• Biomedical Science Letters
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• v.28 no.4
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• pp.317-321
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• 2022

Due to COVID-19 pandemic, wearing face masks is obligatory to prevent respiratory virus transmissions in the community. However, there are few studies of the desirable number of wearing a face mask, and how to store them for reuse. Therefore, in this study, a survey was conducted among 208 healthy adults, and 27 kf-94 masks worn for 1, 2, and 3 days were collected. To estimate the risk of bacterial contamination, we analyzed the extent of bacterial contamination of the BHI medium and 16S rRNA gene sequencing. With an increase in the number of days of using the mask, the degree of bacterial contamination of the used mask gradually increased. As a result of 16S rRNA PCR performed for strain identification, Staphylococcus, known as a pathogenic bacterium, was identified the most. In conclusion, we found that wearing a cotton KF mask provides an optimal environment for microbes, which are related to the skin and respiratory system, to thrive. Therefore, it is also important to reduce the risk of bacterial infection of the face mask with appropriate sterilization methods.

• Journal of Oral Medicine and Pain
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• v.47 no.1
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• pp.10-26
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• 2022

Purpose: The purpose of this study was to investigate whether various saliva collection methods affect the observed salivary microbiome and whether microbiomes of stimulated and unstimulated saliva and plaque differ in richness and diversity. Methods: Seven sampling methods for unstimulated saliva, stimulated saliva, and plaque samples were applied to six orally and systemically healthy participants. Bacterial 16S ribosomal RNA genes of 10 major oral bacterial species, namely, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum, Prevotella intermedia, Prevotella nigrescens, Streptococcus mitis, Streptococcus sobrinus, and Lactobacillus casei, were analyzed by real-time polymerase chain reaction. We comprehensively examined the dependence of the amount of bacterial ribosomal DNA (rDNA), bacterial-community composition, and relative abundance of each species on sample collection methods. Results: There were significant differences in the bacterial rDNA copy number depending on the collection method in three species: F. nucleatum, P. nigrescens, and S. mitis. The species with the highest richness was S. mitis, with the range from 89.31% to 100.00%, followed by F. nucleatum, P. nigrescens, T. denticola, T. forsythia, and P. intermedia, and the sum of the proportions of the remaining five species was less than 1%. The species with the lowest observed richness was P. gingivalis (<0.1%). The Shannon diversity index was the highest in unstimulated saliva collected with a funnel (4.449). The Shannon diversity index was higher in plaque samples (3.623) than in unstimulated (3.171) and stimulated (3.129) saliva and in mouthwash saliva samples (2.061). Conclusions: The oral microbial profile of saliva samples can be affected by sample collection methods, and saliva differs from plaque in the microbiome. An easy and rapid technique for saliva collection is desirable; however, observed microbial-community composition may more accurately reflect the actual microbiome when unstimulated saliva is assayed.

• Korean Journal of Microbiology
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• v.39 no.4
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• pp.260-266
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• 2003

In this study bacterial community was analyzed to evaluate the impacts of long-term use of agricultural chemicals on a soil ecosystem as well as to obtain fundamental data on the relationship. Sequences of 16S rRNA clones from a non-agricultural site and a tangerine orchard soil which has a history of long-term use of agricultural chemicals over 30 years were analyzed. This revealed that bacterial community containing 5 divisions and 18 genera was distributed in a tangerine orchard soil, while bacterial community containing 9 divisions and 44 genera was distributed. In a tangerine orchard soil site, the most abundant bacteria in subdivision level were placed into Proteobacteria γ group which occupied 56% of total clones. The other bacterial clones from the ocrhcard soil exposed to agricultural chemicals over 30 years were Acidobacteria group (25%), Fimicutes group (5%), Planctomycetes group (2%), Proteobacteria α (1%), δ group (1%), and Cyanobacteria group (1%). Whereas, the clones were from the non-agricultural site were distributed among the division or subdivision Acidobacteria group (14%), Planctomycetes group (13%), Proteobacteria α (10%), β (9%), δ (9%), Fimicutes group (8%), Verrucomicrobia group (8%), Actinobacteria group (6%), Proteobacteria γ group (3%), Bacteroidetes group (3%), Gemmatimonadetes group (3%), and Cyanobacteria group (1%). This finding suggests the possibility that long-term application of agricultural chemicals or fertilizers on a tangerine orchard might result in drastic reduction or alteration in the composition of the bacterial community in the contaminated soil site.

• The Korean Journal of Community Living Science
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• v.25 no.4
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• pp.629-636
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• 2014

Polybrominated diphenyl ethers (PBDEs) as flame-retardant additives have been used in a wide array of products, including building materials, electronics, furnishings, motor vehicles, airplanes, plastics, polyurethane foams, and textiles. They are structurally similar to PCBs and other polyhalogenated compounds. PBDEs are found in a variety of foods, and 95% of all human exposure to POPs comes from food. The major food sources are fish/seafood and dairy products. A number of studies have reported high levels of PBDEs in animals, increasing the public's concern over PBDE levels in animals. This study evaluates the relationship between the level of PBDEs according to piglet diseases. Salmonella spp. and Streptococcus are bacterial diseases. Porcine respiratory reproductive syndrome (PRRS) is a viral disease. The concentration of PBDEs in the piglet liver from viral diseases was higher than that from bacterial diseases. BDE-47 and BDE-99 were detected in most samples. More PBDEs were detected in the piglet liver from PRRS of North American type than from that of European type.

• Korean Journal of Microbiology
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• v.27 no.3
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• pp.265-271
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• 1989

Bacteria isolated from Cheonsu Bay at 4 seasons were analyzed by numerical taxonomic method. Results of 48 morphological, physiological and biochemical tests showed different adaptability of bacteria to temperature in consequence with sampling season and isolated bacteria were able to survive at various environmental conditions, Identification results revealed that Enterobacteriaceae, Aeromonas, Pseudomonas and Vibrio were dominant genera in geterotrophic bacterial community. For each season, Aeromonas was most dominant in spring and autumn, Pseudomonas and Enterobacteriaceae in summer and winter, respectively. Cluster ananlysis was performed and all vacteria were clustered into 29 phenetic groups. Seasonal characteristics were distict in each group. Different physiological characteristics and species compositions for each season contribute to the stability and diversity of environmental ecosystem.

• Journal of Microbiology and Biotechnology
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• v.24 no.11
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• pp.1473-1483
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• 2014

Reports of herbicide resistance events are proliferating worldwide, leading to new cultivation strategies using combinations of pre-emergence and post-emergence herbicides. We analyzed the impact during a one-year cultivation cycle of several herbicide combinations on the rhizobacterial community of glyphosate-tolerant Bt-maize and compared them to those of the untreated or glyphosate-treated soils. Samples were analyzed using pyrosequencing of the V6 hypervariable region of the 16S rRNA gene. The sequences obtained were subjected to taxonomic, taxonomy-independent, and phylogeny-based diversity studies, followed by a statistical analysis using principal components analysis and hierarchical clustering with jackknife statistical validation. The resilience of the microbial communities was analyzed by comparing their relative composition at the end of the cultivation cycle. The bacterial communites from soil subjected to a combined treatment with mesotrione plus s-metolachlor followed by glyphosate were not statistically different from those treated with glyphosate or the untreated ones. The use of acetochlor plus terbuthylazine followed by glyphosate, and the use of aclonifen plus isoxaflutole followed by mesotrione clearly affected the resilience of their corresponding bacterial communities. The treatment with pethoxamid followed by glyphosate resulted in an intermediate effect. The use of glyphosate alone seems to be the less aggressive one for bacterial communities. Should a combined treatment be needed, the combination of mesotrione and s-metolachlor shows the next best final resilience. Our results show the relevance of comparative rhizobacterial community studies when novel combined herbicide treatments are deemed necessary to control weed growth.

• Journal of Microbiology and Biotechnology
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• v.13 no.2
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• pp.251-255
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• 2003

The bacterial compositions of seven hot-pepper sown soil were compared in this study. From the 624 isolates, 95 species and 49 genera were identified by fatty acid methyl ester analysis (FAME). The FAME results of seven soil showed two distinct clusters for aerobic and Gram-negative bacteria in the high productivity and monoculture soil samples. While Arthrobacter ($17\%$), Kocuria ($11\%$), Pseudomonas ($8\%$), and Bacillus ($8\%$) were predominant among bacteria which were cultured on heterotrophic (YG) agar medium, Pseudomonas ($56\%$), Stenotrophomonas ($16\%$), and Burkholderia ($8\%$) were predominant on crystal violet agar medium. Shannon Weaver indices (H) indicated that colonies obtained from heterotrophic agar medium (3.1) were found to be more diverse than those obtained from the crystal violet media (1.9). The results suggest that FAME analysis may be a potential indicator for of soil quality.

• Korean Journal of Environmental Biology
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• v.39 no.4
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• pp.515-522
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• 2021

Jeotgal is a salty and fermented traditional Korean fish sauce. Unlike most other previous studies that investigated samples purchased from retail markets, this study focused on samples of jeotgal with traceable history to Yeonggwang, a timehonored fishing village in Korea. Three jeotgal samples, which were made from small yellow croakers, largehead hairtail, and miscellaneous fish, were selected based on information obtained from interviews with local craftsmen and literature reviews. Bacterial community profiles of the three jeotgal samples were investigated to identify indicator (and potentially core) bacteria for jeotgal ripening. The 16S rRNA gene-based metagenomic analysis revealed that the dominant phyla and classes, (Gammaproteobacteria, Betaproteobacteria, Bacilli, and Clostridia) of the three different jeotgal were identical, albeit with different composition ratios. Diversification was evident beginning at the order level. Interestingly, each dominant order was mainly comprised of single members even at the genus level. The dominant genera included Halomonas, Tetragenococcus, Halanaerobium, Pseudomonas, Massilia, and Lentibacillus. This observed genus-level heterogeneity suggests that there are diverse bacterial signatures in jeotgal and that these can be used as indicators for jeotgal ripening and/or as starters to increase its sensory quality and functionality.

• Journal of Life Science
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• v.24 no.5
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• pp.522-531
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• 2014

Seasonal variations in the bacterial community of Gwangyang Bay seawater were analyzed using both isolation and cultivation-independent methods. Amplified rDNA restriction analysis was applied to 200 bacterial isolates. Bacterial isolates were composed of four phyla: Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes. Pyrosequencing was conducted, in addition to denaturing gradient gel electrophoresis (DGGE) of genomic DNA extracted directly from the water samples. The bacterial sequences obtained by pyrosequencing of 16S rRNA genes consisted of 24 phyla in the spring and summer, 39 in the fall, and 32 in the winter. The diversity index was high in the fall, whereas the dominancy index was high in the spring. In the spring, phylum Firmicutes was dominant, whereas phylum Proteobacteria dominated in the other three seasons. The second most dominant phyla were Proteobacteria in the spring, Firmicutes in the summer, and Bacteroidetes both in the fall and winter. Bacilliaceae was the most predominant family in the spring. Rhodobacteraceae and Bacilliaceae dominated in the summer, and Rhodobacteraceae dominated in the winter. Neither was dominant in the fall Twenty-seven bands purified from DGGE profiles were cloned and analyzed phylogenetically. In the spring, phylum Firmicutes dominated, followed by Proteobacteria. Proteobacteria dominated in all other seasons. Thus, two cultivation-independent methods for determination of seasonal variation patterns at the phylum level were in accordance with each other.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.6
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• pp.1100-1107
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• 2012

Bacterial endophytes may be important factors in plant growth and ecologically relevant functions in rice. Using pyrosequencing technology, we analyzed the composition of endophytic bacterial communities that colonized the roots of rice cultivated in long-term fertilized (APK) and non-fertilized (NF) paddy soils. A total of 1,900 reads were obtained from 2 samples. All sequences were classified into 177 OTUs (APK sample) or 72 OTUs (NF sample) at a 97% similarity cut-off. Twenty-two OTUs were shared between the 2 samples, and these were also the most dominant OTUs in both samples. Proteobacteria was the most dominant phylum with 90.2%, followed by Actinobacteria (7.1%) and Bacteroidetes (1.1%). Furthermore, Pseudomonas was the most abundant genus in both samples. We observed clear differences in the structure of the endophytic bacterial community structure between the 2 samples. Notably, the distributions of Alphaproteobacteria and Gammaproteobacteria were markedly different. The diversity index of the APK sample was higher than that of the NF sample. These findings showed that the endophytic bacterial community of rice roots was affected by the presence of fertilizers in the rice field soil.