• 한국토양비료학회지
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• 제49권1호
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• pp.17-29
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• 2016

Though there is an abundant supply of nitrogen in the atmosphere, it cannot be used directly by the biological systems since it has to be combined with the element hydrogen before their incorporation. This process of nitrogen fixation ($N_2$-fixation) may be accomplished either chemically or biologically. Between the two elements, biological nitrogen fixation (BNF) is a microbiological process that converts atmospheric di-nitrogen ($N_2$) into plant-usable form. In this review, the genetics and mechanism of nitrogen fixation including genes responsible for it, their types and role in BNF are discussed in detail. Nitrogen fixation in the different agricultural systems using different methods is discussed to understand the actual rather than the potential $N_2$-fixation procedure. The mechanism by which the diazotrophic bacteria improve plant growth apart from nitrogen fixation such as inhibition of plant ethylene synthesis, improvement of nutrient uptake, stress tolerance enhancement, solubilization of inorganic phosphate and mineralization of organic phosphate is also discussed. Role of diazotrophic bacteria in the enhancement of nitrogen fixation is also dealt with suitable examples. This mini review attempts to address the importance of diazotrophic bacteria in nitrogen fixation and plant growth improvement.

• Environmental Engineering Research
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• 제12권4호
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• pp.136-147
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• 2007

In an effort to identify possible microbes for seeking bioagents for remediation of herbicide-contaminated soils, seven species of phototrophic nonsulfur bacteria (Rhodobacter capsulatus and sphaeroides, Rhodospirillum rubrum, Rhodopseudomonas acidophila, blastica and viridis, Rhodomicrobium vannielii) were grown in the presence of the herbicide, butachlor, and bacterial growth rates and nitrogen fixation were measured with different carbon sources. Under general conditions, all species showed 17-53% reductions in growth rate following butachlor treatment. Under nitrogen-fixing conditions, Rb. capsulatus and Rs. rubrum showed 1-4% increases in the growth rates and 2-10% increases in nitrogen-fixing abilities, while the other 5 species showed decreases of 17-47% and 17-85%, respectively. The finding that Rp. acidophila, Rp. blastica, Rp. viridis and Rm. vannielii showed stronger inhibitions of nitrogenase activity seems to indicate that species in genera Rhodobacter and Rhodospirillum are less influenced by butachlor than those in Rhodopseudomonas and Rhodomicrobium in terms of nitrogen-fixing ability. Overall, nitrogenase activity was closely correlated with both growth rate and glutamine synthetase activity (representing nitrogen metabolism). When the carbon sources were compared, pyruvate (three carbons) was best for all species in terms of growth rate and nitrogen fixation, with malate (four carbons) showing intermediate values and ribose(five carbons) showing the lowest; these trends did not change in response to butachlor treatment. We verified that each of the 7 species had a plasmid ($12.2{\sim}23.5\;Kb$). We found that all 7 species could use butachlor as a sole carbon source and 3 species were controlled by plasmid-born genes, but it is doubtful whether plasmid-born genes were responsible to nitrogen fixation.

• 한국환경농학회지
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• 제27권4호
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• pp.362-367
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• 2008

The legume-rhizobia symbiosis is an important source of plant growth and nitrogen fixation for many agricultural systems. This study was conducted to investigate the effects of salinity stress on nitrogen fixation and growth of pea (Pisum sativum L.), which has antimutagenic activities against chemical mutagen, inoculated with R. leguminosarum bv. viciae cultured with additional plant-to-rhizobia signal compounds, naringenin (NA,15 uM), methyl-jasmonate (MJ, 50 uM) or both, under greenhouse conditions. Three salinity levels (0.6, 3.0 and $6.0\;dS\;m^{-1}$) were imposed at 3 days after transplanting and maintained through daily irrigations. Addition of signal compounds under non-stress and stress conditions increased dry weight, nodule numbers, leaf area and leaf greenness. The inducers increased photosynthetic rate under non-stress and stress conditions, by approximately 5-20% when compared to that of the non-induced control treatment. Under stress conditions, proline content was less in plants treated with plant-to-bacteria signals than the control, but phenol content was significantly increased, compared to that of the control. The study suggested that pre-incubation of bacterial cells with plant-to-bacteria signals could enhance pea growth, photosynthesis, nitrogen fixation and biomass under salinity stress conditions.

• 한국미생물·생명공학회지
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• 제46권2호
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• pp.154-161
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• 2018

현재 도시의 도시열섬현상을 완화시키는 방안으로 도시 녹화사업 및 연구가 주목 받고 있다. 이 연구에서는 질소고정균을 분리하고, 식물 성장에 미치는 영향을 확인했다. 먼저 질소고정 균을 분리하기 위해, 질소원이 없는 배지에서 enrichment를 실시했고, 질소원이 제한된 배지에서 높은 성장을 보인 colony를 분리하여 순수분리 했다. 순수 분리된 균은 ARA를 통해 acetylene이 90% 이상 감소되고, ethylene 생성을 통해 nitrogenase의 활성을 간접적으로 확인했다. 재현성이 확인된 Cedecea sp. MK7과 Enterobacter sp. Y8을 선별했다. 선별된 질소고정 균을 perennial rye grass의 성장에 적용한 결과 건조중량이 18.65 mg인 대조군에 비해 34.80 mg (186.60%)으로 증가한 것을 확인했다. 식물 성장 후, 질소고정 균이 접종된 토양의 미생물 군집 분석은 대조군과 유사했다. 따라서 본 연구에서는 도시녹화 시스템에 질소고정 균을 이용하여 식물 성장을 촉진한다면 그 효율이 증대될 것이다.

• 미생물학회지
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• 제21권2호
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• pp.71-78
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• 1983

The number of aerobic free-living nitrogen fixation bacteria and factors in soil at different stands covered with Pinus rigida, Quercus acutissima and Zoysia japonica in Cheongju area were investigated from Feb. to Sept 1981. 1. The numbers of $N_2-fixation$ bacteria, according to the seasonal changes, increased gradually from winter to spring and summer. But the growth pattern revealed some differences in accordance with plant cover stands : the numbers increased abruptly in May at Pinus, May-June at Quercus and Apr. May at Zoysia stand. The pick of numbers represented in Aug. Sept, at Pinus, Jul-Aug. at Quercus and May-Jun. at Zoysia stand, respectively. 2. The interrelationship between the monthly changes of enviotnmental factors and numbers of $N_2-fixation$ bacteria at different stands, mainly depends upon the soil temperature than other soil factors (r=0.71-0.84). The numbers of $N_2-fixation$ bacteria may increase 5-7 times according to increase $10^{\circ}C$ of soil temperature, and optimal range was $20{\sim}30^{\circ}C$ for growth. Equation of the interrelation between soil temperature and numbers could be stated as follows : log y=ax+b. 3. In the case of high soil temperature, the bacterial numbers presented high level in drought periods. Therefore, the $N_2-fixation$ bacterial species in these soil seem to consist of resistant to desication. 4. The influence of soil organic matter for growth of $N_2-fixation$ bacteria indicated low conrelation. The reason may seen the content of organic matter in these soil existed abundantly above the quantities of limitation for growth. 5. In artifical gradients, the $N_2-fixation$ bacteria were predominated at $20{\sim}30^{\circ}C$ same as natural condition, pH7-8, and 20-30% of soil water contents. 6. The vertical distribution of bacteria marked decreasing trends from surface to lower layers, and the decreasing degree was shown well in Zoysia, Quercus and Pinus stand in order. But in the trees, the numbers increased at 30cm layer estimated the region of root than 20cm layer. 7. Both catalase megative and positive group of $N_2-fixation$ bacteria in soil increased according to the rise of the soil temperature. Catalase positive group was revealed as dominant group in winter, and catalase negative group revealed in summer. The change of dominant pattern was shown during Feb. to Apr.

• Journal of Microbiology and Biotechnology
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• 제34권3호
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• pp.570-579
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• 2024

Root-nodule nitrogen-fixing bacteria are known for being specific to particular legumes. This study isolated the endophytic root-nodule bacteria from the nodules of legumes and examined them to determine whether they could be used to promote the formation of nodules in other legumes. Forty-six isolates were collected from five leguminous plants and screened for housekeeping (16S rRNA), nitrogen fixation (nifH), and nodulation (nodC) genes. Based on the 16S rRNA gene sequencing and phylogenetic analysis, the bacterial isolates WC15, WC16, WC24, and GM5 were identified as Rhizobium, Sphingomonas, Methylobacterium, and Bradyrhizobium, respectively. The four isolates were found to have the nifH gene, and the study confirmed that one isolate (GM5) had both the nifH and nodC genes. The Salkowski method was used to measure the isolated bacteria for their capacity to produce phytohormone indole acetic acid (IAA). Additional experiments were performed to examine the effect of the isolated bacteria on root morphology and nodulation. Among the four tested isolates, both WC24 and GM5 induced nodulation in Glycine max. The gene expression studies revealed that GM5 had a higher expression of the nifH gene. The existence and expression of the nitrogen-fixing genes implied that the tested strain had the ability to fix the atmospheric nitrogen. These findings demonstrated that a nitrogen-fixing bacterium, Methylobacterium (WC24), isolated from a Trifolium repens, induced the formation of root nodules in non-host leguminous plants (Glycine max). This suggested the potential application of these rhizobia as biofertilizer. Further studies are required to verify the N₂-fixing efficiency of the isolates.

• Applied Biological Chemistry
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• 제24권2호
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• pp.132-138
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• 1981

본 실험에서는 광합성세균(光合成細菌)의 검색(檢索)과 그 이용(利用)을 목적(目的)으로 우선 36개(個) 시료(試料)에서 광합성세균(光合成細菌)을 분리(分離)하고 그 세균(細菌)들의 성분(成分)과 질소(窒素) 고정력(固定力), 유기성(有機性) 폐수(廢水)의 정화능력(淨化能力)을 측정(測定)하였다. 일반적(一般的)으로 어느 시료(試料)나 광합성세균(光合成細菌)은 분포(分布)되어 있으며 분리(分離)된 균(菌)은 Rhodopseudomonas capsulatus, Rhodopseudomonas gelatinosa, 와 Rhodospirillum rubrum의 4종(種)이었다 이들의 질소(窒素) 고정력(固定力)은 균주(菌株)에 따라 다르고 R. capsulatus H-1가 가장 강(强)했다. 또한 유기성(有機性) 폐수(廢水)의 정화능력(淨化能力)은 폐수(廢水)와 균주(菌株)에 따라 다르게 나타났으나 일반적으로 상당(相當)히 강(强)한 정화능(淨化能)을 보여주고 있다.

• Current Research on Agriculture and Life Sciences
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• 제5권
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• pp.40-51
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• 1987

광교(光敎)를 비롯한 12개품종(個品種)의 대두근류(大豆根瘤)로부터 탐색분리(探索分離)한 질소고정균(窒素固定菌)의 생리적(生理的) 특성(特性) 및 숙주작물(宿主作物)과의 접종친화성(接種親和性)을 조사(調査)한 결과(結果)는 다음과 같다. 1. YMA배지(培地)에서 자란 질소고정균(窒素固定菌)의 색상(色相)은 백색상(白色相), 반투명색상(半透明色相), 투명색상(透明色相)이 각각(各各) 60%, 30%, 10%였으며 Litmus milk 반응(反應)은 alkali, acid serum, alkali serum, acid가 각각(各各) 51%, 29%, 9%, 11%로 나타났다. 2. 우량질소고정균(優良窒素固定菌)의 YM배지(培地)에서의 생육속도(生育速度) 및 pH의 변화(變化)는 S 022, S 096이 생육속도(生育速度)가 느리고, alkali를 생성(生成)하였으며 S 080, S 090, S 118은생육속도(生育速度)가 빠르고 산(酸)을 생성(生成)하였다. 3. YM배지(培地)의 초기(初期) pH가 6.0~7.0의 범위(範圍)에서 Rhizobia의 생육(生育)이 가장 좋았다. 4. 질소원(窒素源)으로서 glutamine, asparagine, allantion 등(等)은 Rhizobia의 생육(生育)을 촉진(促進)시켰다. 5. 분리(分離)한 균주(菌株) 전부(全部)가 대두(大豆)에 근류(根瘤)를 형성(形成)시켰으며, 우량질소고정균주(優良窒素固定菌株)는 그중 색상(色相)이 백색(白色)이고 colony가 소형(小型)이며 질산환원력(窒酸還元力)이 있고 아질산환원력(亞窒酸還元力)이 없으나 비교적(比較的) 높은 질소고정력(窒素固定力)을 나타냈다. 6. 동일균주(同一菌株)라도 숙주작물(宿主作物)의 친화성(親和性)에 따라서 질소고정능력(窒素固定能力)에 차이(差異)가 있었으며, 질소고정능력(窒素固定能力)이 없는 무효근류(無效根瘤)를 형성(形成)하는 균주(菌株)도 있었다.

• 한국토양비료학회지
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• 제20권1호
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• pp.69-76
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• 1987

The aerobic heterotrophic bacteria in the histosphere associated with grasses (Gramineae, Caryphyllaceae, Crucifereae) and rice cultivars in saline and reclaimed saline paddy soils were varied with species and rice cultivars. The fraction of aerobic heterotrophic $N_2$-fixing bacteria to the total aerobic heterotrophic bacteria were averaged to eighteen percent in the histosphere of grasses and rice. Acetylene reducing activity of these bacteria were ranged from 1 to 24 n mole/tube/hr. Most of the bacteria strains were predominated of hydrogen utilizing bacteria. The majority of these bacteria were closed to Pseudomonas, Azospirillum, Klebsiella and Agrobacter.

• 미생물학회지
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• 제37권2호
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• pp.114-119
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• 2001

산림토양의 각 토양층으로부터 분리된 세균 중에는 통상 농도의 NB배지에서는 중식이 현저히 저해되고 희석한 DNB 배지에서만 중식이 가능한 세균이 다수 포 되어 있었으며, 이들 세균은 NB배지를 $10^{-1}$~$10^{-4}$배로 희석한 배지에서의 증식양상에 따라 4가지형으로 구분되었다. 본 연구에서는 저영양세균의 기준에 따라 $10^{-4}$NB(1 mg C/liter)배지에서 양호하게 증식하는 Type II와 IV세균을 저영양세균으로 분류하였고, 60개의 Type IV(편성저영양세균; obligate oligotrophic bacteria)균주를 순수분리 하였다. 이들 저영양성 세균중 질소고정능을 갖는 11균주에 대하여 화학분류 및 계통분류학적 특성을 검토한 결과 모든 균주는 주요 균체지방산으로 $C_{18:1}$)을, 퀴논종은 Q-10을 함유하였으며, G+C함량은 61-64 mol%범위를 나타내었다. 16S rDNA염기서열을 결정한 결과 각 균주는 Proteobacteria $\alpha$-subdivision의 BANA domain (Bradyrhizobium, Agromonas, Nitrobacter 및 Afipia)에 속하였고 Bradyrhizobium japonicum 및 Bradyrhizobium elkanii와 98% 이상의 높은 상동성을 나타내었다. 나타내었다.