• Journal of Microbiology and Biotechnology
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• v.23 no.5
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• pp.707-714
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• 2013

Microbially induced calcium carbonate precipitation (MICCP) is a naturally occurring biological process that has various applications in remediation and restoration of a range of building materials. In the present investigation, five ureolytic bacterial isolates capable of inducing calcium carbonate precipitation were isolated from calcareous soils on the basis of production of urease, carbonic anhydrase, extrapolymeric substances, and biofilm. Bacterial isolates were identified as Bacillus megaterium, B. cereus, B. thuringiensis, B. subtilis, and Lysinibacillus fusiformis based on 16S rRNA analysis. The calcium carbonate polymorphs produced by various bacterial isolates were analyzed by scanning electron microscopy, confocal laser scanning microscopy, X ray diffraction, and Fourier transmission infra red spectroscopy. A strain-specific precipitation of calcium carbonate forms was observed from different bacterial isolates. Based on the type of polymorph precipitated, the technology of MICCP can be applied for remediation of various building materials.

• Journal of Korean Academy of Oral Health
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• v.43 no.3
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• pp.118-123
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• 2019

Objectives: The purpose of this study was to investigate changes in the composition of artificial cariogenic biofilms using a Streptococcus mutans biofilm model over a period of time. Methods: We analyzed the dry weight, colony forming unit (CFU) number, extracellular polysaccharide (EPS) biovolume, and acid production rate of S. mutans biofilms formed on saliva-coated hydroxyapatite discs after 26 h, 50 h, 74 h, 98 h, 171 h, and 195 h. In addition, we performed a laser scanning confocal fluorescence microscopy to determine the bacterial volume, EPS biovolume, and biofilm thickness. We calculated the biofilm density using dry weight and EPS biovolume. Results: Over a period of time, there was no change in the CFU number and acid production rate of S. mutans biofilms, but there was an increase in the dry weight and EPS biovolume of S. mutans biofilms. The bacterial volume, EPS biovolume, and biofilm thickness only increased in the 50-h-old biofilm; however, no change was observed in 50-195-h-old biofilms. In addition, an increase in the biofilm density was observed over time. Conclusions: These results suggest that the acid production ability of cariogenic biofilms does not change, but the biofilm density increases over time. However, due to scientific information, further research needs to be conducted in the field of dentistry to get further insights on the progression of cariogenic biofilms over time.

• Microbiology and Biotechnology Letters
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• v.40 no.2
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• pp.83-91
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• 2012

Quorum sensing (QS) is a cell-to-cell communication system, which is used by many bacteria to regulate diverse gene expression in response to changes in population density. Bacteria recognize the differences in cell density by sensing the concentration of signal molecules such as N-acyl-homoserine lactones (AHL) and autoinducer-2 (AI-2). In particular, QS plays a key role in biofilm formation, which is a specific bacterial group behavior. Biofilms are dense aggregates of packed microbial communities that grow on surfaces, and are embedded in a self-produced matrix of extracellular polymeric substances (EPS). QS regulates biofilm dispersal as well as the production of EPS. In some bacteria, biofilm formations are regulated by c-di-GMP-mediated signaling as well as QS, thus the two signaling systems are mutually connected. Biofilms are one of the major virulence factors in pathogenic bacteria. In addition, they cause numerous problems in industrial fields, such as the biofouling of pipes, tanks and membrane bioreactors (MBR). Therefore, the interference of QS, referred to as quorum quenching (QQ) has received a great deal of attention. To inhibit biofilm formation, several strategies to disrupt bacterial QS have been reported, and many enzymes which can degrade or modify the signal molecule AHL have been studied. QQ enzymes, such as AHL-lactonase, AHL-acylase, and oxidoreductases may offer great potential for the effective control of biofilm formation and membrane biofouling in the future. This review describes the process of bacterial QS, biofilm formation, and the close relationship between them. Finally, QQ enzymes and their applications for the reduction of biofouling are also discussed.

• International Journal of Oral Biology
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• v.35 no.4
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• pp.203-207
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• 2010

A number of bacterial species coexist in oral cavities as a biofilm rather than a planktonic arrangement. By forming an oral biofilm with quorum sensing properties, microorganisms can develop a higher pathogenic potential and stronger resistance to the host immune system and antibiotics. Hence, the inhibition of biofilm formation has become a major research issue for the future prevention and treatment of oral diseases. In this study, we investigated the effects of pentose on biofilm formation and phenotypic changes using wild type oral bacteria obtained from healthy human saliva. D-ribose and D-arabinose were found to inhibit biofilm formation, but have no effects on the growth of each oral bacterium tested. Pentoses may thus be good candidate biofilm inhibitors without growth-inhibition activity and be employed for the future prevention or treatment of oral diseases.

• Environmental Engineering Research
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• v.24 no.4
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• pp.543-558
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• 2019

In comparison to alternative advanced wastewater treatment technologies, the main problem associated with membrane bioreactor (MBR) technology, which has become prominent in recent years, is biofouling. Within these systems, biofouling is typically the result of a biofilm layer resulting from bacterial gathering. One biological system that can be employed to interrupt the process of bacterial gathering is called 'Quorum Quenching (QQ)'. Existing QQ applications can be classified using three main types: 1) bacterial/whole-cell applications, 2) direct enzyme applications, and 3) natural sourced compounds. The most common and widely recognized applications for membrane fouling control during MBR operation are bacterial and direct enzyme applications. The purpose of this review was to identify and assess biofilm formation mechanism and results, the suggestion of the QQ concept and its potential to control biofilm formation, and the means by which these QQ applications can be applied within the MBR and present QQ MBR studies.

• Food Science and Biotechnology
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• v.18 no.2
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• pp.556-560
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• 2009

Xanthorrhizol, a sesquiterpene isolated from Curcuma xanthorrhiza Roxb., was used to investigate its effect on reducing the saliva and multi-species oral biofilms consisting of Streptococcus mutans, Streptococcus sanguis, and Actinomyces viscosus by anti-biofilm and confocal laser scanning microscopy (CLSM) assays. Xanthorrhizol exhibited significant antibiofilm activity in the dose- and time-dependent manners. Exposure to 2 and $5{\mu}g/mL$ xanthorrhizol for 30 min remained <50% of saliva and multi-species biofilms formed for 24 hr. In addition, exposure to $10{\mu}g/mL$ xanthorrhizol for 30 min reduced 65 and 77% of 24 hr saliva and multi-species oral biofilms, respectively. CLSM results visually demonstrated that xanthorrhizol reduced bacterial viability in the saliva and multi-species oral biofilms. These results suggest that C. xanthorrhiza Roxb. containing xanthorrhizol with strong anti-biofilm activity can be employed as a plant source for oral care functional foods.

• The Journal of Advanced Prosthodontics
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• v.11 no.2
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• pp.81-87
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• 2019

PURPOSE. The purpose of this study was to evaluate the effects of various protocols and systems for finishing and polishing monolithic zirconia on surface topography, phase transformation, and bacterial adhesion. MATERIALS AND METHODS. Three hundred monolithic zirconia specimens were fabricated and then treated with three finishing and polishing systems (Jota [JO], Meisinger [ME], and Edenta [ED]) using four surface treatment protocols: coarse finishing alone (C); coarse finishing and medium polishing (CM); coarse finishing and fine polishing (CF); and coarse finishing, medium polishing, and fine polishing (CMF). Surface roughness, crystal phase transformation, and bacterial adhesion were evaluated using atomic force microscopy, X-ray diffraction, and streptococcal biofilm formation assay, respectively. One-way and two-way analysis of variance with Tukey post hoc tests were used to analyze the results (${\alpha}=.05$). RESULTS. In this study, the surface treatment protocols and systems had significant effects on the resulting roughness. The CMF protocol produced the lowest roughness values, followed by CM and CF. Use of the JO system produced the lowest roughness values and the smallest biofilm mass, while the ME system produced the smallest partial transformation ratio. The ED group exhibited the highest roughness values, biofilm mass, and partial transformation ratio. CONCLUSION. Stepwise surface treatment of monolithic zirconia, combined with careful polishing system selection, is essential to obtaining optimal microstructural and biological surface results.

• Journal of Microbiology and Biotechnology
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• v.33 no.6
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• pp.715-723
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• 2023

Microbial biofilms are resilient, immune-evasive, often antibiotic-resistant health challenges, and increasingly the target for research into novel therapeutic strategies. We evaluated the effects of a nutraceutical enzyme and botanical blend (NEBB) on established biofilm. Five microbial strains with known implications in chronic human illnesses were tested: Candida albicans, Staphylococcus aureus, Staphylococcus simulans (coagulase-negative, penicillin-resistant), Borrelia burgdorferi, and Pseudomonas aeruginosa. The strains were allowed to form biofilm in vitro. Biofilm cultures were treated with NEBB containing enzymes targeted at lipids, proteins, and sugars, also containing the mucolytic compound N-acetyl cysteine, along with antimicrobial extracts from cranberry, berberine, rosemary, and peppermint. The post-treatment biofilm mass was evaluated by crystal-violet staining, and metabolic activity was measured using the MTT assay. Average biofilm mass and metabolic activity for NEBB-treated biofilms were compared to the average of untreated control cultures. Treatment of established biofilm with NEBB resulted in biofilm-disruption, involving significant reductions in biofilm mass and metabolic activity for Candida and both Staphylococcus species. For B. burgdorferi, we observed reduced biofilm mass, but the remaining residual biofilm showed a mild increase in metabolic activity, suggesting a shift from metabolically quiescent, treatment-resistant persister forms of B. burgdorferi to a more active form, potentially more recognizable by the host immune system. For P. aeruginosa, low doses of NEBB significantly reduced biofilm mass and metabolic activity while higher doses of NEBB increased biofilm mass and metabolic activity. The results suggest that targeted nutraceutical support may help disrupt biofilm communities, offering new facets for integrative combinational treatment strategies.

• Journal of Microbiology and Biotechnology
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• v.28 no.12
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• pp.2071-2078
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• 2018

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight, which results in severe economic damage to rice farms. Xoo produces biofilms for pathogenesis and survival both inside and outside the host. Biofilms, which are important virulence factors, play a key role in causing the symptoms of Xoo infection. In the present study, we investigated the nutritional conditions for biofilm formation by Xoo. Although Xoo biofilm formation may be initiated by interactions with the host, Xoo biofilm cannot mature without the support of favorable nutritional conditions. Nitrogen sources inhibited Xoo biofilm formation by overwhelming the positive effect that cell growth has on it. However, limited nutrients with low amino acid concentration supported biofilm formation by Xoo in the xylem sap rather than in the phloem sap of rice.

• Journal of Life Science
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• v.16 no.4
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• pp.579-583
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• 2006

The influence of disinfectant on bacterial concentration and carbon usage patterns by Biolog GN plates were investigated for biofilm on carbon steel pipe. Heterotrophic bacterial concentrations were not different among non-, monochloramine- (1.0, 1.5 mg/l) and free chlorine- (0.5, 1.0 mg/l) treated samples (P = 0.56, ANOVA). However treatment of 1.5 mg/l free chlorine and 2.0 mg/l monochloraime showed significantly lower densities than control (P < 0.01, ANOVA). By the stepwise increasement of disinfectant concentration, the carbon usage activities of biofilm microflora were decreased after increase without the decrease of bacterial concentration, following reduction of cell density. Carbon usage patterns were qualitatively and quantitatively different with similar bacterial concentrations. Principal component analysis suggested that type and concentration of disinfectant were main factors on the usage of carbons. Our result suggest that the differences of bacterial communities were different among the samples and the need of monochloramine for the reduction of biofilm in drinking water.