivities with various LOS-specific monoclonal antibodies. A great deal of heterogeneity was seen with respect to the presence of genes encoding glycosyltransferases in Neisseria. All pathogenic species were found to possess DNA sequences homologous with the lgt gene cluster, a group of genes needed for the synthesis of the α chain. Some of these genes were also found to be present in strains considered to be nonpathogenic, such as Neisseria lactamica, N. subflava, and N. sicca. Some nonpathogenic Neisseria spp. were able to express high-molecular-mass LOS structures, even though they lacked the DNA sequences homologous with rfaF, a gene whose product must act before gonococcal and meningococcal LOS can be elongated. Using a PCR amplification strategy, in combination with DNA sequencing, we demonstrated that N. subflava 44 possessed lgtA, lgtB, and lgtE genes. The predicted amino acid sequence encoded by each of these genes suggested that they encoded functional proteins; however, structural analysis of LOS isolated from this strain indicated that the bulk of its LOS was not modified by these gene products. This suggests the existence of an additional regulatory mechanism that is responsible for the limited expression of these genes in this strain.
Anthony B. Schryvers - One of the best experts on this subject based on the ideXlab platform.
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The lactoferrin receptor complex in gram negative bacteria
BioMetals, 2010Co-Authors: Amanda J. Beddek, Anthony B. SchryversAbstract:Bacteria that inhabit the respiratory and genitourinary tracts of mammals encounter an iron-deficient environment on the mucosal surface where iron is complexed by the host iron-binding proteins transferrin and lactoferrin. Lactoferrin is also present in high concentrations at sites of inflammation where the cationic anti-microbial peptide lactoferricin is produced by proteolysis of lactoferrin. Several members of the Neisseriaceae and Moraxellaceae families express surface receptors, capable of specifically binding host lactoferrin and extracting the iron from lactoferrin as a source of iron for growth. The receptor is comprised of an integral outer membrane protein, lactoferrin binding protein A (LbpA), and a largely exposed surface lipoprotein, lactoferrin binding protein B (LbpB). LbpA is essential for mediating growth using lactoferrin as a sole iron source whereas LbpB only plays a facilitating role. LbpB, with the presence of a large tract of negatively charged residues, appears to protect the bacterial cell from the bactericidal effects of the lactoferricin. The lactoferrin receptors in these species appear to be essential for survival and thus may serve as potential vaccine targets.
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presence of ferric hydroxide clusters in mutants of haemophilus influenzae ferric ion binding protein a
Biochemistry, 2003Co-Authors: Stephen R Shouldice, Robert J Skene, D R Dougan, D E Mcree, Leslie W Tari, Anthony B. SchryversAbstract:The periplasmic iron binding protein plays an essential role in the iron uptake pathway of Gram-negative pathogenic bacteria from the Pasteurellaceae and Neisseriaceae families and is critical for survival of these pathogens within the host. In this study, we report the crystal structures of two mutant forms of ferric ion-binding protein A (FbpA) from Haemophilus influenzae with bound multinuclear oxometal clusters. Crystals of site-directed mutants in the metal or anion binding ligands contain protein in the open conformation, and two mutant FbpAs, H9A and N175L, contain different cluster arrangements in the iron-binding pocket. The iron clusters are anchored by binding to the two tyrosine ligands (Tyr195 and Tyr196) positioned at the vertex of the iron-binding pocket but are not coordinated by the other metal binding ligands. Our results suggest that the metal clusters may have formed in situ, suggesting that the mutant FbpAs may serve as a simple model for protein-mediated mineralization.
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Presence of Ferric Hydroxide Clusters in Mutants of Haemophilus influenzae Ferric Ion-Binding Protein A†,‡
Biochemistry, 2003Co-Authors: Stephen R Shouldice, Robert J Skene, D R Dougan, D E Mcree, Leslie W Tari, Anthony B. SchryversAbstract:The periplasmic iron binding protein plays an essential role in the iron uptake pathway of Gram-negative pathogenic bacteria from the Pasteurellaceae and Neisseriaceae families and is critical for survival of these pathogens within the host. In this study, we report the crystal structures of two mutant forms of ferric ion-binding protein A (FbpA) from Haemophilus influenzae with bound multinuclear oxometal clusters. Crystals of site-directed mutants in the metal or anion binding ligands contain protein in the open conformation, and two mutant FbpAs, H9A and N175L, contain different cluster arrangements in the iron-binding pocket. The iron clusters are anchored by binding to the two tyrosine ligands (Tyr195 and Tyr196) positioned at the vertex of the iron-binding pocket but are not coordinated by the other metal binding ligands. Our results suggest that the metal clusters may have formed in situ, suggesting that the mutant FbpAs may serve as a simple model for protein-mediated mineralization.
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Characterization of Moraxella(Branhamella) catarrhalis lbpB, lbpA, and Lactoferrin Receptor orf3 Isogenic Mutants
Infection and Immunity, 1999Co-Authors: Robert A. Bonnah, Henry Wong, Sheena M. Loosmore, Anthony B. SchryversAbstract:Pathogenic members of the family Neisseriaceae produce specific receptors to acquire iron from their host’s lactoferrin and transferrin. Recently, putative Moraxella catarrhalis lactoferrin receptor genes and a third open reading frame (lbpB, lbpA, and orf3) were cloned and sequenced. We describe the preliminary characterization of isogenic mutants deficient in LbpB, LbpA, or Orf3 protein.
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bacterial lactoferrin receptors in the Neisseriaceae
1997Co-Authors: Robert A. Bonnah, Ronghua Yu, Anthony B. SchryversAbstract:In order to survive in the iron-restricted environment of the host, bacteria have evolved efficient mechanisms for acquisition of iron from the host’s glycoproteins, transferrin (Tf) and lactoferrin (Lf). Tf receptors, which are involved in acquisition of iron specifically from host Tf, have been identified in a number of important human and veterinary pathogens from the families Neisseriaceae and Pasteurellaceae. In contrast, receptors for the host’s Lf have only been demonstrated in Neisseriaceae. Polymerase chain reaction (PCR)-based approaches for identification of the Lf receptor genes can help overcome the limitations of growth studies, and binding and affinity isolation assays for confirming the presence of the Lf receptor-mediated pathway Affinity isolation studies have demonstrated that, contrary to previous conclusions, the composition of the Lf receptor is similar to that of the Tf receptor (Tbp1 and Tbp2) and includes two proteins, Lbp1 (Tbp1 homolog) and Lbp2 (Tbp2 homolog). The parallels in composition of receptors and organization of the genetic loci for the Tf and Lf receptors enable us to propose a model for the structure and organization of the iron-acquisition pathway. Although prior studies have provided some insights into ligand-receptor interaction, further analysis will need to incorporate modifications in order to include assessment of binding by Lbp2 and will most effectively be addressed by analysis of recombinant chimeric proteins.
James T Staley - One of the best experts on this subject based on the ideXlab platform.
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phylogeny of the genus simonsiella and other members of the Neisseriaceae
International Journal of Systematic and Evolutionary Microbiology, 2002Co-Authors: Brian P Hedlund, James T StaleyAbstract:16S rDNA was sequenced from 16 strains of the oral commensal Simonsiella and was used to assess relationships between Simonsiella strains and other members of the Neisseriaceae. In all analyses, Simonsiella strains grouped according to established species designations and the mammalian hosts from which they were isolated. The commensals from cats and dogs formed a monophyletic group. The monophyly of the genus Simonsiella, however, could be neither supported nor rejected; deep nodes in the trees were unstable depending on the phylogenetic method or on the particular sequences used in the analysis. Instabilities may be attributable to frequent gene transfer between Neisseria or other members of the Neisseriaceae and Simonsiella.
T Odugbemi - One of the best experts on this subject based on the ideXlab platform.
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the occurrence of branhamella catarrhalis and other commensal Neisseriaceae in clinical sputum specimens in lagos nigeria
European Journal of Epidemiology, 1990Co-Authors: T Animashaun, T OdugbemiAbstract:Branhamella catarrhalis and other commensal Neisseria species were isolated from 200 out of 500 sputum samples from patients with lower respiratory tract (LRT) infections at the Lagos University Teaching Hospital (LUTH).
Kokgan Chan - One of the best experts on this subject based on the ideXlab platform.
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aquella oligotrophica gen nov sp nov a new member of the family Neisseriaceae isolated from laboratory tap water
MicrobiologyOpen, 2019Co-Authors: Kokgan Chan, Wahseng Seetoo, Kahooi Chua, Alvaro Peix, Karwai HongAbstract:: A bacterial strain designated as P08T was isolated from laboratory tap water during a water quality assessment in University of Malaya, Malaysia. The strain was a Gram-negative, rod-shaped, nonmotile, and aerobic bacterium. Complete genome of P08T comprised of a 2,820,660 bp chromosome with a G + C content of 36.43%. Both 16S rRNA phylogeny and phylogenetic tree inferred from the core gene matrix demonstrated that P08T formed a hitherto unknown subline within the family Neisseriaceae. Ortho average nucleotide identity (OrthoANI) values and the percentage of conserved proteins (POCP) calculated from complete genome sequence indicated low relatedness between P08T and its phylogenetic neighbors. Respiratory quinone analysis revealed Q-8 as the only detectable quinone. The predominant cellular fatty acids were identified as C14:0 , iso-C15:0 , and summed feature 3 (C16:1 ω7c/C16:1 ω6c). The polar lipids consisted of uncharacterized aminolipid, phosphatidylglycerol, and phosphatidylethanolamine. All aspects of phenotypic and phylogenetic data suggested that strain P08T represents a novel genus within family Neisseriaceae, for which the name Aquella gen. nov. is proposed. The type species of the genus is Aquella oligotrophica sp. nov., and the type strain is P08T (=LMG 29629T =DSM 100970T ).
