• 대한환경공학회지
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• 제31권4호
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• pp.308-323
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• 2009

생물활성탄 공정은 정수처리에서 획기적인 공정으로 평가받고 있으며, 전 세계적으로 많은 정수장에서 BAC 공정을 채택하여 운전하고 있다. BAC 공정의 장점은 활성탄에 흡착된 오염물질들이 활성탄 표면에서 서식하고 있는 다양한 미생물 집합체(생물막)에 의해 생물분해되어 자연적으로 활성탄의 재생이 이루어져 활성탄 사용기간의 연장을 유도하여 정수처리 비용을 감소시킬 수 있다는 것이다. 또한, 유입수중의 생분해 가능한 유기물질들을 제거하여 배 급수관망에서 미생물의 재성장을 억제하는데 탁월하다. 그러나 BAC 공정의 효율이 활성탄 표면에 형성되어 있는 생물막에 의해 제한되어지는 문제점도 있다. 본 논문에서는 GAC에서 BAC로의 전환, BAC 생물막의 특성, 오염물질의 제거 메카니즘, BAC 공정에 영향을 미치는 인자들, BAC 공정의 제어 및 BAC 공정의 모델링에 대해 크게 여섯 부분으로 상세하게 기술하였다.

• International Journal of Oral Biology
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• 제41권4호
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• pp.253-262
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• 2016

Streptococcus mutans (S. mutans) is one of the most important bacteria in the formation of dental plaque and dental caries. S. mutans adheres to an acquired pellicle formed on the tooth surface, and aggregates with many oral bacteria. It initiates plaque formation by synthesizing glucan from sucrose, which is catalyzed by glucosyltransferases. Propolis is a resinous mixture produced by honeybees, by mixing saliva and beeswax with secretions gathered from wood sap and flower pollen. Bees prevent pathogenic invasions by coating the propolis to the outer and inner surface of the honeycomb. Propolis has traditionally been used for the treatment of allergic rhinitis, asthma and dermatitis. We investigated the inhibitory effects of propolis ethanol extract on biofilm formation and gene expression of S. mutans. The biofilm formation of S. mutans was determined by scanning electron microscopy (SEM) and safranin staining. We observed that the extract of propolis had an inhibitory effect on the formation of S. mutans biofilms at concentrations higher than 0.2 mg/ml. Real-time PCR analysis showed that the gene expression of biofilm formation, such as gbpB, spaP, brpA, relA and vicR of S. mutans, was significantly decreased in a dose dependent manner. The ethanol extract of propolis showed concentration dependent growth inhibition of S. mutans, and significant inhibition of acid production at concentrations of 0.025, 0.05, 0.1 and 0.2 mg/ml, compared to the control group. These results suggest that the ethanol extract of propolis inhibits gene expression related to biofilm formation in S. mutans.

• Journal of Microbiology and Biotechnology
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• 제27권3호
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• pp.542-551
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• 2017

Small phytochemicals have been successfully adopted as antibacterial chemotherapies and are being increasingly viewed as potential antibiofilm agents. Some of these molecules are known to repress biofilm and toxin production by certain bacterial and yeast pathogens, but information is lacking with regard to the genes allied with biofilm formation. The present study was performed to investigate the inhibitory effect of burdock root extract (BRE) and of chlorogenic acid (CGA; a component of BRE) on clinical isolates of Klebsiella pneumoniae. BRE and CGA exhibited significant antibiofilm activity against K. pneumoniae without inflicting any harm to its planktonic counterparts. In vitro assays supported the ${\beta}$-lactamase inhibitory effect of CGA and BRE while in silico docking showed that CGA bound strongly with the active sites of sulfhydryl-variable-1 ${\beta}$-lactamase. Furthermore, the mRNA transcript levels of two biofilm-associated genes (type 3 fimbriae mrkD and trehalose-6-phosphate hydrolase treC) were significantly downregulated in CGA- and BRE-treated samples. In addition, CGA inhibited biofilm formation by Escherichia coli and Candida albicans without affecting their planktonic cell growth. These findings show that BRE and its component CGA have potential use in antibiofilm strategies against persistent K. pneumoniae infections.

• 한국물환경학회지
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• 제22권3호
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• pp.566-571
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• 2006

A sequencing batch biofilm reactor (SBBR) operated with a cycle of anaerobic - aerobic - anoxic - aerobic has been evaluated for the nutrient removal characteristics. The sponge-like moving media was filled to about 10% of reactor volume. The sewage was the major substrate while external synthetic carbon substrate was added to the anoxic stage to enhance the nitrogen removal. The operational results indicated that maximum T-N and T-P removal efficiencies were 97% and 94%, respectively were achieved, while COD removal of 92%. The observations of significant nitrogen removal in the first aerobic stage indicated that nitrogen removal behaviour in this SBBR was different to conventional SBR. Although the reasons for aerobic nitrogen removal has speculated to either simultaneous nitrification and denitrification or anoxic denitrification inside of the media, further researches are required to confirm the observation. The specific oxygen uptake rate (SOUR) test with biofilm and suspended growth sludge indicated that biofilm in SBBR played a major role to remove substrates.

• 대한기계학회논문집B
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• 제36권11호
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• pp.1119-1126
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• 2012

세균의 집단 행동은 생물막의 형성에 중요한 역할을 하고 있다. 본 연구에서는 대장균(E. coli) 및 고초균(B. subtilis) 군집에서 형성된 유동성 생물막의 유체역학적 특성을 비교하고자 초기에 아가 플레이트 내에서 층을 이루다가 성장하는 군집 표면 위로 자발적으로 분포되는 200 nm의 형광입자를 가시화 하였다. 대장균 군집에서는 유동하지 않는 200 nm 크기의 형광입자를 이용하여 성장하는 세균 군집의 3차원 형상 프로파일을 측정하였다. 고초균 군집의 경계에서 나타나는 와류 패턴은 고초균이 분비하는 계면활성제 내에서 유동하는 형광입자를 추적하여 가시화하였다. 본 연구는 세균의 생리 기능을 조절하는 새로운 물리적인 요소를 밝혀내고 세균의 증식 및 군집 이동에 영향을 미치는 유동성 생물막의 효과를 파악하는 첫걸음이 될 것이다.

• Journal of Microbiology and Biotechnology
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• 제23권8호
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• pp.1070-1075
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• 2013

Streptococcus mutans is the primary etiological agent of dental caries. The antimicrobial peptide $\small{D}$-Nal-Pac-525 was designed by replacing the tryptophans of the Trp-rich peptide Pac-525 with $\small{D}$-${\beta}$-naphthyalanines. To assess the effect of $\small{D}$-Nal-Pac-525 on cariogenic bacteria, the activity of $\small{D}$-Nal-Pac-525 on the growth of S. mutans and its biofilm formation were examined. $\small{D}$-Nal-Pac-525 showed robust antimicrobial activity against S. mutans (minimum inhibitory concentration of 4 ${\mu}g/ml$). Using scanning electron microscopy and transmission electron microscopy, it was shown that $\small{D}$-Nal-Pac-525 caused morphological changes and damaged the cell membrane of S. mutans. $\small{D}$-Nal-Pac-525 inhibited biofilm formation of S. mutans at 2 ${\mu}g/ml$. The results of this study suggest that $\small{D}$-Nal-Pac-525 has great potential for clinical application as a dental caries-preventing agent.

• Journal of Microbiology and Biotechnology
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• 제32권2호
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• pp.263-267
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• 2022

The aim of this study was to determine whether the antibacterial activity of chitosan-modified Fe₃O₄ (CS@Fe₃O₄) nanomaterials against Acinetobacter baumannii (A. baumannii) is mediated through changes in biofilm formation and reactive oxygen species (ROS) production. For this purpose, the broth dilution method was used to examine the effect of CS@Fe₃O₄ nanoparticles on bacterial growth. The effects of CS@Fe₃O₄ nanoparticles on biofilm formation were measured using a semi-quantitative crystal violet staining assay. In addition, a bacterial ROS detection kit was used to detect the production of ROS in bacteria. The results showed that CS@Fe₃O₄ nanoparticles had a significant inhibitory effect on the colony growth and biofilm formation of drug-resistant A. baumannii (p < 0.05). The ROS stress assay revealed significantly higher ROS levels in A. baumannii subjected to CS@Fe₃O₄ nanoparticle treatment than the control group (p < 0.05). Thus, we demonstrated for the first time that CS@Fe₃O₄ nanoparticles had an inhibitory effect on A. baumannii in vitro, and that the antibacterial effect of CS@Fe₃O₄ nanoparticles on drug-resistant A. baumannii was more significant than on drug-sensitive bacteria. Our findings suggest that the antibacterial mechanism of CS@Fe₃O₄ nanoparticles is mediated through inhibition of biofilm formation in drug-resistant bacteria, as well as stimulation of A. baumannii to produce ROS. In summary, our data indicate that CS@Fe₃O₄ nanoparticles could be used to treat infections caused by drug-resistant A. baumannii.

• 치위생과학회지
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• 제23권2호
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• pp.103-111
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• 2023

Background: Some studies confirm the reduction of the number of Streptococcus mutans in saliva and dental plaque by Lactobacillus, however, these effects are not always confirmed in in vitro and clinical studies, and only the risk of dental caries has been reported. Our in vitro study aimed to reveal microbial and biochemical changes in the single cultures of S. mutans, Lactobacillus casei and Aggregatibactor actinomycetemcomitans and co-cultures of S. mutans and L. casei or A. actinomycetemcomitans according to sucrose concentration. We also aimed to confirm the anti-oral bacterial and anti-biofilm activities of L. casei and A. actinomycetemcomitans against S. mutans according to sucrose concentration. Methods: S. mutans (KCCM 40105), L. casei (KCCM 12452), and A. actinomycetemcomitans (KCTC 2581) diluted to 5×10⁶ CFU/ml were single cultured, and L. casei or A. actinomycetemcomitans applied at concentrations of 10%, 20%, 30% and 40% to S. mutans were co-cultured with selective medium containing 0%, 1% and 5% sucrose at 36.5℃ for 24 hours. Measurements of bacterial growth value and acid production, disk diffusion and biofilm formation assays were performed. Results: In the medium containing sucrose, the bacterial growth and biofilm formation by S. mutans, L. casei, and A. actinomycetemcomitans were increased. In contrast, 30% and 40% of L. casei in the medium containing 0% sucrose showed both anti-oral bacterial and anti-biofilm activities. This implies that L. casei can be used as probiotic therapy to reduce S. mutans in a 0% sucrose environment. Conclusion: The concentration of sucrose in the oral environment is important for the control of pathogenic bacteria that cause dental caries and periodontitis. To apply probiotic therapy using L. casei for S. mutans reduction, the concentration of sucrose must be considered.

• 대한소아치과학회지
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• 제46권2호
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• pp.135-138
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• 2019

이 연구의 목적은 부유 및 바이오필름 상태의 Mutans streptococci에서 치태와 치석 착색제로 치과 진료실에서 사용하는 식용색소인 에리스로신에 대한 감수성을 조사하는 것이다. 세균은 호기성 조건에 배양하였고, 에리스로신은 $0.02-10000{\mu}g/L$의 농도로 희석하였다. 부유 상태 S. mutans의 최소 억제 농도(MIC)와 최소 살균 농도(MBC)를 측정하였다. 세균을 배양하여 바이오필름을 형성한 후, 최소 바이오필름 억제 농도(MBIC) 및 최소 바이오필름 박멸 농도(MBEC)를 측정하였다. MIC와 MBC는 $19.5{\mu}g/L$로 동일하게 측정되었으며 따라서 에리스로신은 부유 상태의 S. mutans에 대해 살균 효과를 가지는 것으로 나타났다. MBIC, MBEC 값은 각각 $313{\mu}g/L$, $2500{\mu}g/L$로 측정되었다. 측정된 MIC, MBC, MBIC는 실제로 치과에서 사용되는 농도에 비해 낮은 값이며 따라서 인체에 무해한 농도에서 S. mutans를 억제할 수 있을 것으로 보인다.

• The Plant Pathology Journal
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• 제39권1호
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• pp.123-135
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• 2023

Previously, Pseudomonas plecoglossicida YJR13 and Pseudomonas putida YJR92 from a sequential screening procedure were proven to effectively control Phytophthora blight caused by Phytophthora capsici. In this study, we further investigated the anti-oomycete activities of these strains against mycelial growth, zoospore germination, and germ tube elongation of P. capsici. We also investigated root colonization ability of the bacterial strains in square dishes, including cell motility (swimming and swarming motilities) and biofilm formation. Both strains significantly inhibited mycelial growth in liquid and solid V8 juice media and M9 minimal media, zoospore germination, and germ tube elongation compared with Bacillus vallismortis EXTN-1 (positive biocontrol strain), Sphingomonas aquatilis KU408 (negative biocontrol strain), and MgSO₄ solution (untreated control). In diluted (nutrient-deficient) V₈ juice broth, the tested strain populations were maintained at >10⁸ cells/ml, simultaneously providing mycelial inhibitory activity. Additionally, these strains colonized pepper roots at a 10⁶ cells/ml concentration for 7 days. The root colonization of the strains was supported by strong swimming and swarming activities, biofilm formation, and chemotactic activity towards exudate components (amino acids, organic acids, and sugars) of pepper roots. Collectively, these results suggest that strains YJR13 and YJR92 can effectively suppress Phytophthora blight of pepper through direct anti-oomycete activities against mycelial growth, zoospore germination and germ tube elongation. Bacterial colonization of pepper roots may be mediated by cell motility and biofilm formation together with chemotaxis to root exudates.