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.

Chlorhexidine has long been used in mouth washes for the control of dental caries, gingivitis and dental plaque. Minimal inhibitory concentration (MIC) is the lowest concentration of an antimicrobial substance to inhibit the growth of bacteria. Concentrations lower than the MIC are called sub minimal inhibitory concentrations (sub-MICs). Many studies have reported that sub-MICs of antimicrobial substances can affect the virulence of bacteria. The aim of this study was to investigate the effect of sub-MIC chlorhexidine on biofilm formation and coaggregation of oral early colonizers, such as Streptococcus gordonii, Actinomyces naeslundii and Actinomyces odontolyticus. The biofilm formation of S. gordonii, A. naeslundii and A. odontolyticus was not affected by sub-MIC chlorhexidine. However, the biofilm formation of S. mutans increased after incubation with sub-MIC chlorhexidine. In addition, cell surface hydrophobicity of S. mutans treated with sub-MIC of chlorhexidine, decreased when compared with the group not treated with chlorhexidine. However, significant differences were seen with other bacteria. Coaggregation of A. naeslundii with A. odontolyticus reduced by sub-MIC chlorhexidine, whereas the coaggreagation of A. naeslundii with S. gordonii remained unaffected. These results indicate that sub-MIC chlorhexidine could influence the binding properties, such as biofilm formation, hydrophobicity and coaggregation, in early colonizing streptococci and actinomycetes.

암반생물막의 군집구조와 생물량의 시, 공간적인 변화를 확인하기 위하여, 파도에 대한 노출이 다른 고사포와 격포에 서 11월부터 2011년 9월까지 격월로 암반조각을 채집하였다. 군집구조는 채집된 암반조각을 칫솔로 긁어 광학현미경 하에서 미세조류의 분류군별 개체수를 계수하여 분석하였고, 생물량은 NDVI, VI, 엽록소 a 농도를 측정하여 확인하였 다. 고사포와 격포의 조간대 암반생물막에서 가장 우점하는 분류군은 Aphanotece spp., Lyngbya spp.를 포함하는 남조류 였으며, 환경스트레스가 적은 조간대 하부에서는 규조류의 출현율이 높게 나타났다. 암반생물막에서 우점하는 규조류는 Navicula spp., Achnanthes spp.와 Licmophora spp.로 확인되었다. 식생지수와 엽록소 a 농도는 격포에 비해 고사포 생물막에서 높게 나타났다. 식생지수인 NDVI와 VI는 고사포에서 각각 0.49-0.40(평균 0.43), 2.64-3.22(평균 2.90)였으 며, 격포의 암반생물막은 NDVI와 VI가 각각 0.32-0.41(평균 0.38), 2.03-2.86(평균 2.48)으로 확인되었다. 엽록소 a의 농도는 고사포에서 12.79-32.87 ㎍/㎠(평균 22.84 ㎍/㎠)였고, 격포에서는 11.14-18.25 ㎍/㎠(평균 15.48 ㎍/㎠)로 식생지수와 마찬가지로 1월(겨울)에 최대, 3월(봄)에 최소인 계절 변화를 보였다. 엽록소 a 농도는 NDVI, VI와 양의 상관관계를 보여 비파괴적인 식생지수 측정방법이 파괴적인 엽록소 a 추출 방법을 대체할 수 있음을 알려준다. 결론적으 로 암반생물막은 여름보다 겨울에, 조간대 상부보다 중부와 하부에서, 파도에 보호된 해안보다 노출된 해안에서 높은 값을 보였다.

수처리용 분리막 시스템의 경우, 생물막 형성됨에 따라 분리막의 효율성이 저해된다. 이러한 문제를 완화 시키고자 생물막 형성을 방해하는 정족수 감지 억제 기술이 연구 되고 있다. 본 연구에서는 미생물의 내생기작과 외생기작을 각각 적용하여 생물막 저감 효과를 한 줄로 구성된 중공사막 모듈과 다발형 모듈에서 비교하였다. 그 결과 한 줄로 구성된 모듈에서는 내생기작과 외생기작이 미생물 생성 억제 성능에 큰 차이가 없었지만, 다발형 모듈에서는 외생 기작이 더 효과적인 것으로 나타났다. 따라서 다발형 모듈로 구성된 실제 중공사 수처 리 시스템에서는 외생 기작을 가진 정족수 감지 억제 미생물을 사용하여 분리 막 표면에 생기는 생물막을 저감하는 것이 내생 기작을 가진 미생물을 적용하는 것 보다 효율적인 것으로 보여진다.

Due to ever increasing trends in food safety, food manufacturers should take sanitary/ hygienic processing/packaging into key consideration. Minimizing the attachment of spoilage and pathogenic organisms to food contact surfaces and packaging materials is one of the major challenges in the fields of food science and biosafety. The bacteria adhering to the surface can produce subsequent hard-to-remove biofilms that potentially cause cross-contamination of processed foods. The contamination of spoilage to the food leads to shorten product shelf-life and, if foodborne pathogens are present, the consumption of contaminated food may possess a health hazard to consumers. In particular, a variety of surfaces in food packaging are vulnerable to development of biofilms as bacterial community is formed by adhering pathogens from native microflora in raw materialsfor prolonged contact time. It is now recognized that 80% of food outbreaks are related to biofilms. Therefore, inhibition of initial adhesion of biofilm-forming pathogenic cells on food contact surface is critically needed to minimize foodborne pathogen outbreaks.Bacterial adhesion is highly influenced by the substratum topography, i.e. roughness and porosity. Recent advancements in fabrication have made it possible to create well-organized nanofeatures (i.e. nanoporous and nanopillared) uniformly over a large surface area of a metal specimen. Nanosmooth (control) and nanoporous stainless steel foil surfaces were fabricated by precisely anodizing the degreased specimen in a 5% vol. of perchloric acid in anhydrous ethylene glycol. The applied voltage and anodization time were varied to obtain different pore diameters. The presences of 50 and 80 nm nanoporous patterns significantly inhibited the adhesion of L. monocytogenes by 2.0 to 2.3 log-cycles, depending on the pore diameters. It was found that nanoscale surface patterning and treatments are capable of enabling precise controls of molecular, physical, and biochemical interactions that govern bacterial adhesion to the solid substratum.

Cronobactersakazakii is a newly emerging high hazard pathogen, which causes encephalomeningitis and necrotic colitis. Recently, successful biocontrol of harmful microorganisms in several foods through the use of bacteriophages has been reported. In this study, bacteriophages were isolated from kimchi and sewages. Morphological analysis by TEM indicated that phages belonged to the Myoviridae family. In case of heat stability, KCES2 and ESP 2949-2 phages were susceptible to temperatures above 70oC. KCES2 and ESP 2949-2 phages inhibited the growth of C. sakazakii in culture broth. When KCES2 and ESP 2949-2 phages were applied to biofilm-formed C. sakazakii, C. sakazakii was efficiently reduced. Therefore, newly isolated KCES2 and ESP 2949-2 phage for C. sakazakii might effectively reduce C. sakazakii in various foods.

Minimal inhibitory concentration (MIC) is the lowest antibiotic concentration that inhibits the visible growth of bacteria. Sub-minimal inhibitory concentration (Sub-MIC) is defined as the concentration of an antimicrobial agent that does not have an effect on bacterial growth but can alter bacterial biochemistry, thus reducing bacterial virulence. Many studies have confirmed that sub-MICs of antibiotics can inhibit bacterial virulence factors. However, most studies were focused on Gram-negative bacteria, while few studies on the effect of sub-MICs of antibiotics on Gram-positive bacteria. In this study, we examined the influence of sub-MICs of doxycycline, tetracycline, penicillin and amoxicillin on biofilm formation and coaggregation of Streptococcus gordonii, Streptococcus mutans, Actinomyces naeslundii, and Actinomyces odontolyticus. In this study, incubation with sub-MIC of antibiotics had no effect on the biofilm formation of S. gordonii and A. naeslundii. However, S. mutans showed increased biofilm formation after incubation with sub-MIC amoxicillin and penicillin. Also, the biofilm formation of A. odontolyticus was increased after incubating with sub-MIC penicillin. Coaggregation of A. naeslundii with S. gordonii and A. odontolyticus was diminished by sub-MIC amoxicillin. These observations indicated that sub-MICs of antibiotics could affect variable virulence properties such as biofilm formation and coaggregation in Gram-positive oral bacteria.

Biofilms of oral microbes can cause various diseases in the oral cavity, such as dental caries, periodontitis and mucosal disease. Electrolyzed water generated by an electric current passed via water using a metal electrode has an antimicrobial effect on pathogenic bacteria which cause food poisoning. This study investigated the antimicrobial activity of electrolyzed waters using various metal electrodes on the floatage and biofilms of oral microbes. The electrolyzed water was generated by passing electric current using copper, silver and platinum electrodes. The electrolyzed water has a neutral pH. Streptococcus mutans, Porphyromonas gingivalis and Tannerella forsythia were cultured, and were used to form a biofilm using specific media. The floatage and biofilm of the microbes were then treated with the electrolyzed water. The electrolyzed water using platinum electrode (EWP) exhibited strong antimicrobial activity against the floatage and biofilm of the oral microbes. However, the electrolyzed water using copper and silver electrodes had no effect. The EWP disrupted the biofilm of oral microbes, except the S. mutans biofilm. Comparing the different electrolyzed waters that we created the platinum electrode generated water may be an ideal candidate for prevention of dental caries and periodontitis.

The purpose of this study was to assess the efficacy of photodynamic therapy (PDT) using erythrosine and a halogen light source to treat a biofilm formed on a machined surface titanium disk in vivo. Ten volunteers carried an acrylic appliance containing six machined surface titanium disks on the upper jaw over a period of five days. After the five days of biofilm formation period, the disks were removed. PDT using 20 μM erythrosine and halogen light was then applied to the biofilms formed on the disks. Experimental samples were divided into a negative control group (no erythrosine and no irradiation), E0 group (erythrosine 60s + no irradiation), E30 group (erythrosine 60s + halogen light 30s), and E60 group (erythrosine 60s + halogen light 60s). Following PDT, the bacteria in the biofilm were found to be detached from each disk. Each suspension with detached bacteria were diluted and cultivated on a blood-agar plate for five days under anaerobic conditions. The cultivated bacterial counts in the E60 group were significantly lower than the control group (86.4%) or E0 group (76.7%). In the experimental groups also, the light exposure time and bacterial counts showed a negative correlation. In conclusion, PDT using erythrosine and halogen light has bactericidal effects on biofilms formed on a titanium disk in vivo. Notably, applying 20 μM erythrosine and 60 seconds of halogen light irradiation had a significantly potent effect.

Bacillus cereus is widely distributed on various foods and is known to cause clinical infections, food poisoning toxin induced diarrhea and vomiting. In this study, B. cereus group detected and analyzed rice, rice bran, and biofilm characterization of B. cereus confirmed. B. cereus was identified in approximately 34.6% of brown rice and 50.0% of rice bran. B. thuringiensis was detected in 3.9% of brown rice and 23% of rice bran, and B. mycoides was isolated from rice bran. The microtiter plate assay detected differences in biofilm-forming ability among B. cereus group isolates. Biofilm of B. cereus seemed to increase the MIC values of antimicrobial agent and antibiotic compounds compared with planktonic cells. Therefore, sufficient attention should be given to good manufacturing practice and good agriculture practice to avoid contamination of B. cereus group raw material including rice.

The present study was conducted to investigate serotype distribution and biofilm formation of Actinobacillus (A.) pleuropneumoniae isolated from pneumonic lungs of pigs. A total of 37 A. pleuropneumoniae were isolated between January 2009 and June 2010. Serotypes of A. pleuropneumoniae isolates were determined using two different PCRs. The majority of isolates belonged to serotype 5 (n=31, 83.8%), and the others belonged to serotype 1 (n=4, 10.8%), and 2 (n=2, 5.4%), respectively. The ability of biofilm formation of the isolates was also determined by quantitative microtiter plate assay. Biofilm formation was observed in both 23 (62.2%) of the 37 field isolates and seven (43.8%) of the 16 reference strains. On the other hand, biofilm formation was various according to the serotypes: 20 (64.5%) of serotype 5, and three (75.0%) of serotype 1. However, two isolates of serotype 2 did not produce the biofilm in this study. Consequently, A. pleuropneumoniae serotype 5 was the most frequently detected (83.8% of the isolates), and 23 (62.2%) of 37 isolates exhibited biofilm positive phenotype in this study.

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.

In our present study, we investigated the effects of continentalic acid on Streptococcus mutans (S. mutans) biofilm. Methanol extract of Aralia continentalis (A. continentalis) was suspended in water and sequentially partitioned with CHCl3, ethyl acetate (EtOAc), and n-butanol (n-BuOH). The CHCl3 fraction showed the highest activity and an antibacterial compound against S. mutans was isolated from this preparation through various chromatography methods by bioassay guided fractionation. MS, 1H - NMR and 13C-NMR analysis showed that the active principle was continentalic acid which was confirmed to show significant inhibitory effects against S. mutans biofilm. These results may provide some scientific rationale for the traditional use these extracts for the treatment of dental diseases.

Denitrification activity of microbial communities in sand-gravel sediments and biofilms developing on a concrete riverbed of an urban small stream, Nogawa River, was measured monthly by laboratory incubations after the acetylene inhibition technique during une year from December 1987. The annual mean denitrification rate of the biofilm samples, 1.5 mgN m-2 h-1. was higtrer than the rate ut the sandgravel sediment samples. 0.8 mgN m-2 h-1. Contrary, ratios of the denitrified nitrogen to the total inorganic nitrogen fluxes was lower at the stretch where an attached microbial community developed un the concrete riverbed the stretch with sand-gravel riverbed. The longer residence times of water masses ut the site with a sand-gravel riverbed is responsible for the above relationship. Based on the average denitrifieation rates, if all the channel of Nogawa River were covered with concrete, the proportion of denitrified nitrogen to the input nitrogen should decrease to 1.3 %, whereas the ratio is 2.5% when the riverbed is composed of sands and gravel. The results suggest that the efficiency of nitrogen removal by benthic denitrification is strongly affected by the structure of a channel of the river.

In this study, we investigated the effects of indole on biofilm formation inhibition in Pantoea agglomerans (P. agglomerans). In the biofilm growth assay, indole inhibited biofilm formation across all the growth time. Depending on biofilm growth stage, indole exhibited biofilm inhibition and anti-bacterial effects on planktonic cells. Through the analysis of the proportion rate between biofilm and Colony Forming Units (CFU) and inhibition rate of indole, we confirmed that depending on the biofilm stage of P. agglomerans, indole treatment timing was more important than the treatment duration. By comparing gene expression rates through rt-qPCR P.agglomerans affected by indole was found to significantly change quorum sensing (pagI/R) and indole transportation (bssS) gene expressions. Throughout all, indole exhibited both antimicrobial and anti-biofilm effects on P. agglomerans. In addition, we confirmed the anti-biofilm effects of indole on mature biofilm. In conclusion, indole as a signal molecule, can exhibit anti-biofilm effects through bacterial quorum sensing inhibition and indole affects. Therefore, indole can regulate biofilm bacteria especially gram-negative opportunistic pathogens.

In this study, we investigated the in vitro anti-biofilm activities of plant extracts of chives (Allium tuberosum), garlic (Allium sativum), and radish (Raphanus sativus L.) against environment harmful bacteria (gram-positive Staphylococcus aureus and, gram-negative Salmonella typhimurium and Escherichia coli O157:H7). In the paper disc assay, garlic extracts exhibited the highest anti-biofilm activity. The Minimal Inhibitory Concentration (MIC) of all plant extracts was generally higher for gram-negative bacteria than it was for gram-positive bacteria. Gram-negative bacteria were more resistant to plant extracts. The tetrazolium dye (XTT) assay revealed that, each plant extract exhibited a different anti-biofilm activity at the MIC value depending on the pathogen involved. Among the plant extracts tested, garlic extracts (fresh juice and powder) effectively reduced the metabolic activity of the cells of food-poisoning bacteria in biofilms. These anti-biofilm activities were consistent with the results obtained through light microscopic observation. Though the garlic extract reduced biofilm formation for all pathogens tested, to elucidate whether this reduction was due to antimicrobial effects or anti-biofilm effects, we counted the colony forming units of pathogens in the presence of the garlic extract and a control antimicrobial drug. The garlic extract inhibited the E. coli O157:H7 biofilm effectively compared to the control antimicrobial drug ciprofloxacin; however, it did not inhibit S. aureus biofilm significantly compared to ciprofloxacin. In conclusion, garlic extracts could be used as natural food preservatives to prevent the growth of foodborne pathogens and elongater the shelf life of processed foods.

Haloacetic acids (HAAs) concentrations have been observed to decreased at drinking water distribution system extremities. This decrease is associated with microbiological degradation by pipe wall biofilm. The objective of this study was to evaluate HAAs degradation in a drinking water system in the presence of a biofilm and to identify the factors that influence this degradation. Degradation of monochloroacetic acid (MCAA), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) was observed in a simulated distribution system. The results obtained showed that different parameters came into play simultaneously in the degradation of HAAs, including retention time, water temperature, biomass, and composition of organic matter. Seasonal variations had a major effect on HAAs degradation and biomass quantity (ATP concentration) was lower by 25% in the winter compared with the summer.