• Journal of the korean society of oceanography
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• 제37권1호
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• pp.35-44
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• 2002

To assess the relative contribution of bacterial and phytoplankton biomasses to particulate organic matter (POM) in the water column, microbial abundance and biomass were from two transects in the western channel of the Korea Strait in 1996. Bacterial abundance had a mean value of $5.9{\times}10^5$ cells/ml and chlorophyll-a averaged 0.14 ${\mu}g/l$. Bacterial abundance in the Korea Strait showed a positive relationship with chlorophyll-a concentration, while the distribution of POM did not covary with chlorophyll-a. Particulate organic carbon (POC) and nitrogen (PON) concentrations were greater in August than in October. Bacterial carbon (POC) and nitrogen (PON) concentrations were greater in August than in October. Bacterial carbon and nitrogen biomasses were 7.29 ${\mu}gC/l$ and 1.24 ${\mu}gN/l$, respectively, during the study periods. Bacterial biomass was larger in October than in August due to the autumn phytoplankton bloom. Phytoplankton biomass based on chlorophyll-a was 7.67 ${\mu}gC/l$ for carbon and 1.10${\mu}gN/l$l for nitrogen. The ratio of bacterial carbon (BC) to phytoplankton carbon (Cp) averaged 0.95 in the Korea Strait in 1996. Bacteria may play a more significant role in the dynamics of POM than phytoplankton do in August, with BC/Cp ratio of 1.26. The ratio of BC to Cp increased with a decrease in chlorophyll-a concentration. Averaged over all the samples in both cruises, the contribution of microbial biomass to POC and PON was about 43% and 51%, respectively. Bacterial assemblage constituted a significant fraction of POC (21%) and PON (27%). Phytoplankton accounted for 22% of POC and 24% of PON. Microbial biomass played a more important role in the dynamics of POC and PON in October than in August due to a significant increase in microbial biomass in the southern transect (transect-B) in October by the autumn phytoplankton bloom. This study showed that marine microbes may constitute a significant part in the reservoir of POM in the Korea Strait.

• The Plant Pathology Journal
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• 제34권4호
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• pp.286-296
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• 2018

Maintenance of a beneficial microbial community, especially in the rhizosphere, is indispensable for plant growth and agricultural sustainability. In this sense, plant growth-promoting rhizobacteria (PGPR) have been extensively studied for their role in plant growth promotion and disease resistance. However, the impact of introducing PGPR strains into rhizosphere microbial communities is still underexplored. We previously found that the Proteus vulgaris JBLS202 strain (JBLS202) promoted growth of Kimchi cabbage and altered the relative abundance of total bacteria and Pseudomonas spp. in the treated rhizosphere. To extend these findings, we used pyrosequencing to analyze the changes in bacterial communities in the rhizosphere of Kimchi cabbage after introduction of JBLS202. The alterations were also evaluated by taxon-specific realtime PCR (qPCR). The pyrosequencing data revealed an increase in total bacteria abundance, including specific groups such as Proteobacteria, Acidobacteria, and Actinobacteria, in the treated rhizosphere. Time-course qPCR analysis confirmed the increase in the abundance of Acidobacteria, Actinobacteria, Alphaproteobacteria, and Betaproteobacteria. Furthermore, genes involved in nitrogen cycling were upregulated by JBLS202 treatment indicating changes in ecological function of the rhizosphere soil. Overall, these results indicate that introduction of JBLS202 alters both the composition and function of the rhizosphere bacterial community, which can have direct and indirect effects on plant growth. Therefore, we propose that long-term changes in bacterial composition and community-level function need to be considered for practical use of PGPRs.

• Journal of Forest and Environmental Science
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• 제32권3호
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• pp.237-252
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• 2016

Improved knowledge of the environmental factors affecting the natural regeneration of tree species in limestone forest is urgently required for species conservation. We examined the environmental factors and tree species characteristics that are important for colonization in diverse forest stands growing on a limestone hill in northern Thailand. Our analysis estimated the relative influence of forest structure and environmental factors on the regeneration traits of tree species. We established sixty-four $100-m^2$ plots in four forest stands on the limestone hill. We determined the species composition of canopy trees, regenerating seedlings, and saplings in relation to the physical environment. The relationships between environmental variables and tree species abundance were assessed by canonical correspondence analysis (CCA), and we used generalized linear mixed models to examine data on seedling/sapling abundances. The CCA ordination indicated that the abundance of tree species within the mixed deciduous forest was closely related to soil depth. The abundances of tree species growing within the sink-hole and hill-slope stands were positively related to the extent of rocky outcropping; light and soil moisture positively influenced the abundance of tree species in the hill-cliff stand. Physical factors had a greater effect on tree regeneration than did factors related to forest structure. Tree species, such as Ficus macleilandii, Dracaena cochinchinensis, and Phyllanthus mirabilis within the hill-cliff or sink-hole stand, colonized well on large rocky outcroppings that were well illuminated and had soft soils. These species regenerated well under conditions prevailing on the limestone hill. The colonization of several species in other stands was negatively influenced by environmental conditions at these sites. We found that natural regeneration of tree species on the limestone hill was difficult because of the prevailing combination of physical and biological factors. The influence of these factors was species dependent, and the magnitude of effects varied across forest stands.

• 천문학회지
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• 제56권1호
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• pp.11-22
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• 2023

We report the result of a high-resolution spectroscopic study on seven magnesium (Mg) enhanced stars. The high Mg abundances in these stars imply that they were born in an environment heavily affected by the nucleosynthesis products of massive stars. We measure abundances of 16 elements including Mg and they show various abundance patterns implying their diverse origin. Three of our program stars show a very high Mg to Si ratio ([Mg/Si] ≈ 0.18-0.25), which might be well explained by fall-back supernovae or by supernovae with rapid rotating progenitors having an initial mass higher than about 20 M_⊙. Another three of our program stars have high light to heavy s-process element ratios ([Y/Ba] ≈ 0.30-0.44), which are consistent with the theoretical prediction of the nucleosynthesis in rapidly rotating massive stars with an initial mass of about M = 40 M_⊙. We also report a star having both high Y ([Y/Fe] = 0.2) and Ba ([Ba/Fe] = 0.28) abundance ratios, and it also shows the highest Zn abundance ratio ([Zn/Fe] = 0.27) among our sample, implying the nucleosynthesis by asymmetric supernova explosion induced by very rapid rotation of a massive progenitor having an initial mass between 20 M_⊙ ≲ M ≲ 40 M_⊙. A relative deficiency of odd-number elements, which would be a signature of the pair-instability nucleosynthesis, is not found in our sample.

• 한국해양학회지:바다
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• 제3권4호
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• pp.249-260
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• 1998

해수에 잠긴 인공기질 표면에서 미세조류의 부착과 후속적으로 나타나는 성장과정을 이해하기 위해 규조류의 부착과 주변수의 종 급원(species pool)과의 관계를 조사하였다. 1995년 7월부터 1997년 2월까지 인천항 내에서 아크릴 슬라이드를 이용하여 규조류의 부착에 관해 연구하였고, 주변 해수를 조사하였다. 또한 생물막 초기형성 과정에서 노출시간의 증가에 따라 나타나는 부착미세조류 군집의 종조성과 수도의 변화를 유리, 아크릴, 티타늄, 구리 및 생물오손방지 페인트로 도포된 슬라이드 등 다양한 인공기질 표면을 이용하여 조사하였다. 아크릴 슬라이드에서 규조류의 이입률은 주변수의 저서규조류의 수도변화와 유의성 있는 상관관계를 나타냈으며 ($r^2$=0.78, p<0.01, n=42), 이는 주변수의 저서규조류의 수도에 의해 영향을 받는 것을 지시한다. 아크릴 슬라이드에서 봄철에 단배선 형태 규조류의 부착능력(이입계수)이 복배선 형태에 비해 5 배 높게 나타났다. 그러나 부착점유율은 단배선 형태가 복배선 형태에 비해 3 배 낮게 나타났다. 겨울철에는 중심형 규조류의 부착능력이 다른 형태들에 비해 높게 나타났고 부착점유율도 높게 나타났다. 이는 규조류의 부착이 주변해수에 출현한 저서 규조류의 수도 및 부착능력에 의한 결과임을 지시한다. 우상형 규조류가 연구기간동안 모든 인공기질 표면에 대부분 부착 출현하였고, 겨울철에는 중심형 규조류가 모든 인공기질 표면에 우정 부착하였다. 생물오손방지 페인트로 처리된 표면에서는 독성에 대한 내성이 강한 것으로 판단되는 Hantzschia virgata, Licmophora abbreviata, Melosira nummuloides가 우점하여 부착하였다. 노출시간이 증가함에 따라 부착규조류의 수도는 유리, 티타늄, 아크릴 슬라이드에서 지수적으로 증가하였고, 최대수도는 유리 ${\geq}$ 아크릴 > 티타늄 > 구리 ${\geq}$ 페인트처리 슬라이드의 순으로 높게 나타났다. 모든 인공기질 표면에서 부착규조류의 성장률은 $2{\sim}3^{\circ}C$에서 보다 $24{\sim}25^{\circ}C$의 수온에서 높게 나타났고, 유리 슬라이드에서 다른 표면에 비해 전반적으로 높은 값을 보였다. 해수 중에서 노출시간의 증가에 따라 관찰된 우점종은 납작한 형태인 Amphora coffeaeformis, 부채꼴 형태인 Synedra tabulata, stalk 형태인 Licmophora paradoxa 그리고 사슬형태인 M. nummuloides로 나타났고, 부착미세조류 군집에서 미소천이(micro-succession)가 관찰되었다. 이러한 우점종 조성은 미세조류 생물막이 발달하여 서식공간이 제한됨에 따라 나타난 종 적응의 결과로 보인다.

• 환경생물
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• 제18권2호
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• pp.215-226
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• 2000

어류군집을 이용한 생물보전지수(Index of Biological Integrity, IBI)와 서식지 평가지수 (qoalitativeHabitatEvaluationlndex, QHEI)를 적용하여 금호강의 수서 생태계를 평가하였다. 총체적으로 금호강의 IBI값은 13-37 범위에 있었으며, 연 평균값은 23(n=25, Std. error=1.16)으로서 Karr(1981) 와 U.S. EPA (1993) 기준에 따르면 "Poor" 또는 "Very Poor" 상태로 판명되었다. 평균 IBI값은 하천의 고도구배를 따라서 $0.22km^{-1}$($r^2$=0.91, p<0.05)로 감소하였다. 하류지역의 IBI값의 감소는 여울저서성 어류 및 식충성 어류의 감소와 함께 내성종, 비정상 어류 및 외래 어류의 증가 때문으로 판명되었다. IBI값의 공간적 양상은 평균 어종 수와 1차 함수관계 ($r^2$=0.998, p< 0.001)를 보인 QHEI와 동일한 양상을 보였다. 수 환경내 conservative ion변화의 척도로서 측정된 전기전도도와 pH값에 따르면, 금호강은 여름동안의 장마 및 수계로부터 표층수 유입으로 인해 30%까지 희석되었으며, 이런 결과는 장마기간 동안 강물의 물리적, 화학적 불안정성을 제시하였으며, 장마기간 및 장마 후의 IBI값을 비교해 보면 장마 전에 비해 20%이상 감소하였다. 총체적으로 하천의 물리적 교란 전(장마 전), 서식지 평가지수는 잡식성 어종의 상대 풍부도와 역상관관계(r=0.99, p<0.0001)를 보인 반면에 육식성 어종과는 정상관관계(r=0.87, p=0.05)를 보였다. 결론적으로 서식지의 공간적 질적 저하는 영양구조 체제에 변경을 초래하였고, 이런 기능적 변화는 결국 IBI값의 감소를 초래하였다.

• Journal of Microbiology and Biotechnology
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• 제29권12호
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• pp.1947-1956
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• 2019

The gut microbiome influences the health and well-being of dogs. However, little is known about the impact of breed on the fecal microbiome composition in dogs. Therefore, we aimed to investigate the differences in the fecal microbiome in three breeds of dog fed and housed under the same conditions, namely eight Maltese (8.0 ± 0.1 years), eight Miniature Schnauzer (8.0 ± 0.0 years), and nine Poodle dogs (8.0 ± 0.0 years). Fresh fecal samples were collected from the dogs and used to extract metagenomic DNA. The composition of the fecal microbiome was evaluated by 16S rRNA gene amplicon sequencing on the MiSeq platform. A total of 840,501 sequences were obtained from the 25 fecal samples and classified as Firmicutes (32.3-97.3% of the total sequences), Bacteroidetes (0.1-62.6%), Actinobacteria (0.2-14.7%), Fusobacteria (0.0-5.7%), and Proteobacteria (0.0-5.1%). The relative abundance of Firmicutes was significantly lower in the Maltese dog breed than that in the other two breeds, while that of Fusobacteria was significantly higher in the Maltese than in the Miniature Schnauzer breed. At the genus level, the relative abundance of Streptococcus, Fusobacterium, Turicibacter, Succinivibrio, and Anaerobiospirillum differed significantly among the three dog breeds. These genera had no correlation with age, diet, sex, body weight, vaccination history, or parasite protection history. Within a breed, some of these genera had a correlation with at least one blood chemistry value. This study indicates that the composition of the fecal microbiome in dogs is affected by breed.

• 한국환경농학회지
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• 제39권1호
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• pp.65-74
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• 2020

BACKGROUND: Soil carbon sequestration has been investigated for a long time because of its potential to mitigate the greenhouse effect. No- or reduced tillage, crop rotations, or cover crops have been investigated and practiced to sequester carbon in soils but the roles of soil biota, particularly microorganisms, have been mostly ignored although they affect the amount and stability of soil organic matters. METHODS AND RESULTS: In this study we analyzed the organic matter and microbial community in organically cultivated corn field soils where no-tillage (NT) or conventional tillage (CT) had been practiced for about three years. The amounts of organic matter and recalcitrant carbon pool were 18.3 g/kg dry soil and 4.1 g C/kg dry soil, respectively in NT soils, while they were 12.4 and 2.5, respectively in CT soils. The amounts of RNA and DNA, and the copy numbers of bacterial 16S rRNA genes and fungal ITS sequences were higher in NT soils than in CT soils. No-tillage treatment increased the diversities of soil bacterial and fungal communities and clearly shifted the bacterial and fungal community structures. In NT soils the relative abundances of bacterial phyla known as copiotrophs, Betaproteobacteria and Bacteroidetes, increased while those known as oligotrophs, Acidobacteria and Verrucomicrobia, decreased compared to CT soils. The relative abundance of a fungal phylum, Glomeromycota, whose members are known as arbuscular mycorrhizal fungi, was about two time higher in NT soils than in CT soils, suggesting that the higher amount of organic matter in NT soils is related to its abundance. CONCLUSION: This study shows that no-tillage treatment greatly affects soil microbial abundance and community structure, which may affect the amount and stability of soil organic matter.

• Asian-Australasian Journal of Animal Sciences
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• 제29권4호
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• pp.500-508
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• 2016

This study was conducted to investigate the effects of Momordica charantia saponin (MCS) on ruminal fermentation of maize stover and abundance of selected microbial populations in vitro. Five levels of MCS supplements (0, 0.01, 0.06, 0.30, 0.60 mg/mL) were tested. The pH, $NH_3-N$, and volatile fatty acid were measured at 6, 24, 48 h of in vitro mixed incubation fluids, whilst the selected microbial populations were determined at 6 and 24 h. The high dose of MCS increased the initial fractional rate of degradation at t-value = 0 ($FRD_0$) and the fractional rate of gas production (k), but decreased the theoretical maximum of gas production ($V_F$) and the half-life ($t_{0.5}$) compared with the control. The $NH_3-N$ concentration reached the lowest concentration with 0.01 mg MCS/mL at 6 h. The MSC inclusion increased (p<0.001) the molar proportion of butyrate, isovalerate at 24 h and 48 h, and the molar proportion of acetate at 24 h, but then decreased (p<0.05) them at 48 h. The molar proportion of valerate was increased (p<0.05) at 24 h. The acetate to propionate ratio (A/P; linear, p<0.01) was increased at 24 h, but reached the least value at the level of 0.30 mg/mL MCS. The MCS inclusion decreased (p<0.05) the molar proportion of propionate at 24 h and then increased it at 48 h. The concentration of total volatile fatty acid was decreased (p<0.001) at 24 h, but reached the greatest concentration at the level of 0.01 mg/mL and the least concentration at the level of 0.60 mg/mL. The relative abundance of Ruminococcus albus was increased at 6 h and 24 h, and the relative abundance of Fibrobacter succinogenes was the lowest (p<0.05) at 0.60 mg/mL at 6 h and 24 h. The relative abundance of Butyrivibrio fibrisolvens and fungus reached the greatest value (p<0.05) at low doses of MCS inclusion and the least value (p<0.05) at 0.60 mg/mL at 24 h. The present results demonstrates that a high level of MCS quickly inhibits in vitro fermentation of maize stover, while MCS at low doses has the ability to modulate the ruminal fermentation pattern by regulating the number of functional rumen microbes including cellulolytic bacteria and fungi populations, and may have potential as a feed additive applied in the diets of ruminants.

• 한국유기농업학회지
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• 제28권2호
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• pp.235-250
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• 2020

작물 재배 방법이 토양의 미생물 군집 특성과 화학성에 미치는 영향을 검토하였다. 이를 위해서 다섯 곳의 고추 관행 재배지와 다섯 곳의 유기농 재배지 토양을 채취한 후, 16S rRNA 유전자 기반의 파이로시퀀싱 기법으로 미생물 군집을 조사하였다. 분석 결과 총 22개의 세균 문으로 구성되었으며 Proteobacteria 문(33.0 ± 5.7%), Actinobacteria 문(19.9 ± 9.7%) 및 Firmicutes 문(13.6 ± 5.0%)이 우점하였고, 이들은 전체 상대풍부도의 66%를 차지하였다. 고추 관행 재배지와 유기농 재배지의 미생물 군집 분포를 비교했을 때 전반적으로 서로 다른 군집 특성을 나타내었다. 또한 관행 재배 토양에서는 Actinobacteria 문과 Chloroflexi 문이 상대적으로 풍부하였고, 유기 재배 토양에서는 Proteobacteria 문과 Firimicutes 문이 상대적으로 풍부하였다. 특히 Streptomyces 속과 Bacillus 속의 상대풍부도는 관행 재배 토양과 유기 재배 토양 간에 상당한 차이를 보였다. 또한 토양 화학 성에 의하여 세균 군집 변화가 관찰되었는데, Proteobacteria 문의 Rhizobiales 목과 Actinobacteria 문의 Streptomyces 속은 pH에 의해 세균 군집이 바뀌었고, Firimicutes 문의 Bacillus 속은 유기물 함량에 의해 군집 분포가 바뀌었다. 본 연구결과는 재배관리에 따른 토양의 물리-화학성의 변화가 미생물 군집 분포에 뚜렷하게 관련(p<0.05)되어 있다는 것을 보여주었다.