• International Journal of Oral Biology
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• 제37권4호
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• pp.197-201
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• 2012

LIVE/DEAD$^{(R)}$ BacLight$^{TM}$ and alamarBlue$^{(R)}$ are fluorescent materials used for the enumeration of live and dead bacteria. LIVE/DEAD$^{(R)}$ BacLight$^{TM}$ is generally used for confocal microscopy applications to differentiate live from dead bacteria in a biofilm or planktonic state. AlamarBlue$^{(R)}$ has also been used widely to assay live and dead bacteria in a planktonic state. Whilst these materials are successfully utilized in experiments to discriminate live from dead bacteria for several species of bacteria, the application of these techniques to oral bacteria is limited to the use of LIVE/DEAD$^{(R)}$ BacLight$^{TM}$ in biofilm studies. In our present study, we assessed whether these two methods could enumerate live and dead oral bacterial species in a planktonic state. We tested the reagents on Streptococcus mutans, Streptococcus sobrinus, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans and Enterococcus faecalis and found that only LIVE/DEAD$^{(R)}$ BacLight$^{TM}$ could differentiate live from dead cells for all five of these oral strains. AlamarBlue$^{(R)}$ was not effective in this regard for P. gingivalis or A. actinomycetemcomitans. In addition, the differentiation of live and dead bacterial cells by alamarBlue$^{(R)}$ could not be performed for concentrations lower than $2{\times}10^6$ cells/ml. Our data thus indicate that LIVE/DEAD$^{(R)}$ BacLight$^{TM}$ is a more effective reagent for this analysis.

• Food Science and Biotechnology
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• 제16권2호
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• pp.315-319
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• 2007

Biofilm formation on various surfaces is a well-known phenomenon and it has caused pollution problems, health and safety hazards, and substantial economic loss in many areas including the food industry. In the present study, Gamma irradiation at a dose of 2.0 kGy reduced the bacterial counts of Staphylococcus aureus and Pseudomonas aeruginosa suspensions by 6.7 and >6.5 log CFU/mL, respectively, and 30 ppm of sodium hypochlorite effectively reduced the counts of both bacterial suspensions to below the limit of detection ($<2\;log\;CFU/cm^2$). However, in bacterial biofilms attached to stainless steel, gamma irradiation at a dose of 10.0 kGy reduced the counts of S. aureus attached fur 1 hr and overnight by ${\geq}5.1\;and\;5.0\;log\;CFU/cm^2$, respectively. Gamma irradiation at a dose of 1.0 kGy reduced the counts of P. aeruginosa counts to below the limit of detection ($<2\;log\;CFU/cm^2$). On the contrary, S. aureus and P. aeruginosa cells attached to stainless steel chips were difficult to eliminate using sodium hypochlorite. Four hundred ppm of sodium hypochlorite reduced the counts of S. aureus and P. aeruginosa attached for 1 hr by 2.5 and $3.3\;log\;CFU/cm^2$, respectively.

• Journal of Periodontal and Implant Science
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• 제49권5호
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• pp.319-329
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• 2019

Purpose: Direct application of atmospheric-pressure plasma jets (APPJs) has been established as an effective method of microbial decontamination. This study aimed to investigate the bactericidal effect of direct application of an APPJ using helium gas (He-APPJ) on Porphyromonas gingivalis biofilms on sandblasted and acid-etched (SLA) titanium discs. Methods: On the SLA discs covered by P. gingivalis biofilms, an APPJ with helium (He) as a discharge gas was applied at 3 different time intervals (0, 3, and 5 minutes). To evaluate the effect of the plasma itself, the He gas-only group was used as the control group. The bactericidal effect of the He-APPJ was determined by the number of colony-forming units. Bacterial viability was observed by confocal laser scanning microscopy (CLSM), and bacterial morphology was examined by scanning electron microscopy (SEM). Results: As the plasma treatment time increased, the amount of P. gingivalis decreased, and the difference was statistically significant. In the SEM images, compared to the control group, the bacterial biofilm structure on SLA discs treated by the He-APPJ for more than 3 minutes was destroyed. In addition, the CLSM images showed consistent results. Even in sites distant from the area of direct He-APPJ exposure, decontamination effects were observed in both SEM and CLSM images. Conclusions: He-APPJ application was effective in removing P. gingivalis biofilm on SLA titanium discs in an in vitro experiment.

• 자원환경지질
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• 제42권5호
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• pp.435-444
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• 2009

토양 입자 표면에 형성한 토착 미생물 바이오필름에 의하여 중금속을 흡착하므로써 하부 생태계로 이동하지 않고 원위치에 고정화하는 실험을 수행하였다. 토양으로 충진한 컬럼에 초산염, 유산염, 포도당 등의 탄소원을 10일간 공급함으로써 토양에 바이오필름을 형성하였다. 바이오필름 형성 기간 중, 초산염, 유산염, 포도당을 공급한 컬럼의 유출 수량은 탈이온수를 공급한 컬럼의 유출수량에 비하여 각각 98.5%, 97.3%, 94.7%인 것으로 나타났다. 이러한 유출수량의 감소는 형성된 바이오필름에 의한 토양 공극 폐색에 의한 것으로 판단된다. 바이오필름이 형성된 토양 컬럼에 Cd, Cr(VI), Cu, Pb, Zn 용액을 주입하며 시간에 따라 유출수를 채집, 중금속을 정량하였다. 바이오필름 컬럼을 통과하여 나온 유출수 중 Cd, Cr(VI), Cu, Zn 농도는 탈이온수 컬럼에 비하여 낮았으며, 이는 토양 입자에 비하여 바이오필름에 의한 이들 중금속 흡착 효율이 높기 때문인 것으로 여겨진다. 바이오필름에 의한 중금속 제거 효율은 토착 미생물에 공급한 탄소원의 종류에 따라 다르게 나타났다. 이러한 연구 결과는 중금속으로 오염된 토양 내에 중금속을 원위치 고정화하는 기술 개발에 유용하게 적용될 수 있을 것으로 기대한다.

• 생명과학회지
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• 제31권1호
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• pp.100-108
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• 2021

구강에는 700여 종의 미생물이 부유성 세균(planktonic cells)으로 있거나 치아 표면에 부착하여 바이오필름(biofilms)을 형성하고 있으며 구강 바이오필름(oral biofilms)과 관련된 대표적인 구강질환에는 치아우식증과 치주질환이 있다. 구강 세균은 타액의 흐름, 숙주의 항균 단백질, 영양소의 가용성 및 pH 변화, 항생제, 방부제 등의 영향을 받고 있지만 바이오필름이 형성되면 바이오필름은 물리적으로 두꺼운 층을 이루고 있기 때문에 구강 세균은 이와 같은 구강 내부의 환경적 스트레스에 저항할 수 있을 뿐만 아니라 외부 물질의 침투가 어렵고 바이오필름 내 세포간 상호작용을 통해 유전자 변이가 일어나기 때문에 부유성 세균보다 항생제에 대한 저항성이 1,000배 정도 높다. 따라서 구강 세균의 바이오필름 형성을 억제하거나 제거하면 보다 효과적으로 세균 감염에 의한 구강질환을 예방하거나 치료할 수 있을 것이다. 특히 구강 바이오필름은 여러 세균이 모여서 바이오필름을 형성하는 특징을 가지고 있기 때문에 세포간 신호전달체계인 정족수 감지(quorum sensing)는 구강 바이오필름을 제어할 수 있는 목표점이 될 수 있다. 이외에도 구강세균의 알칼리 생성 기질인 아르기닌을 이용하여 구강 미생물의 분포를 건강한 치아와 유사한 환경으로 전환하거나 S. mutans의 glucosyltransferase 분비를 억제하여 비수용성의 글루칸 형성을 억제함으로써 바이오필름 형성을 억제하는 방법도 구강 바이오필름을 제어할 수 있는 목표점이 될 수 있다. 이처럼 구강 내 병원성 세균의 사멸을 유도하기 보다는 구강 세균의 바이오필름 형성을 억제하거나 제거하는 방법은 치아우식증을 비롯한 구강질환을 선택적으로 예방하거나 치료할 수 있는 새로운 전략이 될 것이다.

• 한국습지학회지
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• 제9권1호
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• pp.115-121
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• 2007

A novel hydrogen fermentation technique by using polyvinyl alcohol (PVA) gel beads as a biomass carrier was investigated. The hydrogen gas was stably produced throughout the experimental period in a continuous reactor. Even though the hydrogen productivity was suddenly decrease by experimental troubles, the bacteria attached to the PVA gel beads played as an inoculum, it was promptly recovered. The hydrogen yield per glucose was not very high ($1.0-1.2mol-H_2/mol-glucose$), thus the optimization of the experimental conditions such as ORP and HRT should be considered to improve the hydrogen productivity. Bacterial community was stable during experimental period after the PVA gel beads applying, which indicated that applying of biomass carrier was specific to keep not only the biomass but also the bacteria commonly. Clostridium species were phylogenetically detected, which suggested that these bacteria contributed to the hydrogen production in the biofilm attached to the PVA gel beads.

• KSBB Journal
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• 제11권5호
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• pp.524-528
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• 1996

과립활성탄(GAC)상에 고정된 세균에 의한 4chloro-2-methylphenoxyacetic acid (MCPA)의 분해가 유통 조건하의 컬럼반응조에서 연구되었다. GAC상에 생물막을 형성시키기 위한 접종으로서 M MCPA를 분해하는 세균의 혼합배양이 사용되었다. 접종하기 전에 GAC에 의한 MCPA의 흡착을 조사 하였으며 접종후 GAC상에 형성된 생물막을 주사전자 현미경으로 관찰하였다. MCPA 분해는 생물막이 형성된 GAC를 포함하는 컬럼반응조의 회분 및 연 속운전 조건하에서 조사되었다. 회분배양에서 MC P PA의 완전분해가 이루어졌다. 연속배양상태에서 분적 인 MCPA의 분해가 일어났으나 분해정도는 기질인 MCPA의 결럼반응조내로 유입속도에 의존 었다.

• 자원환경지질
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• 제33권5호
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• pp.353-365
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• 2000

After their first appearance on Earth, bacteria have exerted significant influence on geochemical behavior of elements. Numerous evidence of their control on geochemistry through geologic history has been observed in a variety of natural environments. They have mediated weathering rate, formation of secondary minerals, redox transformation of metals and metalloids, and thus global cycling of elements. Such ability of bacteria receives so considerable attention from microbiologists, mineralogists, geologists, soil scientists, limnologists, oceanographers, and atmospheric scientists as well as geochemists that a new and interdisciplinary field of research called 'geomicrobiology' is currently expanding. Some recent subjects of geomicrobiology which are studied extensively are as follows: 1) Functional groups distributed on bacterial cell walls adsorb dissolved cations onto cell surfaces by electrostatic surface complexation, which is followed by hydrous mineral formation. 2) Dissimilatory metal reducing bacteria conserve energy to support growth by oxidation of organic matter coupled to reduction of some oxidized metals and/or metalloids. They can be effectively used in remediating environments contaminated with U, As, Se, and Cr. 3) Bacteria increase the rate of mineral dissolution by excreting proton and ligands such as organic acids into aqueous system. 4) Thorough investigation on the effects of biofilm on geochemical processes is needed, because most bacteria are adsorbed on solid substrates and form biofilms in natural settings.

• Environmental Engineering Research
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• 제24권1호
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• pp.17-23
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• 2019

This study monitored changes in the level of heterotrophic bacteria in the filtrate and investigated the effect of stagnant water on it, using a batch-operated, gravity-driven membrane system for household water treatment. The filtration test was carried out in the presence and absence of stagnant water in the filtrate line. The results showed that stagnant water accelerated the heterotrophic bacteria levels, measured by heterotrophic plate count, even though the heterotrophic plate count of the filtrate finally increased up to $10^5CFU/mL$ regardless of the presence of stagnant water. When the change in heterotrophic plate count of a batch was monitored over filtration time, heterotrophic plate count of the filtrate rapidly decreased within 5 min for each batch filtration. Biofilm formation on the filtrate line was observed in the presence of stagnant water. The biofilm fully covered the filtrate line and contained numerous microorganisms. During storage after filtration, heterotrophic plate count increased exponentially. To improve the filtrate quality of a filtration-based household water treatment system, therefore, the stagnant water in the filtrate line should be minimized, the filtrate produced at the first 5 min is recommended not to be used as potable water, and the storage of filtrate should be avoided.

• 한국물환경학회지
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• 제38권4호
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• pp.171-176
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• 2022

Recently, an autotrophic single-stage nitrogen removal (ASSNR) process based on the anaerobic ammonium oxidation (ANAMMOX) reaction has been proven as an economical ammonia treatment. It is highly evident that double-layered gel beads are a promising alternative to the natural biofilm for ASSNR because of the high mechanical strength of poly(vinyl alcohol) (PVA)/alginate structure and efficient protection of ANAMMOX bacteria from dissolved oxygen (DO) due to the thick outer layer. However, the thick outer layer results in severe mass transport limitation and consequent lowered bacterial activity. Therefore, the effects of the thickness of the outer layer on the overall reaction rate were tested in the biofilm model using AQUASIM for ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB) and ANAMMOX bacteria. A thickness of 0.5~1.0 mm is preferred for the maximum total nitrogen (TN) removal. In addition, a DO of 0.5 mg/L resulted in the best total nitrogen removal. A higher DO induces NOB activity and consequent lower TN removal efficiency. The optimal density of AO B and NO B density was 1~10% for a 10% ANAMMOX bacterial in the double-layered PVA/alginate gel beads. The real effects of operating parameters of the thickness of the outer layer, DO and concentrations of biomass balance should be intensively investigated in the controlled experiments in batch and continuous modes.