• Korean Journal of Microbiology
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• v.47 no.1
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• pp.92-96
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• 2011

Rhodococcus sp. strain DK17 possesses three megaplasmids (380 kb pDK1, 330 kb pDK2, and 750 kb pDK3). The alkylbenzene-degrading genes (akbABCDEF) are present on pDK2 while the phthalate operons which are duplicated are present on both pDK2 (ophA'B'C'R') and pDK3 (ophABCR). DK17 with an optimal temperature of $30^{\circ}C$ showed no growth at $37^{\circ}C$. When transferred to $30^{\circ}C$, however, the $37^{\circ}C$ culture began to grow immediately, indicating that $37^{\circ}C$ is not lethal but stressful for DK17 growth. In addition, when exposed to $37^{\circ}C$ even for a short time, a part of DK17 cells lost the ability to degrade o-xylene (a model compound of alkylbenzenes). When two hundred colonies were randomly selected for colony PCR for pDK2-specific akbC, ophC', or pDK3-specific ophC, a total of 29 colonies were found to have lost at least one of the three genes. PFGE analysis clearly showed that all the mutants have different megaplasmid profiles from that of DK17 wild type, which are divided into five different cases: Type I (10 mutants, pDK2 loss and acquisition of a new ~700 kb plasmid), Type II (9 mutants, pDK2 loss), Type III (8 mutants, pDK3 loss and acquisition of a new ~400 kb plasmid), Type IV (1 mutant, pDK3 loss), and Type V (1 mutant, pDK2 and pDK3 loss and acquisition of the ~400 kb and ~700 kb plasmids). The above results showing that growth temperature changes can induce physical changes in bacterial genomes suggest that environmental changes in habitats including temperature fluctuations affect significantly the evolution of bacteria.

• Korean Journal of Environmental Agriculture
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• v.18 no.1
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• pp.77-82
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• 1999

Three floating islands have been constructed for water quality improvement for a polluted irrigation reservoir. Each floating island consists of 10 segments. Each segment hay an area of $16m^2$(4×4m) and is made of wood frames and floats(polystyrene foam). We planted three species of aquatic macrophytes(Typha angustifolia, Zizania latifolia, and Phragmites australis) in floating island on June, 1998. They grew very well without death. We would like to evaluate Phragmites australis is the most suitable aquatic macrophyte that could be planted in a floating island because it maintained the best balance of its root and shoot among them. During their grown period, net primary productivity of Typha angustifolia was $962gDM/m^2$, Zizania latifolia was $1,115gDM/m^2$, and Phragmites australis was $523gDM/m^2$. From these data, it would be estimated to 5.0Kg uptake of nitrogen by aquatic macrophytes and phosphorus 0.8Kg in 3 floating islands. The floating islands worked well as a habitat of fish and prawns. Many kinds of insect lived on the floating islands. The floating island has not only the function of water quality treatment but also several advantages: improvement of landscape and species diversity; low cost of maintenance; low technology; unnecessary of energy; less susceptible to variations in pollutant loading. It could be evaluated a good measure of water quality improvement for an irrigation reservoir. However, it should be intensively studied to develop more light, strong, durable and low-priced frames for efficient floating islands.

• Korean Journal of Environment and Ecology
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• v.23 no.6
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• pp.528-534
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• 2009

Styan's Grasshopper Warblers (Locustella pleskei) are vulnerable species distributed in East-Asia only. Its known breeding sites in Korea are remote islets including Hongdo Islet, Chilbal Islet, Mara Islet, and Chuja Islets, and, therefore, the breeding biology of this species is still poorly known. This study was conducted on Mara Islet (N $33^{\circ}$ 06', E $126^{\circ}$ 16') from May to September 2008 to investigate the breeding status and breeding site characteristics of the grasshopper warblers. A total of 11 breeding pairs and their nests were found on trees and shrubs at artificially planted forests and hedges of Pinus thunbergii. The grasshopper warblers preferentially utilized the shrub trees for nesting places, and major nesting trees were Camellia japonica, Pittosporum tobira and Pinus thunbergii as nesting trees. Average heights of nesting trees and nests were $2.77{\pm}1.10m$ and $1.75{\pm}0.56m$, respectively. The grasshopper warblers selected lower shrubs and trees for nesting than randomly selected ones around them, probably to avoid strong and prevailed winds in flat and un vegetated environments on Mara Islet. The shape of nests was a round bowl-type, and measurements of nests were $11.9{\pm}0.5cm$ in exterior nest diameter, $11.1{\pm}1.1cm$ in height of exterior nest, $5.8{\pm}0.4cm$ in interior nest depth, and 6.0cm in interior nest diameter. It incubated eggs until the early August on Mara islet, and incubation periods of Mara Islet was possibly later than that of other areas. Furthermore, the clutch size in the study area was three, and they laid smaller number of eggs than normal clutch size (4~5 eggs) reported in other areas. Although we could not observe any nest predator on this species in the study area, selective cutting and pruning of trees will diminish dense shrub layer of forests. Therefore, it may affect the breeding of this threatened species which prefers dense shrubs of artificially planted forest of Pinus thunbergii. This study suggests that detailed and consistent further research on breeding biology and habitats of the grasshopper warblers are needed to conserve and manage of Pinus thunbergii forests on Mara Islet as an important breeding site of Styan's Grasshopper Warblers.

• Korean Journal of Soil Science and Fertilizer
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• v.25 no.4
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• pp.370-377
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• 1992

A series of field and laboratory experimentes were conducted to find out the effects of kinds of crops residues and the different amount of fertilizer to the microbial interaction, chemical properties, plant growth and their interaction under continous cultivation of hot pepper, soybean, sesame and upland rice. The results obtained were summerized follows : 1. Total number of bacteria and actinomycetes were enhanced by cultivation of upland rice and soybean while no appreciable effects were obtained by the cultivation of hot pepper and sesame. 2. The number of bacteria, actinomycetes and fungi were increased by return of crop residues when the cultivation of hot pepper, soybean, sesame and upland rice. Specially, actinomycetes was remarkably increased by upland rice cultivation. 3. Increased amount of fertilizer were remarkably affected to decrease of number of soil microorganisms. Specially, actinomycetes succession was appearently affects while plant growing time. 4. The number of identified soil bacterial species were obtained high in order of Bacillus sp.>Rhizobium sp.>Agrobacterium sp.>Pseudomonas sp. The number of Gram positive bacteria were superior than that of Gram negative bateria. 5. Interaction between microbial succession and crops cultivation, the number of Bacillus sp. was increased in hot pepper, Rhizobium sp. was in soybean, and sesame, and Agrobacterium sp. were increased in soybean, respectively. 6. Survival and habitate of soil microorganisms were differ with kinds of crop, application of residue and fertilizers. Most high number of Bacillus sp. Rhizobium sp. and Pseudomonas sp. were obtained on the rhizoplane and rhizosphere while Agrobacterium sp. and Fusarium sp. were high in rhizosphere. 7. Factors in relation to change of soil microbial population was obtained high in order of climates>crops>organic>matter>fertilizer.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.8 no.1
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• pp.20-30
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• 1975

It is matter of fact processing technology must affects the quality and yield of final product and these also depend on the selection of raw material directly or indirectly. So that the estimation of tile preprocessing condition of shellfish is of great importance for distributors and processors. This study was attempted to establish the basic data for evaluating the processing suitability of baby clam, which is one of the five important shellfishes for domestic use and export. The important results are as follows: 1. The ratio of meat volume and meat weight to the holding capacity by shells may be useful for measuring the condition index of baby clams. 2. Baby clams grown in the beds with the composition of a large quantity of gravel were low in condition index value than in sand and mud. 3. If the green feed phenomenon was the prime consideration for canned baby clams, tile most suitable harvest season if October. In this period, the digestive tract in body was almost colorless. 4. As a whole, seasonal changes of moisture and fat content in baby clams were reversely correlated. Protein content increased from April and slightly decreased for a while from July to August and increased again from September. In March, the content of glycogen was 6.3 to 6.8 percent. From this period to October, glycogen was rapidly decreased. In October, it was only 0.1 to 0.2 percent but increased from November. There were little seasonal changes in pH value and crude ash content. The pH value of meat was 6.0 to 6.2 and crude ash content was about 2 percent. 5. By the results of condition index and chemical composition of baby clams, the suitable harvest season as raw materials for processing was from March to June and from September to October. 6. The steamed baby clam meat was packed with 2 percent salt solution containing 0.15 percent, citric acid or 0.5 percent $Na_2$ EDTA in a round sanitary tin can coated with C-enamel that is 203.9 ml by volume and sterilized for 60 minutes at $112^{\circ}C$. The canned product has shown a good result to reserve the natural characteristics of baby clam through six month storage at room temperature.

• Korean journal of applied entomology
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• v.55 no.1
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• pp.17-26
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• 2016

Climate change has been regarded as one of main factors to change Korean insect pest fauna. Especially, a global warming model predicts to expand habitat for insect pests originated from tropical or subtropical regions. Two insect pests, the beet armyworm (Spodoptera exigua) and the diamondback moth (Plutella xylostella), are known to overwinter in some greenhouse conditions without diapause induction in Korea. There was a clear difference between these two insects in seasonal occurrence. P. xylostella occurred only at early spring and fall seasons, but did not occur during summer. In contrast, S. exigua maintained their occurrence from late spring to fall seasons. This study set up a hypothesis that the difference in the seasonal occurrence may be resulted from variation in susceptibility to high temperature. To test the hypothesis, heat tolerance was compared between these two insects. Exposure to $42^{\circ}C$ for 40 min killed 100% individuals of P. xylostella larvae. However, most larvae of S. exigua survived in response to $42^{\circ}C$ even for 80 min. Heat tolerance varied among developmental stages in both insects. Highest tolerant stages were $4^{th}$ instar larvae and adults for P. xylostella, but $1^{st}$ instar larvae for S. exigua. Pre-exposure to $37^{\circ}C$ for 30 min significantly increased heat tolerance in both insects. Induction of heat tolerance accompanied with significant increase of glycerol contents in the hemolymph in both insects and up-regulation of three heat shock protein expressions in S. exigua. These results suggest that the differential susceptibility to high temperature explains the disappearance of P. xylostella during summer, at which S. exigua maintains its occurrence.

• Korean Journal of Ecology and Environment
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• v.53 no.3
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• pp.241-254
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• 2020

Three introduced fish species, Japanese white crucian carp (Carassius cuvieri Temminck and Schlegel, 1846), bass (Micropterus salmoides Lacepède, 1802) and bluegill (Lepomis macrochirus Rafinesque, 1819), are dominant fishes in Korean freshwater ecosystem. In this study, we analyzed habitat environment conditions of these three species and their impacts to fish communities in streams across South Korea. Fish community data were obtained from the database of the Stream/River Ecosystem Survey and Health Assessment program maintained by the Ministry of Environment and the National Institute of Environmental Research, Korea. Our results showed that species richness and Shannon diversity of fish were higher at the presence sites of introduced fish than at the absence sites. However, when the abundance of these introduced fish species was increased, the species richness and abundance of fish were decreased. An association analysis showed that the introduced fish species had a low similarity in their appearance with some indigenous fishes such as Siniperca scherzeri and Channa argus and some endemic fishes of Korea such as Zacco koreanus, Sarcocheilichthys variegatus wakiyae, and Acheilognathus yamatsutae. In addition, the introduced fish species had a low appearance similarity with a large number of fishes in their association networks. Finally, our results presented that these introduced fish species influenced the negative impacts to the stream fish communities, and they were potential risk factors for fish community in Korean freshwater ecosystem. Therefore, it is necessary that continuous monitoring and establishment of management strategy for introduced fish species to preserve fish resource and biodiversity in the Korean streams.

• Journal of Oral Medicine and Pain
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• v.35 no.2
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• pp.101-110
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• 2010

Helicobacter pylori(H. pylori) is bacterial infection, with more than half of the world population infected and oral cavity is considered second reservoir of H. pylori infection. The purpose of this study was to evaluate role of oral cavity in H. pylori infection by comparison of the mode H. pylori infection in oral cavity and stomach. We recruited 100 subjects without systemic disease including gastrointestinal disease. Samples in oral cavity taken on gingival sulcus fluid(GSF) of lower left central incisor and 1st molar, area of buccal mucosa, dorsum of the tongue, palatal and saliva. We analyzed by Nested polymerase chain reaction(PCR) for oral infection and Urea Breath Test(UBT) for gastric infection. The results were as follows : 1. Among these 100 subjects, 36(36%) were positive by Nested PCR and 33(33%) were positive by UBT(p>0.05). 2. In detection rate of H. pylori in sites taken sample, 11(11%), 8(8%), 9(9%), 3(3%), 9(9%), 7(7%) were positive on GSF of lower left central incisor and 1st molar, area of buccal mucosa, dorsum of the tongue, palatal and saliva, respectively. Statical significance was observed in samples of GSF of lower left central incisor and area of dorsum of the tongue(p<0.05). 3. In comparison of the mode of H. pylori infection in oral cavity and stomach by analytic method, positive in oral cavity and stomach was 10(10%), negative in oral cavity and positive in stomach was 23(23%), positive in oral cavity and negative in stomach was 26(26%) and negative in oral cavity and stomach was 41(41%)(p>0.05). Conclusively, we can guess that oral H. pylori is not associated with gastric H. pylori infection and normal flora.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.1
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• pp.59-69
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• 2000

Environmental factors and phytoplankton community have been bimonthly investigated in order to clarify the bioecological characteristics of coral habitats around Moonsom at the southern Cheju Island from September 1995 to July 1996. Annual mean temperature and annual mean salinity were $17.4^{\circ}C$ and 34.06 psu, respectively, showing lower temperature-higher salinity in winter and higher temperature-lower salinity in summer, which means such conditions are inadequate for coral reef formation. Nutrient concentrations represent that total nitrogen ranged from $0.07{\sim}10.08\;{\mu}M$, phosphate from $0.05{\sim}1.70\;{\mu}M$, and silicate from $3.08{\sim}21.86\;{\mu}M$. The N/P ratio showed the range of 9.59-10.60 with decreasing offshore-ward, which means the phytoplankton community could be limited by nitrogen sources. Annual mean euphotic depth was 32.0m (18.9m-48.6m) with difference according to season and reveals the close relationship with the depth of coral distribution. Chlorophyll a concentrations of phytoplankton ranged from $0.12{\sim}1.51\;{\mu}g\;L^{-1}$ and standing crops from $1.5{\times}10^3{\sim}7.0{\times}10^5\;cells\;L^{-1}$, showing higher at inshore than at offshore with a blooming in May. A total of 128 species of phytoplankton occurred in all stations, representing 99 spp. of diatoms, 26 spp. of dinoflagellates, 2 spp. of silicoflagellates and 1 sp. of blue-green algae. Diatoms are main taxa in all seasons except for occupying by dinoflagellates in summer. Among dominant species, fParalia sulcata (Ehrenberg) Cleve and Cylindrotheca closterium (Ehrenberg) Lewin & Reimann were predominant and are likely to be main food sources for coral community. Annual mean species diversity index (H') was 1.84, showing lower than around the coast line of Cheju Island.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.196-206
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• 2005

The fish community in the mid-upper region of Gam Stream was examined seasonally from 2001 to 2003 in order to perform an environmental impact assessment prior to a construction of Gamcheon Multipurpose Dam. Additional investigation was conducted in August 2004 to confirm the fish fauna reported and to examine the ecological characteristics of Zacco temminckii population. The total number of fish caught from the study sites was 1,081 fish representing 5 families 14 species. There were 6 Korean endemic species including Coreoleuciscus splendidus, Squalidus gracilis majimae, Microphysogobio yaluensis, Liobagrus mediadiposalis, Coreoperca herzi and Odontobutis platycephala, but no endangered or vulnerable species were found. Length-weight relation, condition factor (K) and relative condition factor (Kn) of Zacco temminckii were compared by the study sites and stream. The equations based on length-weight relation in Buhang and Gam Streams were TW\;=\;0.000004TL^{3.2357}$ and TW\;=\;0.000002TL^{3.3566}$, respectively indicating the fish in Gam Stream became more rotund as length increases. The condition factor (K) and relative condition factor (Kn) against total length of Zacco temminckii at two streams indicated that the fish (>70 mm) in Cam Stream (mean K and Kn= 1.116, 1.21 respectively) had better nutritional condition than those in Buhang Stream (mean K and Ln = 1.046, 1.14 respectively). The results were corresponded with natural disturbances such as drought and intensive rainfall from 2001 to 2003 followed by human activities such as stream repair works. Therefore, it is considered to perform environmental impact assessment with not only confirmation of fish composition but also examination of ecological characteristics in population- level.