• Journal of Microbiology and Biotechnology
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• 제17권1호
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• pp.96-103
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• 2007

Plant growth-promoting rhizobacteria (PGPR) have the potential to be used as microbial inoculants to reduce disease incidence and severity and to increase crop yield. Some of the PGPR have been reported to be able to enter plant tissues and establish endophytic populations. Here, we demonstrated an approach to screen bacterial endophytes that have the capacity to promote the growth of pepper seedlings and protect pepper plants against a bacterial pathogen. Initially, out of 150 bacterial isolates collected from healthy stems of peppers cultivated in the Chungcheong and Gyeongsang provinces of Korea, 23 putative endophytic isolates that were considered to be predominating and representative of each pepper sample were selected. By phenotypic characterization and partial 16S rDNA sequence analysis, the isolates were identified as species of Ochrobacterium, Pantoea, Pseudomonas, Sphingomonas, Janthinobacterium, Ralstonia, Arthrobacter, Clavibacter, Sporosarcina, Acidovorax, and Brevundimonas. Among them, two isolates, PS4 and PS27, were selected because they showed consistent colonizing capacity in pepper stems at the levels of $10^6-10^7CFU/g$ tissue, and were found to be most closely related to Pseudomonas rhodesiae and Pantoea ananatis, respectively, by additional analyses of their entire 16S rDNA sequences. Drenching application of the two strains on the pepper seedlings promoted significant growth of peppers, enhancing their root fresh weight by 73.9% and 41.5%, respectively. The two strains also elicited induced systemic resistance of plants against Xanthomonas axonopodis pv. vesicatoria.

• Journal of Microbiology and Biotechnology
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• 제20권11호
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• pp.1577-1584
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• 2010

In total, 140 halotolerant bacterial strains were isolated from both the soil of barren fields and the rhizosphere of six naturally growing halophytic plants in the vicinity of the Yellow Sea, near the city of Incheon in the Republic of Korea. All of these strains were characterized for multiple plant growth promoting traits, such as the production of indole acetic acid (IAA), nitrogen fixation, phosphorus (P) and zinc (Zn) solubilization, thiosulfate ($S_2O_3$) oxidation, the production of ammonia ($NH_3$), and the production of extracellular hydrolytic enzymes such as protease, chitinase, pectinase, cellulase, and lipase under in vitro conditions. From the original 140 strains tested, on the basis of the latter tests for plant growth promotional activity, 36 were selected for further examination. These 36 halotolerant bacterial strains were then tested for 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. Twenty-five of these were found to be positive, and to be exhibiting significantly varying levels of activity. 16S rRNA gene sequencing analyses of the 36 halotolerant strains showed that they belong to 10 different bacterial genera: Bacillus, Brevibacterium, Planococcus, Zhihengliuella, Halomonas, Exiguobacterium, Oceanimonas, Corynebacterium, Arthrobacter, and Micrococcus. Inoculation of the 14 halotolerant bacterial strains to ameliorate salt stress (150 mM NaCl) in canola plants produced an increase in root length of between 5.2% and 47.8%, and dry weight of between 16.2% and 43%, in comparison with the uninoculated positive controls. In particular, three of the bacteria, Brevibacterium epidermidis RS15, Micrococcus yunnanensis RS222, and Bacillus aryabhattai RS341, all showed more than 40% increase in root elongation and dry weight when compared with uninoculated salt-stressed canola seedlings. These results indicate that certain halotolerant bacteria, isolated from coastal soils, have a real potential to enhance plant growth under saline stress, through the reduction of ethylene production via ACC deaminase activity.

• 미생물학회지
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• 제50권4호
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• pp.368-371
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• 2014

염 스트레스를 비롯한 다양한 비생물학적 스트레스는 식물의 생장저해와 작물 생산량을 감소시키는 요인으로 작용한다. 계화도 간척지 토양에서 식물생장 촉진 세균을 분리하여 Pseudomonas sp. G19로 명명하였다. G19 균주는 36시간 배양 후 $7.5{\mu}g/ml$의 indole acetic acid를 생산하고 불용성인산을 25% 가용화시켰으며, 식물의 에틸렌 감소와 관련된 1-aminocyclopropane-1-carboxylate deaminase를 발현하였다. 또한 150 mM NaCl에 침지된 염 조건의 토양에서 재배된 유묘기 배추를 이용한 실증실험에서 G19 균주는 배추의 생체중량을 증가시킴으로써 염 스트레스의 경감 및 생장 촉진에 관여함을 알 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제16권10호
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• pp.1622-1628
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• 2006

Bacteria from the Methylobacterium genus, called pink-pigmented facultative methylotrophic bacteria (PPFMs), are common inhabitants of plants, potentially dominating the phyllosphere population, and are also encountered in the rhizosphere, seeds, and other parts of plants, being versatile in nature. The consistent success of the Methylobacterium plant association relies on methylotrophy, the ability to utilize the one-carbon compound methanol emitted by plants. However, the efficiency of Methylobacterium in plant growth promotion could be better exploited and thus has attracted increasing interest in recent years. Accordingly, the present study investigated the inoculation effects of Methylobacterium sp. strains CBMB20 and CBMB 110 on seed imbibition to tomato and red pepper on the growth and accumulation of phytohormone levels under gnotobiotic conditions. Seeds treated with the Methylobacterium strains showed a significant increase in root length when compared with either the uninoculated control or Methylobacterium extorquens $miaA^-$ knockout mutanttreated seeds. Extracts of the plant samples were used for indole-3-acetic acid (IAA), trans-zeatin riboside (t-ZR), and dihydrozeatin riboside (DHZR) assays by immunoanalysis. The treatment with Methylobacterium sp. CBMB20 or CBMB 110 produced significant increases in the accumulation of IAA and the cytokinins t-ZR and DHZR in the red pepper extracts, whereas no IAA was detected in the tomato extracts, although the cytokinin concentrations were significantly increased. Therefore, this study proved that the versatility of Methylobacterium as a plant-growth promoting bacteria could be better exploited.

• Journal of Microbiology and Biotechnology
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• 제25권9호
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• pp.1467-1475
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• 2015

The use of microbial extracts containing plant hormones is a promising technique to improve crop growth. Little is known about the effect of bacterial cell-free extracts on plant growth promotion. This study, based on phytohormonal analyses, aimed at exploring the potential mechanisms by which Enterococcus faecium LKE12 enhances plant growth in oriental melon. A bacterial strain, LKE12, was isolated from soil, and further identified as E. faecium by 16S rDNA sequencing and phylogenetic analysis. The plant growth-promoting ability of an LKE12 bacterial culture was tested in a gibberellin (GA)-deficient rice dwarf mutant (waito-C) and a normal GA biosynthesis rice cultivar (Hwayongbyeo). E. faecium LKE12 significantly improved the length and biomass of rice shoots in both normal and dwarf cultivars through the secretion of an array of gibberellins (GA₁, GA₃, GA₇, GA₈, GA₉, GA₁₂, GA₁₉, GA₂₀, GA₂₄, and GA₅₃), as well as indole-3-acetic acid (IAA). To the best of our knowledge, this is the first study indicating that E. faecium can produce GAs. Increases in shoot and root lengths, plant fresh weight, and chlorophyll content promoted by E. faecium LKE12 and its cell-free extract inoculated in oriental melon plants revealed a favorable interaction of E. faecium LKE12 with plants. Higher plant growth rates and nutrient contents of magnesium, calcium, sodium, iron, manganese, silicon, zinc, and nitrogen were found in cell-free extract-treated plants than in control plants. The results of the current study suggest that E. faecium LKE12 promotes plant growth by producing GAs and IAA; interestingly, the exogenous application of its cell-free culture extract can be a potential strategy to accelerate plant growth.

• Journal of Microbiology and Biotechnology
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• 제25권6호
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• pp.903-909
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• 2015

Indole-3-acetic acid (IAA) production is a typical mechanism of plant growth promotion by some rhizobacteria. However, a functional genomic study is necessary to unravel the function and mechanism of IAA signaling during rhizobacteria-plant interactions. In this study, the expression of SlIAA1 and SlIAA9 among the auxin response genes in tomato was examined during the interaction between IAA-producing Acinetobacter guillouiae SW5 and tomato plants. When 3-day grown tomato seedlings were treated for 30 min with 10~100 µM of IAA produced by bacteria from tryptophan, the relative mRNA levels of SlIAA1 and SlIAA9 increased significantly compared with those of the control, demonstrating that IAA produced by this bacterium can induce the expressions of both genes. Inoculation of live A. guillouiae SW5 to tomato seedlings also increased the expressions of SlIAA1 and SlIAA9, with more mRNA produced at higher bacterial density. In contrast, treatment of tomato seedlings with dead A. guillouiae SW5 did not significantly affect the expression of SlIAA1and SlIAA9. When 3-day bacterial culture in tomato root exudates was administered to tomato seedlings, the relative mRNA level of SlIAA1 increased. This result indicated that the plant may take up IAA produced by bacteria in plant root exudates, which may increase the expression of the auxin response genes, with resulting promotion of plant growth.

• Journal of Plant Biotechnology
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• 제47권4호
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• pp.337-344
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• 2020

식물생장촉진 미생물은 식물 뿌리에 영양을 원활하게 공급하거나 휘발성 유기화합물(Volatile Organic Compound, VOC)를 이용하여 식물의 내재 인자와 상호작용을 통해 생장을 촉진한다. 본 연구에서는 식물 생장 촉진 진균 UOS의 담배에서의 생장 촉진 효과를 평가하고, 계통발생학적 분석을 통해 동정하였다. 또한, UOS의 식물 생장 촉진 인자를 탐색하고자 Gas Chromatography-Mass Spectrometry (GC-MS) 분석을 통해 UOS의 VOCs를 확인하였다. UOS를 처리한 담배는 무처리구에 비해서 3.8배의 생중량이 증가하였고, I-plate를 이용한 분리된 공간에서는 UOS처리구가 무처리에 비해 생중량이 4.2배 증가하였다. 또한, UOS 처리구의 식물은 주근의 길이가 약2배 짧아지고 측근의 수가 약2배 증가하였다. UOS은 포자 및 균사 형태와 Internal transcribed spacer (ITS) 유전자 염기서열을 통하여 Phoma sp.으로 동정되었으며, 이들은 GC-MS분석을 통해 UOS는 hexamethylcyclotrisiloxane (D3)라는 VOC를 갖고 있는 것이 밝혀졌다. 이 결과들은 Phoma sp.의 진균 UOS가 VOC물질인 D3을 통해서 간접적으로 식물 생장 촉진 및 뿌리 발달에 영향을 미치는 것을 나타낸다. UOS와 그의 VOC인 D3의 활용은 농업에서 생장량 증대에 기여할 것으로 판단된다.

• Journal of Applied Biological Chemistry
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• 제66권
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• pp.394-403
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• 2023

지속 가능하고 친환경적인 농업 관행을 추구하기 위해 우리는 40년이 넘는 장기간 동안 화학 비료를 사용하지 않은 토양에 서식하는 근권 박테리아에 대한 광범위한 연구를 수행하였다. 이번 조사를 통해 식물생장촉진 근권박테리아 총 80종을 분리하고 이들의 식물생장 증진 가능성을 평가했다. 이러한 분리균중에서 Burkholderia cepacia CD2는 가장 우수한 식물 성장촉진 활성과 생장능을 나타내어 추가 분석을 위한 최적의 후보균주로 선정되었다. Burkholderia cepacia CD2는 인 가용화 능력, 사이드로포어 생산, 탈질화 능력, 아질산 이온 활용능력 및 요소분해효소 활성을 포함하여 식물 성장에 도움이 되는 다양한 유익한 특성을 나타내었다. 이러한 특성은 식물의 성장과 발달에 긍정적인 영향을 미치는 것으로 잘 알려져 있다. 균주의 분류학적 분류를 검증하기 위해 16S rRNA 유전자 서열분석을 통해 Burkholderia 속 내 위치를 확인하여 계통발생 관계에 대한 추가 통찰력을 제공하였다. 식물 생장 촉진 특성의 기본 메커니즘을 더 깊이 조사하기 위해 우리는 CD2에서 식물 생장촉진과 관련된 특정 유전자의 존재를 확인하려고 하였다. 이를 달성하기 위해 옥스포드 나노포어를 활용하여 전장 유전체 시퀀싱을 수행하였다. CD2 게놈에 대한 전장유전체 분석을 통해 식물 생장 개선에 중추적 요인으로 생각되는 하위 시스템 기능을 확인하였다. 이러한 발견을 바탕으로 Burkholderia cepacia CD2는 미생물 비료로 작용하여 화학 비료에 대한 지속 가능한 대안을 제공할 수 있는 잠재력을 가지고 있다는 결론을 내릴수 있다.

• 한국환경농학회지
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• 제39권1호
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• pp.20-25
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• 2020

BACKGROUND: Marine algae is a productive organism that is consumed as a nutritious food. However, large amounts of unused portions of the algae are incinerated as trash or dumped in the sea, causing pollution. Recycling algae is important for saving resources and conserving the environment. In this study, the fucoidan which is a major carbohydrate of marine algae was tested as a source of fertilizer for farming. METHODS AND RESULTS: The growth rate of the melon was examined after treating fucoidan and the melon growth factors, weight and length of stem were measured. To discover the mechanism of melon growth promotion of fucoidan, bacteria that decomposed fucoidan were isolated from soil and abalone. Bacillus wiedmannii and Stenotrophomonas pavanii were isolated from terrestrial soil and Pseudomonas sp. was isolated from abalone. Among these three bacteria, Pseudomonas sp. had the highest and most specific fucoidan-decomposing activity. When Pseudomonas sp. was treated with fucoidan on melon-growing soil, the growth of melon was relatively improved compared to the treatment with fucoidan alone. CONCLUSION: We found that fucoidan, the main carbohydrate of marine algae, promoted melon growth. Fucoidan-decomposing microorganisms were isolated from terrestrial soil and marine organism, and we found that these bacteria stimulated the effect of melon growth promotion of marine algae. This is the first report that confirms the fertilizer effect of marine algae and shows the use of bacteria with marine algae.

• Journal of Ginseng Research
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• 제42권3호
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• pp.304-311
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• 2018

Background: Ginseng black spot disease resulting from Alternaria panax Whuetz is a common soil-borne disease, with an annual incidence rate higher than 20-30%. In this study, the bacterial strains with good antagonistic effect against A. panax are screened. Methods: A total of 285 bacterial strains isolated from ginseng rhizosphere soils were screened using the Kirby-Bauer disk diffusion method and the Oxford cup plate assay. We analyzed the antifungal spectrum of SZ-22 by confronting incubation. To evaluate the efficacy of biocontrol against ginseng black spot and for growth promotion by SZ-22, we performed pot experiments in a plastic greenhouse. Taxonomic position of SZ-22 was identified using morphology, physiological, and biochemical characteristics, 16S ribosomal DNA, and gyrB sequences. Results: SZ-22 (which was identified as Brevundimonas terrae) showed the strongest inhibition rate against A. panax, which showed 83.70% inhibition, and it also provided broad-spectrum antifungal effects. The inhibition efficacies of the SZ-22 bacterial suspension against ginseng black spot reached 82.47% inhibition, which is significantly higher than that of the 25% suspension concentrate azoxystrobin fungicide treatment (p < 0.05). Moreover, the SZ-22 bacterial suspension also caused ginseng plant growth promotion as well as root enhancement. Conclusion: Although the results of the outdoor pot-culture method were influenced by the pathogen inoculum density, the cropping history of the field site, and the weather conditions, B. terrae SZ-22 controlled ginseng black spot and promoted ginseng growth successfully. This study provides resource for the biocontrol of ginseng black spot.