• Journal of Microbiology and Biotechnology
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• 제30권1호
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• pp.118-126
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• 2020

Silicon and phosphorus are elements that are beneficial for plant growth. Despite the abundant availability of silicate and phosphate in the Earth's crust, crop nutritional requirements for silicon and phosphorus are normally met through the application of fertilizer. However, fertilizers are one of the major causes of heavy metal pollution. In our study, we aimed to assess silicate and phosphate solubilization by the bacteria Enterobacter ludwigii GAK2, in the presence and absence of phosphate [Ca₃(PO₄)₂] or silicate (Mg₂O₈Si₃), to counteract cadmium stress in rice (Oryza sativa L). Our results showed that the GAK2-treated rice plants, grown in soil amended with phosphate [Ca₃(PO₄)₂] or silicate (Mg₂O₈Si₃), had significantly reduced cadmium content, and enhanced plant growth promoting characteristics including fresh shoot and root weight, plant height, and chlorophyll content. These plants showed significant downregulation of the cadmium transporter gene, OsHMA2, and upregulation of the silicon carrier gene, OsLsi1. Moreover, jasmonic acid levels were significantly reduced in the GAK2-inoculated plants, and this was further supported by the downregulation of the jasmonic acid related gene, OsJAZ1. These results indicate that Enterobacter ludwigii GAK2 can be used as a silicon and phosphorus bio-fertilizer, which solubilizes insoluble silicate and phosphate, and mitigates heavy metal toxicity in crops.

• 한국미생물·생명공학회지
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• 제34권2호
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• pp.94-100
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• 2006

식물생장 촉진 호르몬인 auxin을 생산하는 균주를 선발하기 위해 경산지역 경작지 토양에서 29종의 세균을 분리하였으며 Salkowsky test를 통해 auxin을 생산하는 14종을 선발하였다. 이 중 CAS(chrome azurol S) blue agar에서 siderophore의 생산을 확인 후 auxin과 siderohroe를 동시에 생산하는 AH18을 최종 선발하였다. AH18의 mung-bean adventitious root induction test를 통해 식물생장 촉진 능이 대조구에 비해 1.5배나 뛰어남을 알 수 있었고, 토마토 pot test에서 토마토 시들음병의 윈인균인 F. oxysporum에 대해서 길항력도 나타내었다. 선발된 AHl8 균주는 16S rDNA와 Biolog system을 통해 Bacillus subtilis 동정되었다. B. subtilis AH18은 Sucrose-asparagine-MgsO$_4$(SAM) medium (pH 6.0)에 접종하여 30$^{\circ}C$에서 3일간 배양 시 siderophore를 가장 많이 생산하는 것을 알 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제26권3호
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• pp.549-557
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• 2016

Aphids are a large group of hemipteran pests that affect the physiology, growth, and development of plants by using piercing mouthparts to consume fluids from the host. Based an recent data, aphids modulate the microbiomes of plants and thereby affect the overall outcome of the biological interaction. However, in a few reports, aboveground aphids manipulate the metabolism of the host and facilitate infestations by rhizosphere bacteria (rhizobacteria). In this study, we evaluated whether aphids alter the plant resistance that is mediated by the bacterial community of the root system. The rhizobacteria were affected by aphid infestation of pepper, and a large population of gram-positive bacteria was detected. Notably, Paenibacillus spp. were the unique gram-positive bacteria to respond to changes induced by the aphids. Paenibacillus polymyxa E681 was used as a rhizobacterium model to assess the recruitment of bacteria to the rhizosphere by the phloem-sucking of aphids and to test the effect of P. polymyxa on the susceptibility of plants to aphids. The root exudates secreted from peppers infested with aphids increased the growth rate of P. polymyxa E681. The application of P. polymyxa E681 to pepper roots promoted the colonization of aphids within 2 days of inoculation. Collectively, our results suggest that aphid infestation modulated the root exudation, which led to the recruitment of rhizobacteria that manipulated the resistance of peppers to aphids. In this study, new information is provided on how the infestation of insects is facilitated through insect-derived modulation of plant resistance with the attraction of gram-positive rhizobacteria.

• 한국미생물·생명공학회지
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• 제39권2호
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• pp.182-187
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• 2011

습지의 갈대토양으로부터 중금속에 내성이 있는 세균이 분리되었다. 분리된 균주는 16S rDNA 염기서열분석에 의거하여 Alcaligenes sp.로 동정되었다. 납, 크롬, 카드뮴, 아연 및 구리와 같은 중금속을 배지에 첨가하였다. 분리균주 Alcaligenes sp. KC-1을 구리가 0 mM에서 20 mM의 농도로 첨가된 배지에서 배양하였을 때 균주의 생장에 미치는 독성을 알아보았다. 분리균주는 구리가 존재할 때 42시간 배양된 후 7.34 mM의 $EC_{50}$값과 $OD_{600\;nm}$에서 0.83의 흡광도 값을 보여주는 구리 내성균주였다.

• Journal of Microbiology and Biotechnology
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• 제30권10호
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• pp.1500-1509
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• 2020

Drought is a major abiotic factor and has drastically reduced crop yield globally, thus damaging the agricultural industry. Drought stress decreases crop productivity by negatively affecting crop morphological, physiological, and biochemical factors. The use of drought tolerant bacteria improves agricultural productivity by counteracting the negative effects of drought stress on crops. In this study, we isolated bacteria from the rhizosphere of broccoli field located in Daehaw-myeon, Republic of Korea. Sixty bacterial isolates were screened for their growth-promoting capacity, in vitro abscisic acid (ABA), and sugar production activities. Among these, bacterial isolates YNA59 was selected based on their plant growth-promoting bacteria traits, ABA, and sugar production activities. Isolate YNA59 highly tolerated oxidative stress, including hydrogen peroxide (H₂O₂) and produces superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities in the culture broth. YNA59 treatment on broccoli significantly enhanced plant growth attributes, chlorophyll content, and moisture content under drought stress conditions. Under drought stress, the endogenous levels of ABA, jasmonic acid (JA), and salicylic acid (SA) increased; however, inoculation of YNA59 markedly reduced ABA (877 ± 22 ng/g) and JA (169.36 ± 20.74 ng/g) content, while it enhanced SA levels (176.55 ± 9.58 ng/g). Antioxidant analysis showed that the bacterial isolate YNA59 inoculated into broccoli plants contained significantly higher levels of SOD, CAT, and APX, with a decrease in GPX levels. The bacterial isolate YNA59 was therefore identified as Variovorax sp. YNA59. Our current findings suggest that newly isolated drought tolerant rhizospheric Variovorax sp. YNA59 is a useful stress-evading rhizobacterium that improved drought-stress tolerance of broccoli and could be used as a bio-fertilizer under drought conditions.

• 한국자원식물학회지
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• 제20권2호
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• pp.216-219
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• 2007

Root colonization by a rhizobacterium, Pseudomonas chlororaphis O6, elicited induced systemic resistance (ISR) in the leaves of cucumber plants against fungal and bacterial pathogens. To understand the role of unique genes during strain O6-mediated ISR, a suppressive subtractive hybridization method was undertaken and led to isolation of twenty-five distinct genes. The transcriptional levels of all the genes showed an increase much earlier under O6 treatment than in water control plants only after challenge with pathogen, while no difference detected on the plants without pathogen challenge. This suggests that O6-mediated ISR is associated with the priming phenomenon, an enhanced capacity for the rapid and effective activation of cellular defense responses after challenge inoculation.

• 식물병연구
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• 제22권4호
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• pp.284-288
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• 2016

식물 생장촉진근권세균 B. vallismortis BS07M을 점토로 제형화한 제제(CP)는 고추의 생육촉진 및 병저항성 유도 효과를 보였다. CP를 육묘 상토에 혼합하는 것은 기존의 세균 현탁액을 유묘 또는 포장에서 재배 중에 관주 살포하는 방법에 비해 비교적 사용하기 쉽고, 그 효과가 포장에서도 지속됨으로써 고추의 열매 개당 무게를 증가시켰으며, 수확 후 저장 중에 자연적으로 발생하는 무름 증상을 감소시킴으로써 보관기간을 늘리는 효과가 있을 것이다.

• 생명과학회지
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• 제13권5호
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• pp.582-589
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• 2003

본 연구에서는 가지과 작물의 근권에서 유용한 균주를 분리하고 근권ㆍ길항ㆍ생육촉진미생물을 선별ㆍ제제화하고 상토에 첨가하여 미생물제제 혼입 상토를 제조한 후 고추 플러그묘의 초기 생장에 미치는 영향을 조사하였다. 근권미생물로는 가지과 작물의 뿌리 및 재배 토양 등 385점의 균원시료로부터 540여점을 분리한 후, 가지과 작물에 공통적으로 발생되는 Alternaria solani, Botrytis cinerea, Fusarium oxysporium, Phytophthora capsici, Sclerotinia sclerotiorum 등의 병원균에 높은 길항력을 가진 미생물 20여종을 선발하고, 이들 길항미생물 중에서 고추의 초기 생육을 촉진시키는 MJ-3균주를 최종 선발하였다. 근권ㆍ길항ㆍ생육촉진미생물인 분리주 MJ-3은 Bergey's manual of systematic bacteriology의 방법과 16S rDNA sequence법 등으로 조사하여 Bacillus amyloliquefaciens동정하였다. 제제화한 B. amyloliquefaciens를 상토에 첨하여 미생물 혼입 상토를 제조하였고, 이를 이용하여 재배한 고추 플러그 묘는 초장과 경경, 뿌리길이, 생체중량 등이 모두 대조구에 비해 소량 증가되었으나, 특히 뿌리의 생체중량이 대조구가 0.61g/plant인데 비해 시험구는 0.88g/plant로 44.3% 증가하였다. 미생물제제 첨가 상토에서 재배한 고추의 gib-berellin (GA$_1$) 함량은 0.559ng/g(건조중량)이었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제16권5호
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• pp.9-17
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• 2011

Positive effect of multiple-PGPR (Plan Growth Promoting Rhizobacteria), isolated from heavy metal contaminated soil, on the germination of Barnyard grass (Echinochloa crus-galli var. frumentacea) was quantitatively estimated in 5 heavy metal (Cd, As, Ni, Cu, and Pb) contaminated liquid medium. The $EC_{50}$ value for respective heavy metal was estimated by TSK (Trimmed Speraman-Karber) model based on germination rate. The results showed overall increase in $EC_{50}$ with PGPR inoculation. The $EC_{50}$ value increased 1.4% from 96.0 mg/L (control) to 97.4 mg/L (PGPR-treated) in As contaminated medium. In Ni contaminated medium, the $EC_{50}$ value increased 31.9% from 148.0 mg/L (control) to 195.2 mg/L (PGPR-treated), while the $EC_{50}$ showed 4.8% increase from 63.4 mg/L (control) to 66.5 mg/L (PGPR-treated) in Cu medium. Overall seedling growth was stronger in the PGPR treated seeds than that in the control, but positive effect on seedling growth was not conspicuous. At effective concentration of 100 mg/L, the average seedling length of the PGPR treatment in As, Cd, Cu, and Ni medium, respectively, was 1.13, 0.14, 0.40, and 0.06 cm longer than that in the control. However, the increase of seedling growth was statistically insignificant (p < 0.05). These results suggest that inoculation of the isolated-PGPR exerts positive effects on seed germination by reducing heavy metal toxicity and can be an effective tool for application of phytoremediation on heavy metal contaminated soils.

• Journal of Microbiology and Biotechnology
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• 제20권11호
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• pp.1491-1499
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• 2010

Rhizosphere microorganisms possessing phytase activity are considered important for rendering phytate-phosphorus (P) available to plants. In the present study, the Citrobacter braakii phytase gene (appA) was overexpressed in rhizobacteria possessing plant growth promoting (PGP) traits, for increasing their potential as bioinoculants. AppA was cloned under the lac promoter in the broadhost-range expression vector pBBR1MCS-2. Transformation of the recombinant construct pCBappA resulted in high constitutive phytase activity in all of the eight rhizobacterial strains belonging to genera Pantoea, Citrobacter, Enterobacter, Pseudomonas (two strains), Rhizobium (two strains), and Ensifer that were studied. Transgenic rhizobacterial strains were found to display varying levels of phytase activity, ranging from 10-folds to 538-folds higher than the corresponding control strains. The transgenic derivative of Pseudomonas fluorescens CHA0, a well-characterized plant growth promoting rhizobacterium, showed the highest expression of phytase (~8 U/mg) activity in crude extracts. Although all transformants showed high phytase activity, rhizobacteria having the ability to secrete organic acid showed significantly higher release of P from Ca-phytate in buffered minimal media. AppA overexpressing rhizobacteria showed increased P content, and dry weight (shoot) or shoot/ root ratio of mung bean (Vigna radiata) plants, to different extents, when grown in semisolid agar (SSA) medium containing Na-phytate or Ca-phytate as the P sources. This is the first report of the overexpression of phytase in rhizobacterial strains and its exploitation for plant growth enhancement.