• Microbiology and Biotechnology Letters
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• v.38 no.2
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• pp.207-215
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• 2010

The purpose of this research is to draw the bacterial community difference between Korean and Chinese kimchi for future use in the confirmation of kimchi origin. Initial fermentation stage kimchi samples (above pH 5) were used for the analysis of bacterial diversity. From 26 Korean kimchi samples, 1,017 strains in the 45 genera and from 22 Chinese kimchi samples, 842 strains in the 54 genera were isolated with use of marine medium, nutrient medium, succinate minimal medium (SMM), leuconostocs selective medium (LUSM) agars. In the order of isolated numbers, Bacillus, Weissella, Leuconostoc, Pseudomonas, and Lactobacillus genera and Bacillus, Weissella, Lactobacillus, Pseudomonas, Serratia, and Enterobacter genera were predominated in Korean and Chines kimchi, respectively. Among the isolated lactic acid bacteria, Weissella spp. were isolated most dominantly owing to the biased growth of Weissella spp. on LUSM agar. Species in the genera Leuconostoc and Lactobacillus were the next frequently isolated LAB from Korean and Chinese kimchi, respectively. Weissella confusa was isolated only from Korean kimchi and W. soli and Serratia proteamculans were isolated only from Chinese kimchi. They have a possibility to be used as target bacteria to differentiate Korean kimchi from Chinese kimchi.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.906-913
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• 2004

A culture-independent molecular phylogenetic survey was carried out on the bacterial community in cold-seep sediment at Edison Seamount, south of Lihir Island, Papua New Guinea. Small-subunit rRNA genes were amplified directly from the sediment DNA by PCR and cloned. The majority of the cloned 16S rRNA gene sequences were most closely related to as-yet-uncultivated microorganisms found in deep-sea sediments, and were primarily affiliated with one of four groups: the $\gamma$-, $\delta$-, and $\epsilon$-subdivisions of Proteobacteria, and Cytophaga-Flavobacterium-Bacteroides. We did not recover any sequences related to cyanobacteria, prochlorophytes, and $\alpha$-Proteobacteria, which are known to occur in great abundance within the surface mixed layer of the Atlantic and Pacific Oceans. The majority of the cloned $\gamma$-and $\epsilon$-Proteobacterial sequences were closely related to chemoautotrophic sulfur-oxidizing symbionts of marine benthic fauna, and the $\delta$-Proteobacterial sequences to sulfate- and sulfur-reducing bacteria, indicating that they might play an important role in chemoautotrophic primary production and the sulfur cycle in the cold-seep area. There results demonstrate the high diversity of the bacterial community in the cold-seep sediment, and substantially expand knowledge of the extent of bacterial diversity in this formidable and unique habitat.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.6
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• pp.356-361
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• 2007

Recently, the development of various culture-independent identification techniques for environmental microbes has greatly enhanced our knowledge of microbial diversity. In particular, denaturing gradient gel electrophoresis (DGGE) of 16S rDNA fragments, generated using the polymerase chain reaction (PCR) is frequently used to examine the diversity of environmental bacterial populations. This method consists of direct extraction of the environmental DNA, amplification of the 200-600 bp 16S rDNA fragments with universal primers, and separation of the fragments according to their melting point on a denaturing gradient gel. In this study, we investigated the seaside microbial community in coastal areas of Busan, Korea, using culture-independent techniques. First, marine genomic DNA was extracted from seawater samples collected at Songjeong, Gwangahn, and Songdo Beaches. Then, PCR was used to amplify the bacterial 16S rDNA using universal primers, and DGGE was used to separate the amplified 500 bp 16S rDNA fragments. Finally, the tested 16S rDNA genes were further analyzed by sequencing. Based on these experiments, we found that DGGE analysis clearly showed variation among the regional groups. It can be used to monitor rapid changes in the bacterial diversity of various environments. In addition, the sequence analysis indicated the existence of many unculturable bacteria, in addition to Arcobacter, Pseudoaltermonas, and Vibrio species.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.4
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• pp.303-309
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• 1990

To provide essential information of the role of marine bacteria on the dinoflagellate blooms, distribution of marine bacterial flora and dinoflagellate species was investigated in Chinhae Bay located in southern part of Korea from August 1989 to April 1990. Two hundred and fifty one strains of marine bacteria were isolated from seawater samples collected from the study area. Among them, Flavobacterium spp. and Acinetobacter spp. were the most dominant in bacterial flora. Another 32 strains which comprised 13 percent of total strains were Erythrobacter spp.. Based on the physiological character, Erythrobacter spp. were identified as Erythrobacter longus, Erythrobacter sp.(J-2) and Erythrobacter sp. (J-8). From the phytoplanktonic community, fourteen genera and twenty nine taxa of dinoflagellate species were identified. Based on the spatio-temporal frequence and abundance Gymnodinium sanguneum, Prorocentrum micans and Prorocentrum minimum were the aestival dominent species. However, Heterocapsa triquetra was appeared as predominant species in April. Cell density of about 2,000 cells/ml was prevailed in the bloom of August, but it developed into more intensive bloom of above 500 cells/ml in September. The water quality showed eutrophic or hypereutrophic condition, which was proved by high concentration of dissolved inorganic nitrogen, ortho-phosphate and chemical oxygen demand. Oxygen deficient water mass was found in the bottom overlying waters in August and September. High relationship between abundant bacterial flora and persistent dinoflagellate blooms in eutrophic condition would be approvable.

• Microbiology and Biotechnology Letters
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• v.43 no.1
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• pp.65-78
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• 2015

The bacterial diversity of the rhizosphere soil of S. japonica native to Suncheon bay was analyzed. Ninety two strains showing different morphological characteristics were isolated from the soils around the community of S. japonica. Bacterial diversity and distributions were studied by phylogenetic analysis of the partial 16S rDNA sequences. Ninety two strains were partially sequenced and analyzed phylogenetically. These strains were composed of 5 phyla firmicutes (56.5%), gamma-proteobacteria (29.3%), alpha-proteobacteria (5.4%), actinobacteria (5.4%), bacteroidetes (3.3%) and Shannon’s diversity index (H') were different from each of sampling sites (1.675, 1.924 and 2.04). Eleven isolates were presumed to be novel species candidates based on similarity analysis of the 16s rRNA gene sequences. Overall, Firmicutes and gamma-proteobacteria of the rhizosphere soil of S. japonica showed a high diversity.

• Food Science of Animal Resources
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• v.26 no.3
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• pp.402-409
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• 2006

Although microorganisms are, in fact, the most diverse and abundant type of organism on Earth, the ecological functions of microbial populations remains poorly understood. A variety of bacteria including marine Vibrios encounter numerous ecological challenges, such as UV light, predation, competition, and seasonal variations in seawater including pH, salinity, nutrient levels, temperature and so forth. In order to survive and proliferate under variable conditions, they have to develop elaborate means of communication to meet the challenges to which they are exposed. In bacteria, a range of biological functions have recently been found to be regulated by a population density-dependent cell-cell signaling mechanism known as quorum-sensing (QS). In other words, bacterial cells sense population density by monitoring the presence of self-produced extracellular autoinducers (AI). N-acylhomoserine lactone (AHL)-dependent quorum-sensing was first discovered in two luminescent marine bacteria, Vibrio fischeri and Vibrio harveyi. The LuxI/R system of V. fischeriis the paradigm of Gram-negative quorum-sensing systems. At high population density, the accumulated signalstrigger the expression of target genes and thereby initiate a new set of biological activities. Several QS systems have been identified so far. Among them, an AHL-dependent QS system has been found to control biofilm formation in several bacterial species, including Pseudomonas aeruginosa, Aeromonas hydrophila, Burkholderia cepacia, and Serratia liquefaciens. Bacterial biofilm is a structured community of bacterial cells enclosed in a self-produced polymeric matrix that adheres to an inert or living surface. Extracellular signal molecules have been implicated in biofilm formation. Agrobacterium tumefaciens strain NT1(traR, tra::lacZ749) and Chromobacterium violaceum strain CV026 are used as biosensors to detect AHL signals. Quorum sensing in lactic acid bacteria involves peptides that are directly sensed by membrane-located histidine kinases, after which the signal is transmitted to an intracellular regulator. In the nisin autoregulation process in Lactococcus lactis, the NisK protein acts as the sensor for nisin, and NisR protein as the response regulator activatingthe transcription of target genes. For control over growth and survival in bacterial communities, various strategies need to be developed by which receptors of the signal molecules are interfered with or the synthesis and release of the molecules is controlled. However, much is still unknown about the metabolic processes involved in such signal transduction and whether or not various foods and food ingredients may affect communication between spoilage or pathogenic bacteria. In five to ten years, we will be able to discover new signal molecules, some of which may have applications in food preservation to inhibit the growth of pathogens on foods.

• Journal of Microbiology and Biotechnology
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• v.26 no.5
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• pp.883-890
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• 2016

Marine sediments are a microbial biosphere with an unknown physiology, and the sediments harbor numerous distinct phylogenetic lineages of Bacteria and Archaea that are at present uncultured. In this study, the structure of the archaeal and bacterial communities was investigated in the surface and subsurface sediments of Jeju Island using a next-generation sequencing method. The microbial communities in the surface sediments were distinct from those in the subsurface sediments; the relative abundance of sequences for Thaumarchaeota, Actinobacteria, Bacteroides, Alphaproteobacteria, and Gammaproteobacteria were higher in the surface than subsurface sediments, whereas the sequences for Euryarchaeota, Acidobacteria, Firmicutes, and Deltaproteobacteria were relatively more abundant in the subsurface than surface sediments. This study presents detailed characterization of the spatial distribution of benthic microbial communities of Jeju Island and provides fundamental information on the potential interactions mediated by microorganisms with the different biogeochemical cycles in coastal sediments.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.227-234
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• 2012

Recently, the population of toxic and/or unusable jellyfish is increasing during summer along the east coast of Korea, causing massive economical and ecological damage to fisheries, nuclear power plant and marine environment. To solve this problem, this study was carried out using jellyfish as a potential soil additive for horticulture. The jellyfish was solidified and homogenized, then mixed with a commercial bed soil. Allium tuberosum ROTH was planted to control bed soil (BS) and jellyfish powder mixed bed soil groups (Mixed bed soil, MBS), and following parameters were measured during five weeks: water content, electrical conductivity and growth of leaves. At the end of the experiment, bacterial community structures of each pot were analyzed by DGGE. The relative water adsorption of jellyfish powder was about 2.5 times greater compared to its dry weight. The water content of MBS group was significantly higher than BS group 6.5 to 14.2%, and the electric conductivity of MBS group was measured around 2.8 dS/m where BS group was resulted average of 1.8 dS/m. However, the leaves of BS group were grown 30% longer compared to MBS group. DGGE analysis of MBS group was shown in high number of phylum Bacteroidetes and increased diversity of Sphingobacteriia compared to BS group. Jellyfish powder as a soil additive surely will be a good candidate as humectant and microbiota stimulator, although there are several obstacles such as high electrical conductivity and residual alum salt which used for solidification of jellyfish.

• Korean Journal of Environmental Biology
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• v.25 no.3
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• pp.273-278
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• 2007

The cell numbers of heterotrophic bacteria inhabiting the surface and bottom sea water harvested from the 5 stations in the marine ranching ground of Tongyeong coastal waters in $2003{\sim}2007$ were examined, and species composition of the heterotrophic bacterial population and dominant species were analyzed as well. Sea water samples collected in summer season contained much higher number of heterotrophic bacteria than those harvested in winter, spring and autumn seasons due to the higher sea water temperature. However the cell number of heterotrophic bacteria did not show a significant dependence on the location of the sampling stations. The cell number of heterotrophic bacteria in the surface sea water harvested in October 2003 and in September 2004 was not discernibly different from that in the bottom sea water and sometimes the former was even fewer than the latter because of the typhoon and localized torrential downpour. The number of heterotrophic bacteria decreased every year. The main bacterial species were Pseudomonas fluorescens TY1, Pseudomonas stutzeri TY2, Acinetobacter lwoffii TY3, Sphingomonas paucimobilis TY4, Burkholderia mallei TY5, Pasteurella haemolytica TY6, Pasteurella multocida TY7, Comamonas acidovorans TY8, Actinobacillus ureae TY9 and Chryseobacterium indologenes TY10. P. fluorescens TY1 and A. lwoffii TY3 were found to be the dominant species.

• Journal of Marine Bioscience and Biotechnology
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• v.13 no.1
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• pp.10-19
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• 2021

This study investigated how ozone treatment can successfully inactivate pathogenic bacteria in both artificial seawater and effluents discharged from the fishery quarantine station in Pyeongtaek Port, Korea. Vibrio sp. and Streptococcus sp. were initially inoculated into the artificial seawater. All microbes were almost completely inactivated within 10 min and 30 min by injecting 6.4 mg/min and 2.0 mg/min of ozone, respectively. It was discovered that the water storing Pleuronichthys, Pelteobagrus, and Cyprinus imported from China contained the indicator bacteria, Vibrio sp., Enterococcus sp., total coliforms, and heterotrophic microorganisms. Compared to the control, three indicator bacteria were detected at two to six times higher concentrations. The water samples displayed a diverse microbial community, comprising the following four phyla: Bacteroidetes, Proteobacteria, Firmicutes, and Actinobacteria. Almost all indicator bacteria were inactivated in 5 min at 2.0 mg/min of ozonation; comparatively, 92.9%-98.2% of the less heterotrophic microorganisms were deactivated within the same time period. By increasing the dosage to 6.4 mg/min, 100% deactivation was achieved after 10 min. Despite the almost complete inactivation of most indicator bacteria at high doses after 10 min, several bacterial strains belonging to the Proteobacteria have still been found to be resistant under the given operational conditions.