• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3726-3729
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• 2011

Biofilm formation is inevitable in a bioelectrochemical system in which microorganisms act as a sole biocatalyst. Cathodic biofilm (CBF) works as a double-edged sword in the performance of the air-cathode microbial fuel cells (MFCs). Proton and oxygen crossover through the CBF are limited by the robust structure of extracellular polymeric substances, composition of available constituents and environmental condition from which the biofilm is formed. The MFC performance in terms of power, current and coulombic efficiency is influenced by the nature and origin of CBF. Development of CBF from different ecological environment while keeping the same anode inoculums, contributes additional charge transfer resistance to the total internal resistance, with increase in coulombic efficiency at the expense of power reduction. This study demonstrates that MFC operation conditions need to be optimized on the choice of initial inoculum medium that leads to the biofilm formation on the air cathode.

• Restorative Dentistry and Endodontics
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• v.44 no.1
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• pp.7.1-7.10
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• 2019

Apical periodontitis is a biofilm-mediated infection. The biofilm protects bacteria from host defenses and increase their resistance to intracanal disinfecting protocols. Understanding the virulence of these endodontic microbiota within biofilm is essential for the development of novel therapeutic procedures for intracanal disinfection. Both the disruption of biofilms and the killing of their bacteria are necessary to effectively treat apical periodontitis. Accordingly, a review of endodontic biofilm types, antimicrobial resistance mechanisms, and current and future therapeutic procedures for endodontic biofilm is provided.

• Environmental Engineering Research
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• v.15 no.2
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• pp.71-78
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• 2010

To understand the effects of acclimation schemes on the formation of anode biofilms, different electrical performances are characterized in this study, with the roles of suspended and attached bacteria in single-chamber microbial fuel cells (MFCs). The results show that the generation of current in single-chamber MFCs is significantly affected by the development of a biofilm matrix on the anode surface containing abundant immobilized microorganisms. The long-term operation with suspended microorganisms was demonstrated to form a dense biofilm matrix that was able to reduce the activation loss in MFCs. Also, a Pt-coated anode was not favorable for the initial or long-term bacterial attachment due to its high hydrophobicity (contact angle = $124^{\circ}$), which promotes easy detachment of the biofilm from the anode surface. Maximum power ($655.0\;mW/m^2$) was obtained at a current density of $3,358.8\;mA/m^2$ in the MFCs with longer acclimation periods. It was found that a dense biofilm was able to enhance the charge transfer rates due to the complex development of a biofilm matrix anchoring the electrochemically active microorganisms together on the anode surface. Among the major components of the extracellular polymeric substance, carbohydrates ($85.7\;mg/m^2_{anode}$) and proteins ($81.0\;mg/m^2_{anode}$) in the dense anode biofilm accounted for 17 and 19%, respectively, which are greater than those in the sparse anode biofilm.

• Korean Journal of Microbiology
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• v.54 no.2
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• pp.167-168
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• 2018

Here we report the complete genome sequence of Staphylococcus xylosus S170, strong biofilm-producing strain, which comprised a single circular 2,910,005 bp chromosome and 32.97% G + C content. The genome included 2,674 protein-coding sequences, 22 rRNA genes, and 57 tRNA genes. Gene analysis of S. xylosus S170 could contribute to better understanding of biofilm-forming mechanisms.

• Journal of dental hygiene science
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• v.19 no.3
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• pp.162-169
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• 2019

Background: Oral diseases are caused by various systemic and local factors, the most closely related being the biofilm. However, the challenges involved in removing an established biofilm necessitate professional care for its removal. This study aimed to evaluate and compare the effects of professional self and professional biofilm care in healthy patients to prevent the development of periodontal diseases. Methods: Thirty-seven patients who visited the dental clinic between September 2018 and February 2019 were included in this study. Self-biofilm care was performed by routine tooth brushing and professional biofilm care was provided using the toothpick method (TPM) or the oral prophylaxis (OP) method using a rubber cup. Subgingival bacterial motility and halitosis (levels of hydrogen sulfide, $H_2S$; methyl mercaptan, $CH_3SH$; and di-methyl sulfide, $(CH_3)_2S$) were measured before, immediately after, and 5 hours after the preventive treatment in the three groups. Repeated measures analysis of variance test was performed to determine significant differences among the groups. Results: TPM was effective immediately after the prevention treatment, whereas OP was more effective after 5 hours (proximal surfaces, F=16.353, p<0.001; smooth surfaces, F=66.575, p<0.001). The three components responsible for halitosis were effectively reduced by professional biofilm care immediately after the preventive treatment; however, self-biofilm care was more effective after 5 hours ($H_2S$, F=3.564, p=0.011; $CH_3SH$, F=6.657, p<0.001; $(CH_3)_2S$, F=21.135, p<0.001). Conclusion: To prevent oral diseases, it is critical to monitor the biofilm. The dental hygienist should check the oral hygiene status and the ability of the patient to administer oral care. Professional biofilm care should be provided by assessing and treating each surface of the tooth. We hope to strengthen our professional in biofilm care through continuous clinical research.

• Korean Journal of Microbiology
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• v.50 no.2
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• pp.108-113
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• 2014

Pseudomonas aeruginosa and Vibrio vulnificus are Gram-negative human pathogens, which exert their virulence through quorum sensing (QS) regulation. The infection of these pathogens have been known to be mediated by biofilm formation in many cases and this study carried out the time-course analysis of biofilm formation depending on the QS regulation in P. aeruginosa and V. vulnificus. In P. aeruginosa, our results demonstrated that QS-deficient mutant better attached to surface at initial stage of biofilm formation, but poorly proceeded to the maturation of the biofilm structure, while wild type less attached at initial stage but developed highly structured biofilm at late stage. Because of this, the quantitative comparison of biofilm formation between wild type and the QS mutant showed the reversion; the QS mutant formed more biofilm until 10 h after inoculation than wild type, but wild type formed much more biofilm after 10 h than QS mutant. V. vulnificus has been reported to form more biofilm with the mutation on QS system. When we performed the same time-course analysis of the V. vulnificus biofilm formation, the reversion was not detected even with prolonged culture for 108 h and the QS mutant always forms more biofilm than wild type. These results indicate that the QS regulation negatively affects the attachment at early stage but positively facilitates the biofilm maturation at late stage in P. aeruginosa, while the QS regulation has a negative effect on the biofilm formation throughout the biofilm development in V. vulnificus. Based on our results, we suggest that the developmental stage of biofilm and bacterial species should be considered when the QS system is targeted for biofilm control.

• Journal of Microbiology and Biotechnology
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• v.28 no.5
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• pp.748-756
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• 2018

Biofilms are of vital significance in bioconversion and biotechnological processes. In this work, sugarcane molasses was used to enhance biofilms for the improvement of the production of fumigaclavine C (FC), a conidiation-associated ergot alkaloid with strong anti-inflammatory activities. Biofilm formation was more greatly induced by the addition of molasses than the addition of other reported biofilm inducers. With the optimal molasses concentration (400 g/l), the biofilm biomass was 6-fold higher than that with sucrose, and FC and conidia production was increased by 5.8- and 3.1-fold, respectively. Moreover, the global secondary metabolism regulatory gene laeA, FC biosynthetic gene fgaOx3, and asexual central regulatory genes brlA and wetA were upregulated in molasses-based biofilms, suggesting the upregulation of both asexual development and FC biosynthesis. This study provides novel insight into the stimulatory effects of molasses on biofilm formation and supports the widespread application of molasses as an inexpensive raw material and effective inducer for biofilm production.

• Journal of Physiology & Pathology in Korean Medicine
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• v.26 no.1
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• pp.74-80
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• 2012

Candida albicans is a common opportunistic pathogen and is frequently associated with biofilm formation occurring on the surfaces of host tissues and medical devices. On account of the distinct resistance of C. albicans biofilms to the conventional antifungal agents, new strategies are required to cope with these infections. The root of Polygonum cuspidatum has been used for medicinal purposes in East Asia. The aim of this study was to assess the anticandidal potential of the P. cuspidatum ethanol extract by evaluating biofilm formation, integrity of the cell membranes of C. albicans and adhesion of C. albicans cells to polystyrene surfaces. The growth and development of the biofilm was assessed using an XTT reduction assay, and the extract (0.39 mg/ml) significantly reduced ($41.1{\pm}17.8%$) biofilm formation of 11 C. albicans strains. The extract damaged the cell membranes of C. albicans and remarkably inhibited cell adhesion to polystyrene surfaces. The plant extract displayed fungistatic activity without significant hemolytic activity. Based on the results of this study, the P. cuspidatum extract has promising potential for use in treating biofilm-associated Candida infection.

• Korean Journal of Microbiology
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• v.52 no.1
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• pp.49-58
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• 2016

Compared to planktonic bacterial populations, biofilms have distinct bacterial community structures and play important ecological roles in various aquatic environments. Despite their ecological importance in nature, bacterial community structure and its succession during biofilm development in the Antarctic marine environment have not been elucidated. In this study, the succession of bacterial community, particularly during the early stage of biofilm development, in the Antarctic marine environment was investigated by pyrosequencing of the 16S rRNA gene. Overall bacterial distribution in biofilms differed considerably from surrounding seawater. Relative abundance of Gammaproteobacteria and Bacteroidetes which accounted for 78.9-88.3% of bacterial community changed drastically during biofilm succession. Gammaproteobacteria became more abundant with proceeding succession (75.7% on day 4) and decreased to 46.1% on day 7. The relative abundance of Bacteroidetes showed opposite trend to Gammaproteobacteria, decreasing from the early days to the intermediate days and becoming more abundant in the later days. There were striking differences in the composition of major OTUs (${\geq}1%$) among samples during the early stages of biofilm formation. Gammaproteobacterial species increased until day 4, while members of Bacteroidetes, the most dominant group on day 1, decreased until day 4 and then increased again. Interestingly, Pseudoalteromonas prydzensis was predominant, accounting for up to 67.4% of the biofilm bacterial community and indicating its important roles in the biofilm development.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.6
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• pp.767-777
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• 2012

Annular Biofilm Reactor (ABR) equipped with coupons of three different pipe materials (STS 304, PVC, PE) was used to generate drinking water biofilm samples. The level of assimilable organic carbon (AOC) during the sample generation period was $37.3{\mu}g/L$, and this level did not seem to be low enough to limit the formation of biofilm in this study. Terminal-restriction fragment length polymorphism (T-RFLP) analyses determined T-RF profile as early as 3 h of exposure on PVC coupons. Average surface roughness ($R_a$) measured by atomic force microscopic analyses was 125.7 nm for PVC, and this value was higher than for STS (71.6 nm) and PE (74.0 nm). However, biofilm formation was faster on STS (6 h) than on PE (12 h), which indicated that surface roughness might not be the only factor that controlled the initiation of biofilm development. Upon detection of the T-RF peaks, richness (S) and diversity indices such as Shannon (H) and Simpson (1/D) demonstrated a rather slow increase until 48 h followed by rapid increase regardless of the pipe materials. Differences of microbial community structures among the biofilm samples were determined based on the cluster analysis using Jaccard coefficients (Sj). Biofilm communities could be divided into two distinct groups according to the exposure time regardless of the pipe materials. First group contained a young (< 48 h) biofilm samples (10 out of 11) but second group contained a mature (${\geq}$ 48 h) samples (11 out of 14). Results suggested that, due to the complexity of biofilm, the targeting of the first group of cluster was crucial for optimizing the management of drinking water distribution systems and controlling microbial growth.