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Molecular Oral Microbiology

Thomas Thurnheer, Georgios N Belibasakis
Bacteria residing in oral biofilms live in a state of dynamic equilibrium with one another. The intricate synergistic or antagonistic interactions between them are crucial for determining this balance. Using the 6-species Zürich "supragingival" biofilm model, this study aimed to investigate interactions regarding growth and localization of the constituent species. As control, an inoculum containing all six strains was used, whereas in each of the further five inocula one of the bacterial species was absent, and in the last both streptococci were absent...
January 11, 2018: Molecular Oral Microbiology
Blair Schneider, Whitney Weigel, Maryta Sztukowska, Donald R Demuth
Type II toxin/antitoxin (TA) systems contribute to the formation of persister cells and biofilm formation for many organisms. A. actinomycetemcomitans thrives in the complex oral microbial community subjected to continual environmental flux. Little is known regarding the presence and function of type II TA systems in this organism or their contribution to adaptation and persistence in the biofilm. We identified 11 TA systems that are conserved across all seven serotypes of A. actinomycetemcomitans and represent the RelBE, MazEF and HipAB families of type II TA systems...
January 10, 2018: Molecular Oral Microbiology
Takanori Sobue, Martinna Bertolini, Angela Thompson, Douglas E Peterson, Patricia I Diaz, Anna Dongari-Bagtzoglou
Oral mucositis is a common side effect of cancer chemotherapy, with significant adverse impact on the delivery of anti-neoplastic treatment. There is lack of consensus regarding the role of oral commensal microorganisms in the initiation or progression of mucositis since relevant experimental models are non-existent. The goal of this study was to develop an in vitro mucosal injury model that mimics chemotherapy-induced mucositis, where the effect of oral commensals can be studied. A novel organotypic model of chemotherapy-induced mucositis was developed based on a human oral epithelial cell line and a fibroblast-embedded collagen matrix...
January 4, 2018: Molecular Oral Microbiology
Richard Bauer, Stefanie Mauerer, Aline Grempels, Barbara Spellerberg
Streptococcus anginosus is considered a human commensal but improvements in species identification in recent years highlighted its role as an emerging pathogen. However, our knowledge about the pathogenicity mechanisms in this species is rare. One reason for this is the lack of published genetic manipulation techniques in the Streptococcus anginosus group. To establish a novel mutation technique we investigated the competence system of S. anginosus and created a Cre-recombinase based mutation method that allows the generation of markerless gene deletions in S...
December 31, 2017: Molecular Oral Microbiology
Elkin Jahir Florez Salamanca, Marlise Inêz Klein
Caries etiology is biofilm-diet dependent. Biofilms are highly dynamic and structured microbial communities enmeshed in a three-dimensional extracellular matrix. The study evaluated the expression dynamics of Streptococcus mutans genes associated with exopolysaccharides (EPS) (gtfBCD, gbpB, dexA), lipoteichoic acids (LTA) (dltABCD, SMU_775c) and extracellular DNA (eDNA) (lytST, lrgAB, ccpA) during matrix development within a mixed-species biofilm of S. mutans, Actinomyces naeslundii and Streptococcus gordonii...
December 28, 2017: Molecular Oral Microbiology
Angela Ruscitto, Ashu Sharma
Tannerella forsythia is a Gram-negative oral pathogen strongly associated with periodontitis. This bacterium has an absolute requirement for exogenous N-acetylmuramic acid (MurNAc), an amino sugar which forms the repeating disaccharide unit with amino sugar N-acetylglucosamine (GlcNAc) of the peptidoglycan backbone. In silico genome analysis indicates that T. forsythia lacks the key biosynthetic enzymes needed for the de novo synthesis of MurNAc, and thus relies on alternative ways to meet its requirement for peptidoglycan biosynthesis...
December 15, 2017: Molecular Oral Microbiology
Braulio Valdebenito, P Omar Tullume-Vergara, Wendy González, Jens Kreth, Rodrigo A Giacaman
During dental caries, the dental biofilm modifies the composition of the hundreds of involved bacterial species. Changing environmental conditions predisposes competition. A pertinent model to exemplify the complex interplay of the microorganisms in the human dental biofilm is the competition between Streptococcus sanguinis (S. sanguinis) and Streptococcus mutans (S. mutans). It has been reported that children and adults harbor greater numbers of S. sanguinis in the oral cavity, associated with carious-free teeth...
December 13, 2017: Molecular Oral Microbiology
Susanne Bloch, Stephanie Zwicker, Nagihan Bostanci, Åsa Sjöling, Elisabeth A Boström, Georgios N Belibasakis, Christina Schäffer
The oral pathogen Tannerella forsythia possesses a unique surface (S-) layer with a complex O-glycan containing a bacterial sialic acid mimic in the form of either pseudaminic acid or legionaminic acid at its terminal position. We hypothesize that different T. forsythia strains employ these stereoisomeric sugar acids for interacting with the immune system and resident host tissues in the periodontium. Here, we show how T. forsythia strains ATCC 43037 and UB4, displaying pseudaminic acid and legionaminic acid, respectively, and selected cell surface mutants of these strains, modulate the immune response in monocytes and human oral keratinocytes (HOK) using a multiplex immunoassay...
December 12, 2017: Molecular Oral Microbiology
Maria Rapala-Kozik, Oliwia Bochenska, Dorota Zajac, Justyna Karkowska-Kuleta, Mariusz Gogol, Marcin Zawrotniak, Andrzej Kozik
The increased incidence of severe disseminated infections caused by opportunistic yeast-like fungi Candida spp. highlights the urgent need for research into the major virulence factors of these pathogens - extracellular aspartic proteinases of the candidapepsin and yapsin families. Classically, these enzymes were considered to be generally destructive factors that damage host tissues and provide nutrients for pathogen propagation. However, in recent decades, novel and more specific functions have been suggested for extracellular candidal proteinases...
November 15, 2017: Molecular Oral Microbiology
Jill C Robinson, Nadia Rostami, John Casement, Waldemar Vollmer, Alexander H Rickard, Nicholas S Jakubovics
Biofilm formation and cell-cell sensing by the pioneer dental plaque coloniser Streptococcus gordonii is dependent upon arginine. This study aimed to identify genetic factors linking arginine-dependent responses and biofilm formation in S. gordonii. Isogenic mutants disrupted in genes required for biosynthesis or catabolism of arginine, or for arginine-dependent gene regulation, were screened for their ability to form biofilms in a static culture model. Biofilm formation by a knockout mutant of arcR, encoding an arginine-dependent regulator of transcription, was reduced to <50% that of the wild-type whereas other strains were unaffected...
November 15, 2017: Molecular Oral Microbiology
Clifford J Beall, Elaine M Mokrzan, Ann L Griffen, Eugene J Leys
A novel bacterium was isolated from the subgingival plaque of a patient with periodontal disease. Bacterial strain BA112(T) is a facultative gram-positive coccus. It metabolizes alanine, arginine, glycine, histidine, leucine, proline, serine, and tyrosine, but does not appear to utilize carbohydrates. Urease, esculin, indole, catalase, and nitrate reduction tests were all negative. Major cellular fatty acids were C18:0 , C12:0 , C16:0 , C18:1 w9c, and C20:0. The genome was sequenced and is 2.4 Mbp in length and has 64% GC content...
November 4, 2017: Molecular Oral Microbiology
Yuetan Dou, Hiel Rutanhira, Xin Chen, Arunima Mishra, Charles Wang, Hansel M Fletcher
In Porphyromonas gingivalis, PG1660 composed of 174 amino acids, is annotated as an extracytoplasmic function (ECF) sigma factor (RpoE homologue-σ24). Because PG1660 can modulate several virulence factors and responds to environmental signals in P. gingivalis, its genetic properties were further evaluated. PG1660 is co-transcribed with its downstream gene PG1659, and the transcription start site was identified as an adenine residue 54-nt upstream of the ATG translation start codon. In addition to binding its own promoter, using the purified rPG1660 and RNAP core enzyme from E...
October 23, 2017: Molecular Oral Microbiology
T Hoppe, V Göser, D Kraus, R Probstmeier, M Frentzen, M Wenghoefer, S Jepsen, J Winter
The present in-vitro-study examines molecular processes relevant during bone homeostasis after Aggregatibacter actinomycetemcomitans (A.a.) and Porphyromonas gingivalis (P.g.) infection with a focus on the differentiation level of osteoblasts. Regenerative processes are often hindered by the recurrence of bacterial infections, which can ultimately provoke a severe destruction of bone tissue. To get more detailed insights into such a complex scenario, we have used undifferentiated MG63 osteoblast-like cells as an experimental paradigm to examine the impact of two oral pathogens, A...
October 9, 2017: Molecular Oral Microbiology
Yongchao Zhu, Ting An, Ying Liu, Zilu Zhang, Qiubo Yang
The principal etiologic agent in periodontal disease, Porphyromonas gingivalis, generates cysteine proteases that bind heme with domains such as hemagglutinin-2 (HA2). High-affinity HA2-hemin binding supplies the porphyrin and ferric iron needed for growth and virulence. The DHYAVMISK peptide, recently identified at the hemin-binding site of HA2 inhibits hemin binding. We now evaluate the protective effect of vaccination with DGFPGDHYAVMISK (termed DK) against P. gingivalis using a rat infection model. Rats immunized with DK generated anti-peptide serum IgGs and salivary sIgAs (as measured by ELISA)...
October 6, 2017: Molecular Oral Microbiology
Diego F Gualtero, Gloria I Lafaurie, Marta Raquel Fontanilla
Epidemiological studies have established a clinical association between periodontal disease and atherosclerosis. Bacteremia and endotoxemia episodes in patients with periodontitis appear to link these two diseases by inducing a body-wide production of cardiovascular markers. The presence of oral bacteria in atherosclerotic lesions in patients with periodontitis suggests that bacteria, or their antigenic components, induce alterations in the endothelium associated with atherosclerosis. Therefore, a causal mechanism explaining the association between both diseases can be constructed using in vitro models...
October 6, 2017: Molecular Oral Microbiology
G Hajishengallis, R J Lamont
No abstract text is available yet for this article.
October 5, 2017: Molecular Oral Microbiology
Mikio Shoji, Keiko Sato, Hideharu Yukitake, Arihide Kamaguchi, Yuko Sasaki, Mariko Naito, Koji Nakayama
Porphyromonas gingivalis can synthesize both A-LPS and O-LPS, which contain anionic O-polysaccharides and conventional O-polysaccharides, respectively. A-LPS can anchor virulence proteins to the cell surface, and elucidating the mechanism of A-LPS synthesis is therefore important for understanding the pathogenicity of this bacterium. To identify the genes involved in LPS synthesis, we focused on uncharacterized genes encoding the glycosyltransferases, PGN_0361, PGN_ 1239, PGN_1240, and PGN_1668, which were tentatively named gtfC, gtfD, gtfE, and gtfF, respectively, and characterized their mutants...
October 3, 2017: Molecular Oral Microbiology
Senthil K Velusamy, Vandana Sampathkumar, Dipti Godboley, Daniel H Fine
Experiments were designed to explore a prominent autoinducer-2 (AI-2) producing gene (luxS) related to colonization and survival of Aggregatibacter actinomycetemcomitans, a low abundance member of the indigenous flora, that forms a key component of the dysbiotic flora in localized aggressive periodontitis. The luxS gene was disrupted in a primate strain of A. actinomycetemcomitans before implantation into the oral cavity of Rhesus monkeys (Rh). The colonization efficiency of the luxS mutant (RhAa-VS4) was compared with the parental wild-type strain (RhAa3) (positive control) and a ltxA mutant (RhAa-VS2) (negative control)...
October 2017: Molecular Oral Microbiology
Susanne Bloch, Thomas Thurnheer, Yukitaka Murakami, Georgios N Belibasakis, Christina Schäffer
As a member of subgingival multispecies biofilms, Tannerella forsythia is commonly associated with periodontitis. The bacterium has a characteristic cell surface (S-) layer modified with a unique O-glycan. Both the S-layer and the O-glycan were analyzed in this study for their role in biofilm formation by employing an in vitro multispecies biofilm model mimicking the situation in the oral cavity. Different T. forsythia strains and mutants with characterized defects in cell surface composition were incorporated into the model, together with nine species of select oral bacteria...
October 2017: Molecular Oral Microbiology
Livia A Alves, Erika N Harth-Chu, Thais H Palma, Rafael N Stipp, Flávia S Mariano, José F Höfling, Jacqueline Abranches, Renata O Mattos-Graner
Streptococcus mutans, a dental caries pathogen, can promote systemic infections upon reaching the bloodstream. The two-component system (TCS) VicRKSm of S. mutans regulates the synthesis of and interaction with sucrose-derived exopolysaccharides (EPS), processes associated with oral and systemic virulence. In this study, we investigated the mechanisms by which VicRKSm affects S. mutans susceptibility to blood-mediated immunity. Compared with parent strain UA159, the vicKSm isogenic mutant (UAvic) showed reduced susceptibility to deposition of C3b of complement, low binding to serum immunoglobulin G (IgG), and low frequency of C3b/IgG-mediated opsonophagocytosis by polymorphonuclear cells in a sucrose-independent way (P<...
October 2017: Molecular Oral Microbiology
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