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Molecular Oral Microbiology

Minnie Rangarajan, Joseph Aduse-Opoku, Nikolay A Paramonov, Ahmed Hashim, Michael A Curtis
Porphyromonas gingivalis is a Gram-negative black pigmenting anaerobe unable to synthesise haem (Fe (II)-protoporphyrin IX) or hemin (Fe(III)-protoporphyrin IX-Cl) which are important growth/virulence-factors, and must therefore derive them from the host P. gingivalis expresses several proteinaceous hemin -binding-sites which are important in the binding/ transport of haem/hemin from the host. P. gingivalis also synthesises several virulence factors, namely cysteine-proteases Arg- and Lys-gingipains and two lipopolysaccharides (LPS), O-LPS and A-LPS...
January 20, 2017: Molecular Oral Microbiology
Lihong Guo, Bhumika Shokeen, Xuesong He, Wenyuan Shi, Renate Lux
Adhesin-mediated bacterial interspecies interactions are important elements in oral biofilm formation. They often occur on a species-specific level, which could determine health- or disease association of a biofilm community. Among the key players involved in these processes are the ubiquitous fusobacteria that have been recognized for their ability to interact with numerous different binding partners. Fusobacterial interactions with Streptococcus mutans, an important oral cariogenic pathogen, have previously been described but most studies focused on binding to non-mutans streptococci and specific cognate adhesin pairs remain to be identified...
December 15, 2016: Molecular Oral Microbiology
E Connolly, E Millhouse, R Doyle, S Culshaw, G Ramage, G P Moran
Porphyromonas gingivalis is a bacterium associated with chronic periodontitis that possesses a family of genes encoding hemagglutinins required for heme acquisition. In this study we generated ΔhagB and ΔhagC mutants in strain W83 and demonstrate that both hagB and hagC are required for adherence to oral epithelial cells. Unexpectedly, a double ΔhagB/ΔhagC mutant had less severe adherence defects than either of the single mutants, but was found to exhibit increased expression of the gingipain-encoding genes rgpA and kgp, suggesting that a ΔhagB/ΔhagC mutant is only viable in populations of cells that exhibit increased expression of genes involved in heme acquisition...
February 2017: Molecular Oral Microbiology
M O Freire, A Devaraj, A Young, J B Navarro, J S Downey, C Chen, L O Bakaletz, H H Zadeh, S D Goodman
Periodontal disease exemplifies a chronic and recurrent infection with a necessary biofilm component. Mucosal inflammation is a hallmark response of the host seen in chronic diseases, such as colitis, gingivitis, and periodontitis (and the related disorder peri-implantitis). We have taken advantage of our recently developed rat model of human peri-implantitis that recapitulates osteolysis, the requirement of biofilm formation, and the perpetuation of the bona fide disease state, to test a new therapeutic modality with two novel components...
February 2017: Molecular Oral Microbiology
E Hajishengallis, Y Parsaei, M I Klein, H Koo
Early childhood caries (ECC) is one of the most prevalent infectious diseases affecting children worldwide. ECC is an aggressive form of dental caries, which, left untreated, can result in rapid and extensive cavitation in teeth (rampant caries) that is painful and costly to treat. Furthermore, it affects mostly children from impoverished backgrounds, and so constitutes a major challenge in public health. The disease is a prime example of the consequences arising from complex, dynamic interactions between microorganisms, host, and diet, leading to the establishment of highly pathogenic (cariogenic) biofilms...
February 2017: Molecular Oral Microbiology
S S Garcia, Q Du, H Wu
The oral cavity is a dynamic environment characterized by hundreds of bacterial species, saliva, and an influx of nutrients and metal ions such as copper. Although there is a physiologic level of copper in the saliva, the oral cavity is often challenged with an influx of copper ions. At high concentrations copper is toxic and must therefore be strictly regulated by pathogens for them to persist and cause disease. The cariogenic pathogen Streptococcus mutans manages excess copper using the copYAZ operon that encodes a negative DNA-binding repressor (CopY), the P1-ATPase copper exporter (CopA), and the copper chaperone (CopZ)...
December 2016: Molecular Oral Microbiology
S C Crepps, E E Fields, D Galan, J P Corbett, E R Von Hasseln, G A Spatafora
SloR, a 25-kDa metalloregulatory protein in Streptococcus mutans modulates the expression of multiple genes, including the sloABC operon that encodes essential Mn(2+) transport and genes that promote cariogenesis. In this study, we report on SloC- and SloR-deficient strains of S. mutans (GMS284 and GMS584, respectively) that demonstrate compromised survivorship compared with their UA159 wild-type progenitor and their complemented strains (GMS285 and GMS585, respectively), when challenged with streptonigrin and/or in growth competition experiments...
December 2016: Molecular Oral Microbiology
T Goulas, I Garcia-Ferrer, J A Hutcherson, B A Potempa, J Potempa, D A Scott, F Xavier Gomis-Rüth
Porphyromonas gingivalis is the main causative agent of periodontitis. It deregulates the inflammatory and innate host immune responses through virulence factors, which include the immunodominant outer-membrane surface receptor antigens A (PgRagA) and B (PgRagB), co-transcribed from the rag pathogenicity island. The former is predicted to be a Ton-dependent porin-type translocator but the targets of this translocation and the molecular function of PgRagB are unknown. Phenomenologically, PgRagB has been linked with epithelial cell invasion and virulence according to murine models...
December 2016: Molecular Oral Microbiology
J B Kaplan, V Sampathkumar, M Bendaoud, A K Giannakakis, E T Lally, N V Balashova
The Gram-negative bacterium Kingella kingae is part of the normal oropharyngeal mucosal flora of children <4 years old. K. kingae can enter the submucosa and cause infections of the skeletal system in children, including septic arthritis and osteomyelitis. The organism is also associated with infective endocarditis in children and adults. Although biofilm formation has been coupled with pharyngeal colonization, osteoarticular infections, and infective endocarditis, no studies have investigated biofilm formation in K...
October 7, 2016: Molecular Oral Microbiology
Chaitra Parthiban, Dhanasekaran Varudharasu, Mayilvahanan Shanmugam, Prerna Gopal, Chandran Ragunath, Leonard Thomas, Mark Nitz, Narayanan Ramasubbu
The oral pathogen, Aggregatibacter actinomycetemcomitans, uses pga gene locus for the production of an exopolysaccharide made up of a linear homopolymer of β-1,6-N-acetyl-D-glucosamine (PGA). An enzyme encoded by the pgaB of the pga operon in A. actinomycetemcomitans is a de-N-acetylase which is used to alter the PGA. The full length enzyme (AaPgaB) and the N-terminal catalytic domain (residues 25-290, AaPgaBN) from A. actinomycetemcomitans were cloned, expressed and purified. The enzymatic activities of the AaPgaB enzymes were determined using 7-acetoxycoumarin-3-carboxylic acid as the substrate...
October 5, 2016: Molecular Oral Microbiology
W Qiu, X Zheng, Y Wei, X Zhou, K Zhang, S Wang, L Cheng, Y Li, B Ren, X Xu, Y Li, M Li
Part of the d-alanine (d-Ala) metabolic pathway in bacteria involves the conversion of l-alanine to d-Ala by alanine racemase and the formation of d-alanyl-d-alanine by d-alanine-d-alanine ligase, the product of which is involved in cell wall peptidoglycan synthesis. At present, drugs that target the metabolic pathway of d-Ala are already in clinical use - e.g. d-cycloserine (DCS) is used as an antibiotic against Mycobacterium tuberculosis. Streptococcus mutans is the main cariogenic bacterium in the oral cavity...
October 2016: Molecular Oral Microbiology
Q Ding, S Y Quah, K S Tan
Extracellular ATP (eATP) is an important intercellular signaling molecule secreted by activated immune cells or released by damaged cells. In mammalian cells, a rapid increase of ATP concentration in the extracellular space sends a danger signal, which alerts the immune system of an impending danger, resulting in recruitment and priming of phagocytes. Recent studies show that bacteria also release ATP into the extracellular milieu, suggesting a potential role for eATP in host-microbe interactions. It is currently unknown if any oral bacteria release eATP...
October 2016: Molecular Oral Microbiology
M J Gui, S G Dashper, N Slakeski, Y-Y Chen, E C Reynolds
Outer membrane vesicles (OMVs) are asymmetrical single bilayer membranous nanostructures produced by Gram-negative bacteria important for bacterial interaction with the environment. Porphyromonas gingivalis, a keystone pathogen associated with chronic periodontitis, produces OMVs that act as a virulence factor secretion system contributing to its pathogenicity. Despite their biological importance, the mechanisms of OMV biogenesis have not been fully elucidated. The ~14 times more curvature of the OMV membrane than cell outer membrane (OM) indicates that OMV biogenesis requires energy expenditure for significant curvature of the OMV membrane...
October 2016: Molecular Oral Microbiology
E L Ferreira, M T Batista, R C M Cavalcante, V R Pegos, H M Passos, D A Silva, A Balan, L C S Ferreira, R C C Ferreira
Bacterial ATP-binding cassette (ABC) transporters play a crucial role in the physiology and pathogenicity of different bacterial species. Components of ABC transporters have also been tested as target antigens for the development of vaccines against different bacterial species, such as those belonging to the Streptococcus genus. Streptococcus mutans is the etiological agent of dental caries, and previous studies have demonstrated that deletion of the gene encoding PstS, the substrate-binding component of the phosphate uptake system (Pst), reduced the adherence of the bacteria to abiotic surfaces...
October 2016: Molecular Oral Microbiology
W A Weigel, D R Demuth
The QseBC two-component system (TCS) is associated with quorum sensing and functions as a global regulator of virulence. Based on sequence similarity within the sensor domain and conservation of an acidic motif essential for signal recognition, QseBC is primarily distributed in the Enterobacteriaceae and Pasteurellaceae. In Escherichia coli, QseC responds to autoinducer-3 and/or epinephrine/norepinephrine. Binding of epinephrine/norepinephrine is inhibited by adrenergic antagonists; hence QseC functions as a bacterial adrenergic receptor...
October 2016: Molecular Oral Microbiology
T Yoo, S A Ham, J S Hwang, W J Lee, K S Paek, J W Oh, J H Kim, J T Do, C W Han, J H Kim, H G Seo
We investigated the roles of peroxisome proliferator-activated receptor δ (PPARδ) in Porphyromonas gingivalis-derived lipopolysaccharide (Pg-LPS)-induced activation of matrix metalloproteinase 2 (MMP-2). In human gingival fibroblasts (HGFs), activation of PPARδ by GW501516, a specific ligand of PPARδ, inhibited Pg-LPS-induced activation of MMP-2 and generation of reactive oxygen species (ROS), which was associated with reduced expression of NADPH oxidase 4 (Nox4). These effects were significantly smaller in the presence of small interfering RNA targeting PPARδ or the specific PPARδ inhibitor GSK0660, indicating that PPARδ is involved in these events...
October 2016: Molecular Oral Microbiology
C Withycombe, K J Purdy, S E Maddocks
Chronic wounds, including pressure ulcers, foot ulcers, and venous leg ulcers, have a detrimental impact on the health and well-being of an estimated 2% of people in the UK. Chronic wounds are normally colonized by bacteria and in some instances bacterial load increases sufficiently for infection to ensue. Once a chronic wound becomes infected it is difficult to resolve and a combination of continuous inflammation and bacterial proliferation makes these wounds difficult to manage. A state of prolonged inflammation can occur as a result of impaired homeostatic pathways, which are exacerbated by bacterial growth...
August 12, 2016: Molecular Oral Microbiology
C Liu, D P Miller, Y Wang, M Merchant, R J Lamont
The development of synergistically pathogenic communities of Porphyromonas gingivalis and Streptococcus gordonii is controlled by a tyrosine-phosphorylation-dependent signaling pathway in P. gingivalis. The Ptk1 bacterial tyrosine (BY) kinase of P. gingivalis is required for maximal community development and for the production of extracellular polysaccharide. We show that the consensus BY kinase Walker A and B domains, the RK cluster, and the YC domain of Ptk1 are necessary for autophosphorylation and for substrate phosphorylation...
August 6, 2016: Molecular Oral Microbiology
Young-Jung Jung, Yu-Jung Choi, Sun-Jin An, Hae-Ri Lee, Hye-Kyoung Jun, Bong-Kyu Choi
Tannerella forsythia is a major periodontal pathogen, and T. forsythia GroEL is a molecular chaperone homologous to human heat shock protein 60. Interleukin (IL)-17 has been implicated in the pathogenesis of periodontitis and several systemic diseases. This study investigated the potential of T. forsythia GroEL to induce inflammatory bone resorption and examined the cooperative effect of IL-17 and T. forsythia GroEL on inflammatory responses. Human gingival fibroblasts (HGFs) and periodontal ligament (PDL) fibroblasts were stimulated with T...
August 3, 2016: Molecular Oral Microbiology
Midori Doke, Haruka Fukamachi, Hirobumi Morisaki, Takafumi Arimoto, Hideo Kataoka, Hirotaka Kuwata
Periodontitis is an inflammatory disease caused by periodontal bacteria in subgingival plaque. These bacteria are able to colonize the periodontal region by evading the host immune response. Neutrophils, the host's first line of defense against infection, use various strategies to kill invading pathogens, including neutrophil extracellular traps (NETs). NETs are extracellular net-like fibers comprising DNA and antimicrobial components such as histones, LL-37, defensins, myeloperoxidase, and neutrophil elastase from neutrophils that disarm and kill bacteria extracellularly...
August 1, 2016: Molecular Oral Microbiology
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