• International Journal of Oral Biology
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• v.37 no.4
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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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• v.16 no.2
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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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• v.49 no.5
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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.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.435-444
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• 2009

In situ stabilization of heavy metals through adsorption onto indigenous bacterial biofilm developed on soil particles was investigated. Biofilms were developed in soil columns by supply of various carbon sources such as acetate, lactate and glucose. During development of biofilms, acetate, lactate, and glucose solutions were flew out from the soil columns with volume ratios of 98.5%, 97.3%, and 94.7%, respectively, when compared with soil column supplied with deionized water. Decrease in effluent amounts through the soil columns amended with carbon sources over time indicated the formation of biofilms resulting in decrease of soil porosity. Solutions of Cd, Cr(VI), Cu, Pb, and Zn were injected into the biofilms supported on soil particles in the columns, and the dissolved heavy metals in effluents were determined. Concentrations of dissolved Cd, Cr(VI), Cu, and Zn in the effluents through biofilm columns were lower than those of control column supplied with deionized water. The result was likely due to enhanced adsorption of the metals onto biofilms. Efficiency of metal removal by biofilms depended on the type of carbon sources supplied. The enhanced removal of dissolved heavy metals by bacterial biofilms in this study may be effectively applied to technical development of in situ stabilization of heavy metals in natural soil formation contaminated with heavy metals.

• Journal of Life Science
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• v.31 no.1
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• pp.100-108
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• 2021

In the oral cavity, there are hundreds of microbial species that exist as planktonic cells or are incorporated into biofilms. The accumulation and proliferation of pathogenic bacteria in the oral biofilm can lead to caries and periodontitis, which are typical oral diseases. The oral bacteria in the biofilm not only can resist environmental stress inside the oral cavity, but also have a 1,000 times higher resistance to antibiotics than planktonic cells by genes exchange through the interaction between cells in the oral biofilm. Therefore, if the formation of oral biofilm is suppressed or removed, oral diseases caused by bacterial infection can be more effectively prevented or treated. In particular, since oral biofilms have the characteristic of forming a biofilm by gathering several bacteria, quorum sensing, a signaling system between cells, can be a target for controlling the oral biofilm. In addition, a method of inhibiting biofilm formation by using arginine, an alkali-producing substrate of oral bacteria, is used to convert the distribution of oral microorganisms into an environment similar to that of healthy teeth or inhibit the secretion of glucosyltransferase by S. mutans to inhibit the formation of non-soluble glucans. It can be a target to control oral biofilm. This method of inhibiting or removing the oral biofilm formation rather than inducing the death of pathogenic bacteria in the oral cavity will be a new strategy that can selectively prevent or therapeutic avenues for oral diseases including dental caries.

• Journal of Wetlands Research
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• v.9 no.1
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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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• v.11 no.5
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• pp.524-528
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• 1996

Bacterial degradation of 4-chloro-2-methylphenoxyacetic acid (MCPA) was studied in column reactors under conditions approximating a fluidized bed system, with granular activated carbon (GAC) as a support matrix. A mixed bacterial culture of MCPA-degrading bacteria was used as an inoculum to develop a biofilm on GAC. Initially, adsorption of MCPA by GAC and blofilm formation on GAC were examined. MCPA degradation was evaluated with a batch and continuous mode of operation of the GAC fixed-film column reactors. In the batch operations, complete degradation of MCPA was achieved during the incubation period. Partial degradation of MCPA occurred in the continuous operations and MCPA degradation was dependent on the feeding rate of MCPA solution.

• Economic and Environmental Geology
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• v.33 no.5
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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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• v.24 no.1
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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.

• Journal of Korean Society on Water Environment
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• v.38 no.4
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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.