• Journal of Microbiology and Biotechnology
• /
• 제28권7호
• /
• pp.1156-1167
• /
• 2018

The aim of this study was to isolate and characterize lead (Pb)-solubilizing bacteria from heavy metal-contaminated mine soils and to evaluate their inoculation effects on the growth and Pb absorption of Brassica juncea. The isolates were also evaluated for their plant growth-promoting characteristics as well as heavy metal and salt tolerance. A total of 171 Pb-tolerant isolates were identified, of which only 15 bacterial strains were able to produce clear haloes in solid medium containing PbO or $PbCO_3$, indicating Pb solubilization. All of these 15 strains were also able to dissolve the Pb minerals in a liquid medium, which was accompanied by significant decreases in pH values of the medium. Based on 16S rRNA gene sequence analysis, the Pb-solubilizing strains belonged to genera Bacillus, Paenibacillus, Brevibacterium, and Staphylococcus. A majority of the Pb-solubilizing strains were able to produce indole acetic acid and siderophores to different extents. Two of the Pb-solubilizing isolates were able to solubilize inorganic phosphate as well. Some of the strains displayed tolerance to different heavy metals and to salt stress and were able to grow in a wide pH range. Inoculation with two selected Pb-solubilizing and plant growth-promoting strains, (i.e., Brevibacterium frigoritolerans YSP40 and Bacillus paralicheniformis YSP151) and their consortium enhanced the growth and Pb uptake of B. juncea plants grown in a metal-contaminated soil. The bacterial strains isolated in this study are promising candidates to develop novel microbe-assisted phytoremediation strategies for metal-contaminated soils.

• 한국환경농학회지
• /
• 제26권4호
• /
• pp.332-336
• /
• 2007

Pseudomonas stutzeri strain KCCM 34719 was used in this experiment to determine the effects of increasing Pb(II) concentrations on its growth rate. To obtain optimum growth conditions, strain KCCM 34719 was cultivated in nutrient broth under various conditions, such as temperature, pH, and NaCl concentration. Optimal conditions for cell growth were $30^{\circ}C$ of temperature, 8.0 of pH, and 3% of NaCl concentration, respectively. Growth response of bacterial cell to Pb(II) showed tolerance to concentrations ranging from 10 to 100 mg ${\ell}^{-1}$ in liquid culture, following a growth pattern similar to the control. Growth rate was greatly inhibited at 200 mg ${\ell}^{-1}$ of Pb(II).

• 한국환경보건학회지
• /
• 제15권1호
• /
• pp.63-73
• /
• 1989

The purposes of this study were to find out the heavy metal and antibiotic resistant coliform bacteria from mineral water and the resistant factors. For the experiment, mineral water samples were taken from A area and B area during the period from march to July, 1988. The results of the experiment were as follows 1. From mineral water, eleven resistant coliforms and one susceptible coliform were isolated. 2. All resistant isolates harbored diverse plasmids of ranged ca. 14-54kb. 3. Susceptible coliform harbored a only plasmid of ca. 2.8 kb. 4. All resistant isolates harbored common size of plasmid of ca. 14kb. 5. As a result of the transformation and agarose gel electrophoresis experiments, resistant factor was R-plasmid. In conclusion, It is suggested that heavy metal contamination of mineral water is the selective pressure for the plasmid encoding the tolerance. Heavy metal resistance, in some case, is present with antibiotic resistance. Therefore, heavy metal contamination of mineral water induces antibiotic resistant bacteria.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1995년도 춘계학술대회 논문집
• /
• pp.157-163
• /
• 1995

This paper presents an algorithm to deternine the tool path height for rough machining of sculptured surface. To minimize rough machining of sculptured surface, it is necessary to determine the tool path heights of contour planes. the proposed algorithm searches for the height at which maximum metal removal rate is obtained. This bisection method is accomplished until all shoulder heights are within roughing tolerance. The machining experiment demonstrates the superiority of the algorithm presented in this thesis.

• 한국환경농학회지
• /
• 제18권1호
• /
• pp.28-34
• /
• 1999

전국의 16개 휴 ${\cdot}$ 폐광 지역에서 토양중 중금속함량과 식생조사를 실시한 결과를 요약하면 다음과 같다. 조사 휴 ${\cdot}$ 폐광산 대부분의 경우 피복식물이 없는 나대지로 존재하고 있었고 유기물함량, CEC 등이 낮은 값을 가지고 있는 등 대체로 척박한 토양조건을 가지고 있었으며 특정 중금속으로 인한 오염의 정도가 토양환경보전법상의 우려기준과 대책기준을 초과하는 지점도 있었다. 식물종들의 분포를 조사한 결과 목본은 소나무, 아카시나무 등이, 초본은 쑥과 억새의 출현빈도가 높았다. 쑥은 지상부에 Zn과 Cd를 각각 1,191, 26.35mg/kg을 함유하였고, 패랭이꽃은 Cu를 405mg/kg 함유하여 체내 농도가 가장 높은 것으로 조사되었다. 체내 중금속함량, 건물생산량, 생육기간등을 고려할 때 쑥, 억새, 달맞이꽃등이 토양정화식물로서의 가치가 있다고 생각된다. 앞으로 쑥을 비롯한 내성이 있는 식물종에 대한 조사는 물론 생리적 특성, 토양조건, 기후조건 등에 대한 지속적 연구가 뒤따라야 할 것으로 생각된다.

• The Korean Journal of Ecology
• /
• 제21권3호
• /
• pp.225-231
• /
• 1998

The studies on the potentiality of biomonitoring heavy metal pollution in coastal region of industrial complex were performed to investigate the heavy metal accumulation and induction of metal-binding protein (MBP) as detoxification process using Rumex maritimus. Bioconcentration in organs and MBP in root of R. maritimus was investigated for the research of the tolerance of heavy metals. The bioconcentration of cadmium and zinc in organs showed 3.6-8.0 times in root higher than in shoot, so it was found that heavy metal accumulated selectively in root. MBP increased absorbance in 254 nm and decreased in 280 nm, because it was composed of high cystein content and low aromatic acids, so absorbance had large difference between 254 nm and 280 nm. The existence of MBP in the 10-20 fraction was ascertained with anion exchange chromatography and it was identified that concentration of heavy metal increased according as an exposure concentration of medium increased in QAE Sephadex A-25 elution profile. These results suggested that MBP could play a role in biomarker determining the bioconcentration of plant. This study demonstrated a possibility that removal ability of heavy metal of R. maritimus resulted from detoxification process and MBP could be utilized as a biomarker of heavy metal pollution.

• Journal of Microbiology and Biotechnology
• /
• 제18권7호
• /
• pp.1298-1307
• /
• 2008

In this study, we investigated the inhibition effects of single and mixed heavy metal ions ($Zn^{2+},\;Ni^{2+},\;Cu^{2+},\;and\;Cd^{2+}$) on iron oxidation by Acidithiobacillus ferrooxidans. Effects of metals on the iron oxidation activity of A. ferrooxidans are categorized into four types of patterns according to its oxidation behavior. The results indicated that the inhibition effects of the metals on the iron oxidation activity were noncompetitive inhibitions. We proposed a reduced inhibition model, along with the reduced inhibition constant ($\alpha_i$), which was derived from the inhibition constant ($K_I$) of individual metals and represented the tolerance of a given inhibitor relative to that of a reference inhibitor. This model was used to evaluate the toxicity effect (inhibition effect) of metals on the iron oxidation activity of A. ferrooxidans. The model revealed that the iron oxidation behavior of the metals, regardless of metal systems (single, binary, ternary, or quaternary), is closely matched to that of any reference inhibitor at the same reduced inhibition concentration, $[I]_{reduced}$, which defines the ratio of the inhibitor concentration to the reduced inhibition constant. The model demonstrated that single metal systems and mixed metal systems with the same reduced inhibitor concentrations have similar toxic effects on microbial activity.

• Journal of Mechanical Science and Technology
• /
• 제20권10호
• /
• pp.1680-1690
• /
• 2006

As a promising and novel manufacturing technology, laser aided direct metal deposition (DMD) process produces near-net-shape functional metal parts directly from 3-D CAD models by repeating laser cladding layer by layer. The key of the build-up mechanism is the effective control of powder delivery and laser power to be irradiated into the melt-pool. A feedback control system using two sets of optical height sensors is designed for monitoring the melt-pool and real-time control of deposition dimension. With the feedback height control system, the dimensions of part can be controlled within designed tolerance maintaining real time control of each layer thickness. Clad nugget shapes reveal that the feedback control can affect the nugget size and morphology of microstructure. The pore/void level can be controlled by utilizing pulsed-mode laser and proper design of deposition tool-path. With the present configuration of the control system, it is believed that more innovation of the DMD process is possible to the deposition of layers in 3-D slice.

• 문화기술의 융합
• /
• 제5권4호
• /
• pp.373-378
• /
• 2019

해양지역에서는 토양의 염 농도가 증가하고 내륙지역은 중금속 오염으로 식물의 피해가 따라서 증가한다. 내륙의 산업 발달 지역에서는 Co, Ni, Zn, 등 중금속이 축적되어 제거하거나, 내성을 갖은 식물의 유전자원 연구가 절실히 요구되고 있다. 앞의 두 가지 문제점은 공히 식물 뿌리에 스트레스를 야기하기에 가능성 있는 식물을 찾기에 과학자들이 많은 노력을 해오고 있다. 본 연구에서는 내염식물로 알려진 것으로 해안가 근처에서 채집 되어진 섬갯장대(Arabis stelleri var. japonica)의 종자를 발아하여 사용하였다. 동일한 과이면서 모든 유전자가 밝혀졌고, 표본식물인 애기장대 종자를 실험재료로 사용하여 실험실 배양 조건 하에서 성장발육과 내성을 비교 연구하였다. 그 결과 250 uM Nickle과 cobalt에서 3배 정도 내성을 나타내었고,1mM 아연에서는 4배 이상의 내성을 섬갯장대에서 나타내었다. Na염에 대한 내성은 50mM 농도에서 20%이상 발육이 증가하여서 중금속과 염농도에 내성을 보였다. 세포내 기작을 연구하기 위한 준비로서 Na 이온의 체내 축적을 측정하였다. 그 결과 내성을 갖은 섬갯장대 경엽부에서 더욱 감소하는 결과를 보였다. 이는 측적하는 기작보다는 배출하는 유전자의 활성이 중요하다고 사료된다.

• 한국환경농학회지
• /
• 제33권2호
• /
• pp.129-133
• /
• 2014

BACKGROUND: This study was performed for selecting yeast mutants with a high tolerance for targeted metals, and determining whether yeasts strains tolerant to multiple heavy metals could be induced by sequential adaptations. METHODS AND RESULTS: A mutant yeast strain tolerant to the heavy metals cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) was selected by sequential elevated exposures to each metal with intermittent mutant isolation steps. A Cd-tolerant mutant was isolated by growing yeast cells in media containing $CdCl_2$ concentrations that were gradually increased to 1 mM. Then the Cd-tolerant mutant was gradually exposed to increasing levels of $CuCl_2$ in growth media until a concentration of 7 mM was reached, thus generating a strain tolerant to both Cd and Cu. In the subsequent steps, this mutant was exposed to $NiCl_2$ (up to 8 mM), and a resultant isolate was further exposed to $ZnCl_2$ (up to 60 mM), allowing the derivation of a yeast mutant that was simultaneously tolerant to Cd, Cu, Ni, and Zn. CONCLUSION: This method of inducing tolerance to multiple targeted heavy metals in yeast will be useful in the bioremediation of heavy metals.