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Molecular Oral Microbiology

Jeffrey B Kaplan, Vandana Sampathkumar, Meriem Bendaoud, Alexander K Giannakakis, Edward T Lally, Nataliya V Balashova
The Gram-negative bacterium Kingella kingae is part of the normal oropharyngeal mucosal flora of children under four 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
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
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
Chengcheng Liu, Daniel P Miller, Yan Wang, Michael Merchant, Richard 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. Herein we show that the consensus BY kinase Walker A and B domains, the RK cluster and the YC domain 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
Jens Kreth, Rodrigo A Giacaman, Rahul Raghavan, Justin Merritt
The commensal oral microbial flora has evolved with the human host to support colonization of the various intraoral sites without triggering a significant immune response. In exchange, the commensal microbes provide critical protection against invading pathogens. The intrinsic ability of the oral flora to create a symbiotic microbial community with the host can be disturbed, selecting for the overgrowth of a dysbiotic community that can result in dental diseases, such as caries and periodontitis. While the mechanisms of molecular pathogenesis in oral diseases are well characterized, much less is known about the molecular mechanisms used by the commensal flora to maintain oral health...
August 1, 2016: Molecular Oral Microbiology
J A Hutcherson, H Gogeneni, D Yoder-Himes, E L Hendrickson, M Hackett, M Whiteley, R J Lamont, D A Scott
Porphyromonas gingivalis is a Gram-negative anaerobe and keystone periodontal pathogen. A mariner transposon insertion mutant library has recently been used to define 463 genes as putatively essential for the in vitro growth of P. gingivalis ATCC 33277 in planktonic culture (Library 1). We have independently generated a transposon insertion mutant library (Library 2) for the same P. gingivalis strain and herein compare genes that are putatively essential for in vitro growth in complex media, as defined by both libraries...
August 2016: Molecular Oral Microbiology
M-C Boutrin, Y Yu, C Wang, W Aruni, Y Dou, L Shi, H M Fletcher
To survive in the periodontal pocket, Porphyromonas gingivalis, the main causative agent of periodontal disease, must overcome oxidative and nitric oxide (NO) stress. Previously, we reported that, in the presence of NO comparable to stress conditions, the transcriptome of P. gingivalis was differentially expressed, and genes belonging to the PG1178-81 cluster were significantly upregulated. To further evaluate their role(s) in NO stress resistance, these genes were inactivated by allelic exchange mutagenesis...
August 2016: Molecular Oral Microbiology
C Ragunath, K DiFranco, M Shanmugam, P Gopal, V Vyas, D H Fine, C Cugini, N Ramasubbu
Among the various proteins expressed by the periodontopathogen Aggregatibacter actinomycetemcomitans, two proteins play important roles for survival in the oral cavity. The autotransporter Aae facilitates the attachment of the pathogen to oral epithelial cells, which act as a reservoir, while the biofilm-degrading glycoside hydrolase dispersin B facilitates the movement of daughter cells from the mature biofilm to a new site. The objective of this study was to use the potential of these two proteins to control biofilms...
August 2016: Molecular Oral Microbiology
A M Jesionowski, J M Mansfield, J L Brittan, H F Jenkinson, M M Vickerman
Multiple levels of interkingdom signaling have been implicated in maintaining the ecological balance between Candida albicans and commensal streptococci to assure a state of oral health. To better understand the molecular mechanisms involved in the initial streptococcal response to the presence of C. albicans that can initiate oral surface colonization and biofilm formation, hypha-forming cells were incubated with Streptococcus gordonii cells for 30 min to assess the streptococcal transcriptome response. A genome-wide microarray analysis and quantitative polymerase chain reaction validation of S...
August 2016: Molecular Oral Microbiology
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