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Bacterial and fungal community composition across the soil depth profiles in a fallow field
Ko, Daegeun,Yoo, Gayoung,Yun, Seong-Taek,Jun, Seong-Chun,Chung, Haegeun The Ecological Society of Korea 2017 Journal of Ecology and Environment Vol.41 No.9
Background: Soil microorganisms play key roles in nutrient cycling and are distributed throughout the soil profile. Currently, there is little information about the characteristics of the microbial communities along the soil depth because most studies focus on microorganisms inhabiting the soil surface. To better understand the functions and composition of microbial communities and the biogeochemical factors that shape them at different soil depths, we analyzed microbial activities and bacterial and fungal community composition in soils up to a 120 cm depth at a fallow field located in central Korea. To examine the vertical difference of microbial activities and community composition, ${\beta}$-1,4-glucosidase, cellobiohydrolase, ${\beta}$-1,4-xylosidase, ${\beta}$-1,4-N-acetylglucosaminidase, and acid phosphatase activities were analyzed and barcoded pyrosequencing of 16S rRNA genes (bacteria) and internal transcribed spacer region (fungi) was conducted. Results: The activity of all the soil enzymes analyzed, along with soil C concentration, declined with soil depth. For example, acid phosphatase activity was $125.9({\pm}5.7({\pm}1SE))$, $30.9({\pm}0.9)$, $15.7({\pm}0.6)$, $6.7({\pm}0.9)$, and $3.3({\pm}0.3)nmol\;g^{-1}\;h^{-1}$ at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively. Among the bacterial groups, the abundance of Proteobacteria (38.5, 23.2, 23.3, 26.1, and 17.5% at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively) and Firmicutes (12.8, 11.3, 8.6, 4.3, and 0.4% at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively) decreased with soil depth. On the other hand, the abundance of Ascomycota (51.2, 48.6, 65.7, 46.1, and 45.7% at 15, 30, 60, 90, and 120 cm depths, respectively), a dominant fungal group at this site, showed no clear trend along the soil profile. Conclusions: Our results show that soil C availability can determine soil enzyme activity at different soil depths and that bacterial communities have a clear trend along the soil depth at this study site. These metagenomics studies, along with other studies on microbial functions, are expected to enhance our understanding on the complexity of soil microbial communities and their relationship with biogeochemical factors.
Safe and Feasibility of Continuous Ketamine Infusion for Analgosedation in Medical ICU Patients
( Ryoung-eun Ko ),( Chi Ryang Chung ),( Jihoon Jang ),( Sungmin Hong ),( Bo-guen Kim ),( Ju Yeun Song ),( Daegeun Lee ),( Gee Young Suh ) 대한결핵 및 호흡기학회 2021 대한결핵 및 호흡기학회 추계학술대회 초록집 Vol.129 No.-
Background Some mechanical ventilated patients require deep sedation during acute respiratory distress syndrome management, and these patients frequently received opioids, benzodiazepine, and propofol. Recent meta-analysis has reported an increasing trend of ketamine use in mechanically ventilated patients and showed that ketamine may be play a role as a sedative-sparing agent. However, most previous continuous ketamine studies were conducted in patients with traumatic, post-operative, or cerebral ischemia with small sample sizes. This study conducted to assess the effect of continuous ketamine in patients who admitted medical or cardiac ICUs and received mechanical ventilator. Methods We conducted a retrospective cohort study between March 2012 and June 2020 at Samsung Medical Center. Adult patients who received mechanical ventilation support over 24 hours and received continuous ketamine infusion at least 8 hours were included. Results Of all 12,534 medical or cardiac ICU patients, 564 were eligible for analysis. Ketamine was used 33.3 (19.0-67.5) hours and median continuous infusion dose was 0.11 (0.06-0.23) mcg/kg/hr. Of all patients, 469 (83.2%) received continuous ketamine infusion concomitant with analgosedation. Blood pressure, and vasopressor inotropic score were not changed before and after continuous ketamine infusion. Heart rate was decreased significantly from 106.9 (91.4-120.9) in 8 hours prior- and to 99.8 (83.9-114.4) in 24 hours post-ketamine initiation. In addition, respiratory rate was decreased significantly from 21.7 (18.6-25.4) in 8 hours prior- and to 20.1 (17.0-23.0) in 24 hours post-ketamine initiation. Overall opioid usage was significantly reduced; 3.0 (0.0-6.0) mcg/kg/hr as fentanyl equivalent dose in 8 hours prior- and to 1.0 (0.0-4.1) mcg/kg/hr as fentanyl equivalent dose in 24 hours post-ketamine initiation. However, the use of sedatives and antipsychotic medication were not decreased. Conclusions Ketamine may be a safe and feasible analgesic for medical or cardiac ICU patients as an opioid sparing agent without adverse hemodynamic effects.
He, Wenmei,Kim, Youjin,Ko, Daegeun,Yun, Seongtaek,Jun, Seongchun,Yoo, Gayoung Elsevier 2019 Science of the Total Environment Vol.690 No.-
<P><B>Abstract</B></P> <P>Potential CO<SUB>2</SUB> leakage is a major concern for carbon capture and storage (CCS). The effects of high soil CO<SUB>2</SUB> concentration on microbes is a major element of impact assessments of CO<SUB>2</SUB> leakage on terrestrial ecosystems. We conducted a field experiment to investigate the responses of microbial functional groups of ammonia-oxidizers, methanogens, and methanotrophs in high soil CO<SUB>2</SUB> conditions. A single-point injection gassing plot (2.5 m × 2.5 m in size), which had 52.2% CO<SUB>2</SUB> in the center (radius = 0.5 m) and 5.5% in the edge (radius = 1.7 m) at 10 cm depth, was employed. N<SUB>2</SUB>O and CH<SUB>4</SUB> emissions increased after 1 day of injection because injected CO<SUB>2</SUB> was instantly utilized by nitrifiers and methanogens. This suggests that the activities of the selected microbes could be stimulated by high soil CO<SUB>2</SUB> concentrations. Prolonged CO<SUB>2</SUB> injection has toxic effects on aerobic nitrifiers, but may favor anaerobic methanogens. However, the early stimulatory effects of high soil CO<SUB>2</SUB> on N<SUB>2</SUB>O and CH<SUB>4</SUB> production did not last to the end of injection. These results imply that increased N<SUB>2</SUB>O and CH<SUB>4</SUB> emissions could be the minor side effects of high soil CO<SUB>2</SUB>. Microbes responded faster than plants to high soil CO<SUB>2</SUB>, with responses observed as late as 7 days after injection. The inhibition of plant absorption of soil water and nutrients by high soil CO<SUB>2</SUB> concentrations may also influence microbial responses. Moreover, high soil water content could retard underground CO<SUB>2</SUB> diffusion, which would magnify CO<SUB>2</SUB> impacts on plants and microbes. Our results suggest that microbial response could be used as an early indicator of the impact assessments of CO<SUB>2</SUB> leakage on soil ecosystems. An understanding of the interaction among soils, plants, and microbes would be helpful in assessing the biological risks of potential CO<SUB>2</SUB> leakage.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Extremely high (52.2%) and moderately high (5.5%) soil CO<SUB>2</SUB> concentrations enhanced N<SUB>2</SUB>O and CH<SUB>4</SUB> emissions. </LI> <LI> One-day responses of microbes were much faster than those of plants (seven days). </LI> <LI> Prolonged high soil CO<SUB>2</SUB> concentration negatively affected ammonia-oxidizer populations, but these microbes can recover after injection stopped. </LI> <LI> High soil CO<SUB>2</SUB> concentrations were favorable to methanogens. </LI> <LI> Interactions among high soil CO<SUB>2</SUB>, soil water, plants, and microbes were newly illuminated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Effects of silver-graphene oxide nanocomposites on soil microbial communities
Kim, Min-Ji,Ko, Daegeun,Ko, Kwanyoung,Kim, Dawon,Lee, Ji-Yeon,Woo, Sang Myeong,Kim, Woong,Chung, Haegeun Elsevier 2018 Journal of hazardous materials Vol.346 No.-
<P><B>Abstract</B></P> <P>Due to the application of silver-graphene oxide (Ag-GO) in diverse fields, it is important to investigate its potential impacts on the environment including soils. In this study, the response of microbial communities in soils treated with Ag-GO synthesized by glucose reduction was determined by analyzing enzyme activities, biomass, and inorganic N concentrations and by pyrosequencing. In soils treated with 0.1–1mg Ag-GO g<SUP>−1</SUP> soil, the activities of β-glucosidase, cellobiohydrolase, and xylosidase decreased up to 80% and NO<SUB>3</SUB> <SUP>−</SUP> concentration decreased up to 82% indicating inhibited nitrification. Within the bacterial community, the relative abundance of <I>Acidobacteria</I> and <I>Cyanobacteria</I> in soils treated with Ag-GO were lower than that in control soil. Meanwhile, the relative abundance of <I>AD3</I> and <I>Firmicutes</I> tended to increase under Ag-GO treatments. These changes in bacterial community composition reflected lowered activities associated with C and N cycling. On the other hand, microbial biomass showed no distinct change in response to Ag-GO treatment. Our study can serve as important basis in establishing guidelines for regulating the release of nanocomposites such as Ag-GO to the soil environment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The response of microbial communities in soils treated with 0.1–1mgg<SUP>−1</SUP> soil Ag-GO was determined. </LI> <LI> Ag-GO significantly lowered C-cycling enzyme activity and inhibited nitrification. </LI> <LI> Ag-GO decreased the relative abundance of <I>Acidobacteria</I> and <I>Cyanobacteria</I> while it increased that of <I>Firmicutes</I>. </LI> <LI> Ag-GO can negatively affect soil microbial activity associated with C and N cycling and alter bacterial community composition. </LI> </UL> </P>
오정석(Jeongseog Oh),노동순(Dongsoon Noh),이대근(Daegeun Lee),양제복(Jebok Yang),고창복(Changbok Ko) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.43
The non-premixed Oxy-CH₄ flame characteristics were studied in a lab-scale slot burner for industrial furnace design. To estimate the flame stabilization, flow velocity was varied upto uF=50 ㎧ for methane gas and uOx= 100 ㎧ for oxygen gas. The flame stabilization curve showed that lifted flame region became broaden with oxygen inlet temperature (TOx) increase and slot separation width decrease. In addition, the carbon-dioxide (CO₂) dilution to oxidant debilitated the flame stabilization due to reduced oxidant concentration and chemical reaction.