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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
P Sanguansermsri, A H Nobbs, H F Jenkinson, R Surarit
The etiology and pathogenic mechanisms associated with canine periodontal disease are less well understood than the disease in humans. In this study we have reconstructed defined consortia biofilms in vitro of microorganisms identified as prevalent in a same-breed cohort of dogs with or without periodontal disease. Frederiksenia canicola and Neisseria canis were selected as potential early colonizers of salivary pellicle, and Fusobacterium nucleatum and Porphyromonas gulae were included as high incidence canine oral bacteria...
September 28, 2017: Molecular Oral Microbiology
Keumjin Baek, Youngnim Choi
Oral lichen planus (OLP) is a variant of LP, a common chronic mucocutaneous inflammatory disease. While cutaneous lesions of LP are self-limiting, OLP lesions are non-remissive, alternating periods of exacerbation and quiescence, and only symptomatic treatments exist for OLP. The precise etiology and pathogenesis of OLP are hardly understood, which is a major obstacle to the development of new therapeutics for this disease. OLP is considered a T cell-mediated inflammatory disease. Although various antigens have been considered, what actually triggers the inflammatory response of T cells is unknown...
September 4, 2017: Molecular Oral Microbiology
Liang Song, Guangyu Dong, Lijia Guo, Dana T Graves
Dendritic cells (DCs) are antigen-presenting cells that capture, process and present antigens to lymphocytes to initiate and regulate the adaptive immune response. DCs detect bacteria in skin and mucosa and migrate into regional lymph nodes, where they stimulate antigen-specific T and B lymphocyte activation and proliferation. DCs direct CD4 T cells to differentiate to T cell subsets such as Th1, Th2, Th17 and Treg cells. The periodontium is chronically exposed to oral bacteria that stimulate an inflammatory response to induce gingivitis or periodontitis...
August 28, 2017: Molecular Oral Microbiology
Hidenobu Senpuku, Hideo Yonezawa, Saori Yoneda, Itaru Suzuki, Ryo Nagasawa, Naoki Narisawa
The oral bacterium Streptococcus mutans is the principal agent in the development of dental caries. Biofilm formation by S. mutans requires bacterial attachment, aggregation, and glucan formation on the tooth surface under sucrose supplementation conditions. Our previous microarray analysis of clinical strains identified 74 genes in S. mutans that were related to biofilm morphology; however, the roles of almost all of these genes in biofilm formation are poorly understood. We investigated the effects of 21 genes randomly selected from our previous study regarding S...
August 28, 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
Z Chen, L Mashburn-Warren, J Merritt, M J Federle, J Kreth
The 5' untranslated region (5' UTR) of an mRNA molecule embeds important determinants that modify its stability and translation efficiency. In Streptococcus pyogenes, a strict human pathogen, a gene encoding a secreted protease (speB) has a large 5' UTR with unknown functions. Here we describe that a partial deletion of the speB 5' UTR caused a general accumulation of mRNA in the stationary phase, and that the mRNA accumulation was due to retarded mRNA degradation. The phenotype was observed in several M serotypes harboring the partial deletion of the speB 5' UTR...
October 2017: Molecular Oral Microbiology
M M Jones, S T Vanyo, M B Visser
Treponema denticola is an oral spirochete strongly associated with severe periodontal disease. A prominent virulence factor, the major outer sheath protein (Msp), disorients neutrophil chemotaxis by altering the cellular phosphoinositide balance, leading to impairment of downstream chemotactic events including actin rearrangement, Rac1 activation, and Akt activation in response to chemoattractant stimulation. The specific regions of Msp responsible for interactions with neutrophils remain unknown. In this study, we investigated the inhibitory effect of truncated Msp regions on neutrophil chemotaxis and associated signaling pathways...
October 2017: Molecular Oral Microbiology
M Rangarajan, J Aduse-Opoku, N A Paramonov, A Hashim, M A Curtis
Porphyromonas gingivalis is a Gram-negative black pigmenting anaerobe that is unable to synthesize heme [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. Porphyromonas gingivalis expresses several proteinaceous hemin-binding sites, which are important in the binding/transport of heme/hemin from the host. It also synthesizes several virulence factors, namely cysteine-proteases Arg- and Lys-gingipains and two lipopolysaccharides (LPS), O-LPS and A-LPS...
October 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...
October 2017: Molecular Oral Microbiology
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