Protamine is an arginine-rich polycationic protein extracted from sperm cells of vertebrates including fishes such as salmon. The purpose of this study was to investigate the suppressive effects of protamine on the growth of oral pathogens for possible usage in dental materials. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were determined by the microdilution method. Twelve strains of oral viridans streptococci, Actinomyces naeslundii, Actinomyces odontolyticus, Enterococcus faecalis, Lactobacillus acidophilus, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis and Candida albicans were suppressed by protamine. MIC and MBC values were between 0.009～20 mg/mL and 0.019～80 mg/mL, respectively. The bactericidal activities of protamine against susceptible bacterial species were dependent on the concentration of protamine and incubation time. Based on the results of this study, protamine would be a useful compound for the development of antimicrobial agents against oral pathogens in dental materials.

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To determine whether fermented rice extract (FRe) has bifidogenic growth-stimulating effects in vitro, the effects of FRe on the growth of lactic acid bacteria and bifidobacteria were evaluated. Treatment with 0.2% FRe stimulated the growth of three strains of lactic acid bacteria (Lactobacillus acidophilus, Streptococcus thermophilus, and Bifidobacterium lactis), significantly increasing the number of cells by 11 – 53 fold after 12 – 18-h incubation compared with the control (p < 0.05). HPLC analysis indicated that the panose content of the FRe powder was 6.7%. The growth-stimulating effects of FRe on bifidobacteria and lactic acid bacteria were likely due to panose, and additional unknown and/or known substances in the FRe. Based on these results, we propose that FRe could be used as a growth stimulator for bifidogenic and lactic acid bacteria in pharmaceutical and food applications.

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Monomethylmercury (MMHg) is a potent neurotoxicant that can be bioaccumulated and biomagnified through trophic levels. Human populations whose diets contain MMHg are at risk of MMHg toxicity. The gut microbiota was identified as a potential factor causing variation in MMHg absorption and body burden. However, little is known about the role of gut microbiota on Hg transformations. We conducted a series of in vitro experiments to study the effects of dietary nutrient change on Hg metabolism and the human gut microbiota using anoxic fecal slurry incubations. We used stable Hg isotope tracers to track MMHg production and degradation and characterized the microbiota using high throughput sequencing of the 16S rRNA gene. We show that the magnitude of MMHg degradation is individual dependent and rapidly responds to changes in nutrient amendments, leading to complete degradation of the MMHg present. Although the mechanism involved remains unknown, it does not appear to involve the well-known mer operon. Our data are the first to show a nutrient dependency on the ability of the simulated human gut microbiota to demethylate MMHg. This work provides much-needed insights into individual variations in Hg absorption and potential toxicity.

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Porphyromonas gingivalis, a gramnegative anaerobe, is one of the major causative agents of periodontal disease. In this study, the effects of chlorhexidine digluconate and hydrogen peroxide on the hemin binding of P. gingivalis and coaggregation of this bacterium with oral streptococci were examined. The pretreatment of P. gingivalis W50 and 381 with chlorhexidine digluconate and hydrogen peroxide increased the hemin binding of these bacteria. The hemin binding of P. gingivalis was increased by the subminimal inhibitory concentration (MIC) of chlorhexidine digluconate. However, concentrations of hydrogen peroxide below the MIC had no effect on the hemin binding of P. gingivalis W50 and 381. Coaggregation of P. gingivalis 381 with Streptococcus oralis ATCC 9811 and Streptococcus gordonii DL1 was diminished by chlorhexidine digluconate. The coaggregation-inhibitory effect was concentrationdependent. Hydrogen peroxide also showed inhibitory effects on the coaggregation of P. gingivalis 381 with S. oralis 9811 and S. gordonii DL1 at concentrations below that used clinically. Concentrations of chlorhexidine digluconate below the MIC inhibited coaggregation. However, concentrations of hydrogen peroxide below the MIC were not effective in reducing the coaggregation of P. gingivalis with oral streptococci. These observations show that chlorhexidine digluconateand hydrogen peroxide could confer variable effects on P. gingivalis hemin binding and coaggregation of this bacterium with oral streptococci. (J. Oral Sci. 43, 1-7, 2001)

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Chronic inflammation of rheumatoid arthritis (RA) is promoted by proinflammatory cytokines and closely linked to angiogenesis. In the present study, we investigated the anti-inflammatory effects of emodin (1,3,8-trihydroxy-6-methyl-anthraquinone) isolated from the root of Rheum palmatum L. in interleukin 1 beta (IL-1β) and lipopolysaccharide (LPS)-stimulated RA synoviocytes under hypoxia. Emodin significantly inhibited IL-1β and LPS-stimulated proliferation of RA synoviocytes in a dose-dependent manner under hypoxic condition. Also, enzyme linked immunosorbent assay (ELISA) revealed that emodin significantly reduced the production of pro-inflammatory cytokines [tumor necrosis factor-alpha (TNF-α), IL-6 and IL-8], mediators [prostagladin E₂ (PGE₂), matrix metalloproteinase (MMP)-1 and MMP-13] and vascular endothelial growth factor (VEGF) as an angiogenesis biomarker in IL-1β and LPS-treated synoviocytes under hypoxia. Consistently, emodin attenuated the expression of cyclooxygenase 2 (COX-2), VEGF, hypoxia inducible factor 1 alpha (HIF-1α), MMP-1 and MMP-13 at mRNA level in IL-1β and LPS-treated synoviocytes under hypoxia. Furthermore, emodin reduced histone deacetylase (HDAC) activity as well as suppressed the expression of HDAC1, but not HDAC2 in IL-1β and LPS-treated synoviocytes under hypoxia. Overall, these findings suggest that emodin inhibits proinflammatory cytokines and VEGF productions, and HDAC1 activity in hypoxic RA synoviocytes.

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To identify exoelectrogens involved in the generation of electricity from complex organic matter in coastal sediment (CS) microbial fuel cells (MFCs), MFCs were inoculated with CS obtained from tidal flats and estuaries in the Tokyo bay and supplemented with starch, peptone, and fish extract as substrates. Power output was dependent on the CS used as inocula and ranged between 100 and 600 mW m^–2 (based on the projected area of the anode). Analyses of anode microbiomes using 16S rRNA gene amplicons revealed that the read abundance of some bacteria, including those related to Shewanella algae, positively correlated with power outputs from MFCs. Some fermentative bacteria were also detected as major populations in anode microbiomes. A bacterial strain related to S. algae was isolated from MFC using an electrode plate-culture device, and pure-culture experiments demonstrated that this strain exhibited the ability to generate electricity from organic acids, including acetate. These results suggest that acetate-oxidizing S. algae relatives generate electricity from fermentation products in CS-MFCs that decompose complex organic matter.

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From the previous findings, the ethanolic fractionated extract of Caesalpinia sappan (F-EtOH) has high activity against Streptococcus mutans, the most severe cariogenic bacteria. The present study was aimed to isolate and identify the active compound of F-EtOH and compare its inhibitory activity against the biofilm of S. mutans as well as the cytotoxicity to oral fibroblast cells with F-EtOH. Compound isolation was done by column chromatography. The active compound was identified using liquid chromatography-mass spectrometry with electrospray ionization and nuclear magnetic resonance spectroscopy. It was found that the major compound of F-EtOH is brazilin. F-EtOH and brazilin were compared for inhibitory potential on the biofilms of three strains of S. mutans. The results exhibited that both F-EtOH and brazilin had potential on inhibiting biofilm formation and eradicating the preformed biofilms and their activity was dose dependent. F-EtOH showed significantly less toxic to normal periodontal ligament fibroblast than brazilin. At low concentration of 1- and 2-MBC, F-EtOH showed higher effective than brazilin. The results of our study suggest that the antibacterial activity of F-EtOH is according to the synergistic effects of the existing compounds including brazilin in F-EtOH.

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Recycling of the nitrogenous waste uric acid (UA) of wood-feeding termites by their gut bacteria is one of the significant aspects of symbiosis for the conservation of nitrogen sources. Diverse anaerobic UA-degrading bacteria comprising 16 species were isolated from the gut of eight termite species, and were assigned to Clostridia, Enterobacteriaceae, and low G+C Gram-positive cocci. UA-degrading Clostridia had never been isolated from termite guts. UA-degrading ability was sporadically distributed among phylogenetically various culturable anaerobic bacteria from termite guts. A strain of Clostridium sp., which was commonly isolated from three termite species and represented a probable new species in cluster XIVa of clostridia, utilized UA as a nitrogen source but not as a sole carbon and energy source. This feature is in clear contrast to that of well-studied purinolytic clostridia or previously isolated UA degraders from termite guts, which also utilize UA as a sole carbon and energy source. Ammonia is the major nitrogenous product of UA degradation. Various purines stimulated the growth of this strain when added to an otherwise growth-limiting, nitrogen poor medium. The bacterial species involved the recycling of UA nitrogen in the gut microbial community of termites are more diverse in terms of both taxonomy and nutritional physiology than previously recognized.

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Sustainable livestock production requires reducing competition for food and feed resources and increasing the utilization of food by-products in livestock feed. This study describes the establishment of an anaerobic batch culture model to simulate pig microbiota and evaluate the effects of a food by-product, wakame seaweed stalks, on ex vivo microbial communities. We selected one of the nine media to support the growth of a bacterial community most similar in composition and diversity to that observed in pig donor feces. Supplementation with wakame altered the microbial profile and short-chain fatty acid composition in the ex vivo model, and a similar trajectory was observed in the in vivo pig experimental validation. Notably, the presence of wakame increased the abundance of Lactobacillus species, which may have been due to cross-feeding with Bacteroides. These results suggest the potential of wakame as a livestock feed capable of modulating the pig microbiome. Collectively, this study highlights the ability to estimate the microbiome changes that occur when pigs are fed a specific feed using an ex vivo culture model.

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