• Journal of Microbiology and Biotechnology
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• 제26권9호
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• pp.1593-1604
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• 2016

Recently, bacterial quorum quenching (QQ) has been proven to have potential as an innovative approach for biofouling control in membrane bioreactors (MBRs) for advanced wastewater treatment. Although information regarding the microbial community is crucial for the development of QQ strategies, little information exists on the microbial ecology in QQ-MBRs. In this study, the microbial communities of biofilm were investigated in relation to the effect of QQ on anoxic/oxic MBRs. Two laboratory-scale MBRs were operated with and without QQ-beads (QQ-bacteria entrapped in beads). The transmembrane pressure increase in the QQ-MBRs was delayed by approximately 100-110% compared with conventional- and vacant-MBRs (beads without QQ-bacteria) at 45 kPa. In terms of the microbial community, QQ gradually favored the development of a diverse and even community. QQ had an effect on both the bacterial composition and change rate of the bacterial composition. Proteobacteria and Bacteroidetes were the most dominant phyla in the biofilm, and the average relative composition of Proteobacteria was low in the QQ-MBR. Thiothrix sp. was the dominant bacterium in the biofilm. The relative composition of Thiothrix sp. was low in the QQ-MBR. These findings provide useful information that can inform the development of a new QQ strategy.

• Journal of Microbiology and Biotechnology
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• 제21권2호
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• pp.115-123
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• 2011

To investigate the effects of pipe materials on biofilm accumulation and water quality, an annular reactor with the sample coupons of four pipe materials (steel, copper, stainless steel, and polyvinyl chloride) was operated under hydraulic conditions similar to a real plumbing system for 15 months. The bacterial concentrations were substantially increased in the steel and copper reactors with progression of corrosion, whereas those in stainless steel (STS) and polyvinyl chloride (PVC) reactors were affected mainly by water temperature. The heterotrophic plate count (HPC) of biofilms was about 100 times higher on steel pipe than other pipes throughout the experiment, with the STS pipe showing the lowest bacterial number at the end of the operation. Analysis of the 16S rDNA sequences of 176 cultivated isolates revealed that 66.5% was Proteobacteria and the others included unclassified bacteria, Actinobacteria, and Bacilli. Regardless of the pipe materials, Sphingomonas was the predominant species in all biofilms. PCR-DGGE analysis showed that steel pipe exhibited the highest bacterial diversity among the metallic pipes, and the DGGE profile of biofilm on PVC showed three additional bands not detected from the profiles of the metallic materials. Environmental scanning electron microscopy showed that corrosion level and biofilm accumulation were the least in the STS coupon. These results suggest that the STS pipe is the best material for plumbing systems in terms of the microbiological aspects of water quality.

• 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.

• Journal of Microbiology and Biotechnology
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• 제24권1호
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• pp.8-12
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• 2014

Biofilm formation and antibiotic resistance are important determinants for bacterial pathogenicity. Ribonucleases control RNA degradation and there is increasing evidence that they have an important role in virulence mechanisms. In this report, we show that ribonucleases affect susceptibility against ribosome-targeting antibiotics and biofilm formation in Salmonella.

• 생태와환경
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• 제37권3호통권108호
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• pp.297-303
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• 2004

수서 생태계에서 생물막 성장을 고찰하기 위해 2차원 셀룰라오토마톤 (CA) 모델을 구현하였다. 영양물 농도와 연계하여 CA의 단순한 지역 규칙을 세균 개체군의 성장을 나타내는데 적용하였다. 초기 세균 분포는 낮은 영양물 농도에서 개체군 크기와 생물막 형태를 결정하는데 중요한 역할을 하였다. 집중분포에서는 균일분포나 마구잡이분포에 비해 개체군 크기가 느리게 증가하였다. 반면 공극률은 다른 초기 분포에 비해 균일분포에서 높게 나타나는 경향을 보였다.

• 한국미생물·생명공학회지
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• 제44권4호
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• pp.535-539
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• 2016

제주도 넙치 양식장에서 주로 발생하는 어류질병세균인 S. parauberis, S. iniae, E. tarda에 대한 피해를 줄이고자 갈륨을 이용하여 어류질병세균을 억제하고자 한다. 본 연구진은 Sp, Si, Et의 생육도와 biofilm 형성능을 확인하였으며, 세균의 성장도와 biofilm 형성능간의 특정한 패턴은 없었으며 세균의 성장도가 높다 하더라도 biofilm을 활발히 형성하지 않음을 알 수 있었다. 어류질병세균이 형성하는 biofilm을 저해하기 위해 갈륨을 2.0, 4.0, 8.0 mg/ml로 첨가하여 저해능을 확인한 결과 72시간째 biofilm의 형성이 크게 저해되는 것을 확인하였다. 또한 biofilm을 저해하는 동시에 균주의 사멸능을 확인하기 위해 resazurin assay와 propidium iodide를 이용하여 염색한 결과 갈륨의 농도에 따라 균주의 사멸이 증가하는 것을 확인하였다. 이에 따라 in vitro 상에서 갈륨이 어류질병세균의 biofilm을 억제하는 동시에 균주를 사멸시키는 물질로서 가치가 있다고 사료된다.

• 상하수도학회지
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• 제36권2호
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• pp.97-106
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• 2022

Recently microplastic (MP) biofilm is being attracted as an important environmental issue because it can act as a pollutant carrier in aqueous system. Therefore, this study investigated the MP biofilm communities originated from freshwater. The results showed the bacterial community structure of MP biofilm was distinctively different from the freshwater regardless of biofilm-forming condition and MP type. For MP biofilm communities exposed to raw freshwater, Solimonas variicoloris-like microbe, Frigidibacter albus-like microbe, Nitrospirillum amazonense-like microbe, and Pseudochroococcus couteii-like microbe became abundant, while Acinetobacter johnsonii, Macellibacteroides fermentans, and Sedimentibacter acidaminivorans-like microbe were found as major bacteria for MP biofilm communities exposed to organic rich condition. The results of this study suggest that the unique freshwater biofilm community could be formed on the MP surface.

• The Plant Pathology Journal
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• 제33권6호
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• pp.602-607
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• 2017

Segregation and condensation protein B (ScpB) is essential for replication and segregation in living organisms. Here, we reported the functions of ScpBXv (ScpB-like protein in Xanthomonas campestris pv. vesicatoria) using phenotypic and proteomic analyses. Growth of $Xcv{\Delta}scpBXv$ (ScpBXv knockout mutant) was reduced under both slow and fast growth conditions in rich medium, but comparable to this of the wild-type in plant-mimic conditions. Interestingly, the mutant was significantly less virulent than the wild-type in tomato, indicating that ScpBXv is involved in virulence. To investigate ScpBXv-associated mechanisms, comparative proteomic analyses were carried out and the abundance of 187 proteins was altered. Among them, diverse transcriptional regulators involved in biofilm formation and virulence were abundant in the wild-type. We further showed that biofilm formation of $Xcv{\Delta}scpBXv$ was reduced. This study provides new insights into the functions of ScpBXv in bacterial replication and biofilm formation, which may contribute to the virulence of Xcv.

• 한국미생물·생명공학회지
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• 제23권4호
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• pp.492-498
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• 1995

Net type polyvinylidene chloride (PVDC) media and cillium type polyethlene polypropylene (PEPP) media were installed in the aereted submerged biofilm reactors. Synthetic phenol wastewater for feed were made to contain 1,480 mg of phenol per liter of water. The organic loading range of reactors were 0.439-0.456 kg COD/m$_{3}$, 0.882 - 0.919 kg COD/m$_{3}$ and 1.199-1.339 kg COD/m$_{3}$. Comparing PVDC to PEPP media, the bacterial number found in biofilm on PEPP were slightly higher. With the low temperature (10$\circ$C), the number of bacteria was some what deceered. Number of bacterial strains identified from PVDC were 23 and those from PEPP were 42. Genera identified in the PVDC media were Flavobacterium (47.8%), Unidentified (17.6%), Pseudomonas (13.0%), Micrococcus (8.7%) and Beggratoa (8.7%). Genera identified in the PEPP media reactor were Pseudomonas (35.7%), Alcaligenes (19.0%), Aeromonas (14.33%) and Micrococcus (11.9%), In the steady, state, a filamentous bacteria, type 1701 was identified in all of the reactors. Paramecium sp. and fungi were present in the PVDC media reactor. While, Difflugia sp, Paramecium sp. and fungi were found in the PEPP media reactor. The low diversity of protozoa was ascribed to high concentration of phenol.

• Journal of Periodontal and Implant Science
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• 제48권6호
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• pp.373-382
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• 2018

Purpose: The aim of this study was to evaluate the effects of various prophylactic treatments of titanium implants on bacterial biofilm formation, correlating surface modifications with the biofilms produced by Pseudomonas aeruginosa PAO1, Staphylococcus aureus, and bacteria isolated from saliva. Methods: Pure titanium disks were treated with various prophylactic procedures, and atomic force microscopy (AFM) was used to determine the degree to which surface roughness was modified. To evaluate antibiofilm activity, we used P. aeruginosa PAO1, S. aureus, and saliva-isolated Streptococcus spp., Bacteroides fragilis, and Staphylococcus epidermidis. Results: AFM showed that the surface roughness increased after using the air-polishing device and ultrasonic scaler, while a significant reduction was observed after using a curette or polishing with Detartrine ZTM (DZ) abrasive paste. In addition, we only observed a significant (P<0.01) reduction in biofilm formation on the DZ-treated implant surfaces. Conclusion: In this study, both AFM and antibiofilm analyses indicated that using DZ abrasive paste could be considered as the prophylactic procedure of choice for managing peri-implant lesions and for therapy-resistant cases of periodontitis.