• Korean Journal of Microbiology
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• v.47 no.2
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• pp.167-169
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• 2011

The Saccharomyces cerevisiae S288c strain does not show haploid and diploid filamentous growth, and biofilm formation, because it has a flo8 nonsense mutation unlike ${\Sigma}1278b$ strain which has a FLO8 gene. During the heat stress experiments to investigate the role of ScKns1, LAMMER kinase in S. cerevisiae, we found that ${\Sigma}1278b$ strain revealed heat sensitivity at $37^{\circ}C$, a mild heat stress in contrast to S288c strain. We also found that the disruption of ScKns1 and the addition of sorbitol suppress heat sensitivity of ${\Sigma}1278b$ strain. These results suggest the possibility that Flo8 and ScKns1 may interact to transducer a signal for regulating heat stress through a novel signaling pathway.

• Korean Journal of Microbiology
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• v.46 no.1
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• pp.1-8
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• 2010

New technologies are providing unprecedented knowledge into microbial community structure and functions. Even though nucleic acid based approaches provide a lot of information, metaproteomics could provide a high-resolution representation of genotypic and phenotypic traits of distinct microbial communities. Analyzing the metagenome from different microbial ecosystems, metaproteomics has been applied to seawater, human guts, activated sludge, acid mine drainage biofilm, and soil. Although these studies employed different approaches, they elucidated that metaproteomics could provide a link among microbial community structure, function, physiology, interaction, ecology, and evolution. These approaches are reviewed here to help gain insights into the function of microbial community in ecosystems.

• Journal of Environmental Science International
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• v.8 no.4
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• pp.525-532
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• 1999

This study was conducted to evaluate capability of dyeing wastewater treatment for 3 type reactors. These reactors were Packed Bed Reactor(PBR), Fluidized Bed reactor(FBR) and Moving Media Complete Mixing Activated Sludge reactor(MMCMAS). Experiments of PBR and FBR were performed by various packing ratios and organic loading rates, experiments of MMCMAS were performed by various organic loading rates. In order to obtain ${SBOD}_5$ removal efficiencies of more than 90%, the F/Mv ratios of PBR, FBR, MMCMAS were 0.11 kgBOD/kgMLVSS$\cdot$d, 0.12 kgBOD/kgMLVSS$\cdot$d, and 0.37 kgBOD/kgMLSS$\cdot$d, respectively. So MMCMAS system which has more active microorganisms showed better capability of organic removal and also stronger dynamic and shock loadings than those of PBR and FBR. In PBR and FBR, the media packing ratio of 20% showed better performance of organic matters removal effciencies than 10% and 30%, but sludge production rate at media packing ratio of 30% was relatively lower than that of 10% and 20%. When more than 90% organic matters removal efficiency was obtained, the ratios of attached biomass to total biomass at PBR, FBR, MMCMAS were 89~99%, 87~98%, and 54~80%, respectively. The ratio of attached biomass to total biomass was low in MMCMAS. This was formation of thin biofilm due to shear force between rotaing disc and water. The average sludge production rates(kgVSS/kgBODrem.) of PBR, FBR and MMCMAS were 0.20, 0.29 and 0.54, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2990-2996
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• 2009

S. mutans, one of a major causal agents of dental caries, is component of the dental plaque and produces various organic acids such as lactic acid as the end-product of glycolysis. In this study, we are interested in comparing the gene expression of acid-shocked and control cells of S. mutans isolated from Korean with caries. Expression levels of gtfB, gtfC, gtfD and ftf were analyzed by Real-time PCR, when the cells were grown under 20 mM lactic acid stress in the exponential phase. The data showed reduced expression of these genes. S. mutans is known to have developed a variety of mechanisms to tolerate acid sterss. A more detailed analysis of the functions and interactions of acid stress proteins connecting the growth, stress tolerance, biofilm formation is under way.

• Journal of Microbiology and Biotechnology
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• v.26 no.4
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• pp.748-756
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• 2016

In the present study, a lipopeptide (named AXLP14) antagonistic to Xanthomonas oryzae pv. oryzae (Xoo) was obtained from the culture supernatant of Bacillus amyloliquefaciens B014. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis demonstrated that AXLP14 consisted of surfactin homologs. The minimum inhibition concentration and minimum bactericidal concentration of AXLP14 against Xoo were determined to be 1.25 and 2.50 mg/ml, respectively. At a concentration of 0.613 mg/ml, AXLP14 strongly inhibited the formation of Xoo biofilm. AXLP14 also inhibited the motility of Xoo in a concentration-dependent manner. Applying AXLP14 to rice seedlings significantly reduced the incidence and severity of disease caused by Xoo. In Xoo-infected rice seedlings, AXLP14 strongly and continuously up-regulated the expression of both OsNPR1 and OsWRKY45. In addition, AXLP14 effectively inhibited the Xoo-induced up-regulation of the expression of the abscisic acid biosynthesis gene OsNECD3 and the abscisic acid signalingresponsive gene OsLip9, indicating that AXLP14 may protect rice against Xoo-induced disease by enhancing salicylic acid defense and interfering with the abscisic acid response to virulence.

• Environmental Engineering Research
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• v.13 no.1
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• pp.19-27
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• 2008

Simultaneous removal of ternary gases of $NH_3$, $H_2S$ and toluene in a contaminated air stream was investigated over 180 days in a biofilter. A commercially available inorganic/polymeric composite chip with a large void volume (bed porosity > 0.80) was used as a microbial support. Multiple microorganisms including Nitrosomonas and Nitrobactor for nitrogen removal, Thiobacillus thioparus (ATCC 23645) for $H_2S$ removal and Pseudomonas aeruginosa (ATCC 15692), Pseudomonas putida (ATCC 17484) and Pseudomonas putida (ATCC 23973) for toluene removal were used simultaneously. The empty bed residence time (EBRT) ranged from 60 - 120 seconds and the inlet feed concentration was $0.0325\;g/m^3-0.0651\;g/m^3$ for $NH_3$, $0.0636\;g/m^3-0.141\;g/m^3$ for $H_2S$, and $0.0918\;g/m^3-0.383\;g/m^3$ for toluene, respectively. The observed removal efficiency was 2% - 98% for $NH_3$, 2% - 100% for $H^2S$, and 2% - 80% for toluene, respectively. Maximum elimination capacity was about $2.7\;g/m^3$/hr for $NH_3$, > $6.4\;g/m^3$/hr for $H_2S$ and $4.0\;g/m^3$/hr for toluene, respectively. The inorganic/polymeric composite carrier required 40 - 80 days of wetting time for biofilm formation due to the hydrophobic nature of the carrier. Once the surface of the carrier was completely wetted, the microbial activity became stable. During the long-term operation, pressure drop was negligible because the void volume of the carrier was two times higher than the conventional packing materials.

• Journal of the Korean Applied Science and Technology
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• v.36 no.4
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• pp.1338-1348
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• 2019

The Geomunoreum Lava Tube System, declared as a UNESCO World Heritage Site, has a unique natural ecosystem. The information available about this ecosystem, which contains lava caves with secondary carbonate speleothems, is sparse. Hence, extensive research is warranted for establishing a conservation standard. We commenced microbial research on the system and have been studying the microorganisms coating the lava tube wall to acquire fundamental information for understanding the lava cave ecology of Jeju Island. Samples were collected from yellow-colored walls in six caves that are part of the system-the Bengdwi, Utsanjeon, Bukoreum, Manjang, Gimnyeong, and Yongcheon caves. This study focused on yellow walls as it is the most easily distinguished color. According to previous studies, the color of cave walls is attributed to microorganisms or their components. To determine whether the yellow mats from the Jeju lava tube walls are caused by microorganisms, we examined samples at the microscopic scale, by staining mats and analyzing bacterial isolates from glitter particles. As a result, we found that the yellow walls of lava tubes are comprised of microbial mats.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.642-649
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• 2007

The effectiveness of add-on tertiary treatment processes for the polishing of the effluent of a biological nutrient removal (BNR) system from a modified $A^2/O$ process has been examined under the field condition with pilot-scale plants. The add-on treatment processes of 1) combined biofilm anoxic reactor and sand filtration, and 2) two-stage denitrification filter had been operated with various operating conditions. The experimental results indicated that two-stage denitrification filter could produced a better polished tertiary effluent. Filtration rate of $150m^3/m^2{\cdot}d$ for the 2-stage denitrifying filter could decrease the nitrate removal probably due to shorter detention time that caused insufficient reaction for denitrification. Two stage denitrification filter operated with M/N ratio of 3.0 and filtration rate of $100m^3/m^2{\cdot}d$ produced the tertiary effluent with nitrate and SS concentraitons of 2.8 mg/L and 2.3 mg/L, respectively. When the operating temperature reduced $30^{\circ}C$ to $18^{\circ}C$, $NO_3{^-}-N$ removal efficiency decreased from 73% to 68%.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.5
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• pp.547-555
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• 2009

The objectives of this research were focused on the effects of various operating parameters on nitrous oxide emission such as C/N ratio, ammonia concentration and HRT in the hybrid and suspension reactors. With the decreasing of C/N ratios, $N_2O$ emission rates in the both processes were increased because organic carbon source for denitrification was depleted. In case of biofilm reactor operated using medium, $N_2O$ release from the nitrification was not affected by the variation of ammonia concentration. But in the suspension reactor, $N_2O$ production from the nitrification was rapidly increased with the increase of ammonia. Nitrite accumulation caused by undesirable nitrification conditions could be a important reason for the increase in the $N_2O$ production from the aerobic reactor. And rapid increase in $N_2O$ production was reflected by the decrease of HRT, similar to the results observed in the results of ammonia loading changes. So it could be said that it is very important to put in consideration both its optimum conditions for wastewater treatment efficiency and suitable conditions for $N_2O$ diminish, simultaneously, in order to development an eco-friendly and advanced wastewater treatment, especially in BNR process.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.2
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• pp.195-202
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• 2018

The purpose of this study is to analyze the cariogenicity of vitamin supplements for children by the Caries Potentiality Index (CPI), pH drop capacity, proliferation rate of Streptococcus mutans. Four vitamin supplements were selected - Noma (NM), Cenovis Kids (CK), Animal Parade (AP), and Character Vitamin (CV). CPI value decreased in the order of AP, CV, CK, and NM. Initial values of all experimental groups showed acidity below pH 7.0. Analysis of the colony forming units of Streptococcus mutans showed that NM and CV resulted a higher proliferation rate (p < 0.05) than CK and AP (p < 0.05). Bacterial activity of the control group was lower than other groups when observed with a confocal laser scanning microscope. Considering the bacterial activity and acidity of vitamin supplements, it is necessary to pay close attention when children taken the vitamin supplements for their oral health.