• 한국수소및신에너지학회논문집
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• 제30권3호
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• pp.269-275
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• 2019

This study was conducted to evaluate the microbial communities in coupled system of a microbial electrolysis cell and an anaerobic digestion. Glucose, butyric acid, propionic acid and acetic acid were used as substrates. The maximum methane production and methane production rate of propionic acid respectively were $327.9{\pm}6.7mL\;CH_4/g\;COD$ and $28.3{\pm}3.1mL\;CH_4/g\;COD{\cdot}d$, which were higher than others. Microbial communities' analyses indicated that acetoclastic methangens were predominant in all systems. But the proportion of hydrogenotrophic methanogens was higher in the system using propionic acid as a substrate when compared to others. In coupled system of a microbial electrolysis cell and anaerobic digestion, the methane production was higher as the distribution of hydrogen, which was generated by substrate degradation, and proportion of hydrogenotrophic methanogens was higher.

• 환경생물
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• 제41권3호
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• pp.308-324
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• 2023

This study investigated unrecorded freshwater bacterial species in Korea. Water and sediment samples were collected from the Nakdong River basin from 2020-2022. Bacterial isolates obtained through the conventional culture method with commercial media were subjected to 16S rRNA gene sequencing to identify unrecorded bacterial species. Results of 16S rRNA gene sequencing of the bacterial isolates revealed that a total of 44 bacterial isolates shared 16S rRNA gene sequence similarities of more than 98.65%, with validly published bacterial species not reported in Korea yet. These isolates were phylogenetically assigned to 4 phyla, 7 classes, 21 orders, 33 families, and 42 genera. A total of 2, 6, 12, and 24 species belonged to phyla Bacillota, Bacteroidota, Actinomycetota, and Pseudomonadota, respectively. Here, we provide details of these 44 unrecorded bacterial species, including Gram staining, colony and cellular morphologies, biochemical properties, and phylogenetic position.

• Journal of Ecology and Environment
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• 제36권4호
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• pp.223-233
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• 2013

Acid deposition is one of the most serious environmental problems in ecosystems. The present study surveyed the effects of simulated acid rain on leaf litter mass loss and microbial community in the decomposing leaf litter of Sorbus anifolia in a microcosm at $23^{\circ}C$ and 40% humidity. Microbial biomass was measured by substrate-induced respiration (SIR) and phospholipid fatty acids (PLFAs), and the microbial community structures were determined by composition of PLFAs at each interval of decomposition in litter sample and at each pH treatment. The microbial biomass showed peaks at mid-stage of decomposition, decreasing at the late stage. The leaf litter mass loss of S. anifolia decreased with decreasing pH during early and mid-decomposition stages; however the mass loss becomes similar between pH treatments at late-decomposition stage. The acidification remarkably lowers the microbial biomass of bacteria and fungi; however, microbial diversity was unchanged between pH treatments at each stage of litter decomposition. With changes of decomposition stage and pH treatment there were considerable differences in replacement and compensation of microbial species. Fungi/bacteria ratio was considerably changed by pH treatment. The PLFA profile showed significantly larger fungi/bacteria ratio at pH 5 than pH 3 at the early stage of decomposition, and the difference becomes smaller at the later decomposition stage. At low pH, pH 3 and pH 4, the fungi/bacteria ratios were stable according to the litter decomposition stages. Simulated acid rain caused decreases of 10Me17:0, 16:1${\omega}$7c, 18:1${\omega}$7, 15:0, but increase of 24:0. In addition, litter mass loss showed significant positive correlation with microbial biomass measured by SIR and PLFA on the decomposing leaf litter.

• Asian-Australasian Journal of Animal Sciences
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• 제30권2호
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• pp.181-186
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• 2017

Objective: Leucaena leucocephala (Leucaena) is a perennial tropical legume that can be directly grazed or harvested and offered to ruminants as hay, silage, or fresh. However, Leucaena contain phenolic compounds, which are considered anti-nutritional factors as these may reduce intake, digestibility and thus animal performance. Therefore, the objective of this experiment was to determine effects of Leucaena silage (LS) feeding levels on rumen microbial populations, N-balance and microbial protein synthesis in dairy steers. Methods: Four, rumen fistulated dairy steers with initial weight of $167{\pm}12kg$ were randomly assigned to receive dietary treatments according to a $4{\times}4$ Latin square design. Treatments were as followings: T1 = untreated rice straw (RS; Control), T2 = 70% RS+30% LS, T3 = 40% RS+60% LS, and T4 = 100% LS. Dairy steers were fed rice straw and LS ad libitum and supplemented with concentrate at 0.2% of body weight/d. Results: Results revealed that the rumen microbial population, especially cellulolytic, proteolytic bacteria and fungal zoospores were enhanced in steers that received 60% of LS (p<0.05), whereas the amylolytic bacteria population was not affected by treatments (p>0.05). Protozoal population was linearly decreased with increasing level of LS (p<0.05). Moreover, N-balance and microbial protein synthesis were enhanced by LS feeding (p<0.05) and were the highest in 60% LS group. Conclusion: Based on this study, it could be concluded that replacement of RS with 60% LS significantly improved microbial population and microbial protein synthesis in diary steers.

• 대한수의학회지
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• 제57권3호
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• pp.159-167
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• 2017

The microbial community is known to have a key role during the rearing period of broilers. In this study, gut microbial composition and diversity were examined to evaluate the relationships between these factors and broiler growth performance. By applying 454-pyrosequencing of the V1-V3 regions of bacterial 16S rRNA genes, six fecal samples from four- and 28-day-old chickens from three broiler farms and 24 intestinal samples of broilers with heavy and light body weights were analyzed. Microbial composition assessment revealed Firmicutes to be the most prevalent phylum at farm A, while Proteobacteria were predominant at farms B and C. Fecal microbial richness and diversity indices gradually increased from four to 28 days at all three farms. Microbial diversity assessment revealed that small intestine microbial diversity was lower in heavy birds than in light birds. In light birds, the Firmicutes proportion was lower than that in heavy birds. In conclusion, each broiler farm revealed a specific microbial profile which varied with the age of the birds. The microbial communities appeared to affect growth performance; therefore, gut microbial profiles can be utilized to monitor growth performance at broiler farms.

• 한국유기농업학회지
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• 제8권3호
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• pp.91-98
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• 2000

몇가지 토양미생물제 처리가 근대의 수량과 식물체 및 토양의 화학성분, 그리고 미생물상에 미치는 영향을 조사하였다. 모든 미생물제 처리구에서 무처리에 비하여 수량이 증가하는 경향이 있었고, 특히 BLCS cattle dropping 처리구가 가장 높았다. 식물체의 화학성분에서는 모든 철구에서 Mg의 함량이 증가된 것을 제외하고 다른 성분들은 처리간에 차이가 없었고, 토양의 화학성분에서는 Tomi 처리구에서 K와 Mg의 함량이 높았으나, 다른 처리구에서는 차이가 없었다. 토양의 미생물상을 조사한 결과, 총세균수에서는 Tomi 처리구가 가장 높았고 Husk+Palma 처리구가 가장 높았고 Husk+Palma와 Tomi 처리구에서도 몹시 증가되었다. Actinomycetes와 fungi에서도 Tomi 처리구가 매우 증가하였으나, 다른 처리구간에는 차이가 없었고, pseudomonas에서도 각 처리간에 차이가 없었다.

• Bulletin of the Korean Chemical Society
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• 제25권6호
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• pp.813-818
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• 2004

A systematic study of microbial fuel cells comprised of thermophilic Bacillus licheniformis and Bacillus thermoglucosidasius has been carried out under various operating conditions. Substantial amount of electricity was generated when a redox mediator was used. Being affected by operation temperature, the maximum efficiency was obtained at 50$^{\circ}C$ with an open circuit voltage of ca. 0.7 V. While a small change around the optimum temperature did not make much effect on the cell performance, the rapid decrease in performance was observed above 70$^{\circ}C$. It was noticeable that fuel cell efficiency and discharge pattern strongly depended on the kind of carbon sources used in the initial culture medium. In the case of B. thermoglucosidasius, glucose alone was utilized constitutively as a substrate in the microbial fuel cell irrespective of used carbons sources. When B. licheniformis was cultivated with lactose as a carbon source, best charging characteristics were recorded. Trehalose, in particular, showed 41.2% coulombic efficiency when B. thermoglucosidasius was cultured in a starch-containing medium. Relatively good repetitive operation was possible with B. thermoglucosidasius cells up to 12 cycles using glucose as a carbon source, when they were cultured with lactose as an initial carbon source. This study demonstrates that highly efficient thermophilic microbial fuel cells can be constructed by a pertinent modulation of the operating conditions and by carefully selecting carbon sources used in the initial culture medium.

• 한국토양비료학회지
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• 제38권5호
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• pp.281-286
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• 2005

굴패각으로부터 제조된 굴패화석 비료 시용이 토양의 미시환경에 미치는 영향을 조사하기 위해 토양 내 microbial biomass 함량과 주요 토양효소의 활성을 조사하여 다음과 같은 결과를 얻었다. 굴패화석 시용량이 증가함에 따라 토양 내 microbial biomass C, N, P 함량이 크게 증가하였으며, 양분의 가급화와 관련 있는 주요 토양효소의 활성이 크게 증진되었다. 본 연구조건에서 굴패화석 시용에 따른 산성토양의 pH 개선은 microbial biomass P 함량 증진과 urease, ${\beta}$-glucosidase, alkaline phosphomonesterase의 활성증진에 직접적으로 영향을 주었으며, microbial biomass P와 phosphomonoesterase 활성증진은 유효인산 함량증진에 직접적으로 영향을 준 것으로 조사되었다. 결론적으로 약산성의 공시토양에 알카리성 제재인 굴패화석 시용은 토양생물과 효소 활성을 증대함으로써 작물생육에 필요한 양분공급 및 가용율 향상시키는 효과가 있는 것으로 평가되었다.

• 한국유기농업학회지
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• 제7권2호
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• pp.107-114
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• 1999

몇가지 土壤微生物劑의 處理가 배추의 收量과 土壤 및 植物體의 化學成分, 그리고 微生物相에 미치는 影響을 調査하였다. 모든 微生物劑 處理區에서 無處理에 비하여 收量이 增加하였고, 糖度 또한 增加하여 微生物劑의 處理가 배추의 收量뿐만 아니라 品質의 向上에도 매우 效果的이라고 思料되었다. 植物體의 化學成分을 調査한 結果, MPK+Compost 處理區에서 Fe와 Zn 含量이 매우 높았으나 有意性은 없었고, 다른 成分들은 處理區間에서 差異가 없었다. 土壤의 化學成分에서는 Tomi 處理區에서 K와 Mg의 含量이 높았으나, 다른 處理區에서는 差異가 없었다. 土壤의 微生物相을 調査한 結果, 總細菌數에서는 Tomi 處理區가 가장 높았고 Husk+Palma 및 MPK+Husk+Palma 處理區에서도 높게 나타났다. Bacillus는 MPK+Husk+Palma 處理區가 가장 높았고 Husk+Palma와 Tomi 處理區에서도 몹시 增加되었다. Actinomycetes와 fungi에서도 Tomi 處理區가 매우 增加하였으나, 다른 處理區間에는 差異가 없었고, psedomonas에서도 各 處理間에 差異가 없었다.

• Journal of Microbiology and Biotechnology
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• 제31권7호
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• pp.912-920
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• 2021

SOS response is a conserved response to DNA damage in prokaryotes and is negatively regulated by LexA protein, which recognizes specifically an "SOS-box" motif present in the promoter region of SOS genes. Myxococcus xanthus DK1622 possesses a lexA gene, and while the deletion of lexA had no significant effect on either bacterial morphology, UV-C resistance, or sporulation, it did delay growth. UV-C radiation resulted in 651 upregulated genes in M. xanthus, including the typical SOS genes lexA, recA, uvrA, recN and so on, mostly enriched in the pathways of DNA replication and repair, secondary metabolism, and signal transduction. The UV-irradiated lexA mutant also showed the induced expression of SOS genes and these SOS genes enriched into a similar pathway profile to that of wild-type strain. Without irradiation treatment, the absence of LexA enhanced the expression of 122 genes that were not enriched in any pathway. Further analysis of the promoter sequence revealed that in the 122 genes, only the promoters of recA2, lexA and an operon composed of three genes (pafB, pafC and cyaA) had SOS box sequence to which the LexA protein is bound directly. These results update our current understanding of SOS response in M. xanthus and show that UV induces more genes involved in secondary metabolism and signal transduction in addition to DNA replication and repair; and while the canonical LexA-dependent regulation on SOS response has shrunk, only 5 SOS genes are directly repressed by LexA.