• Journal of Microbiology and Biotechnology
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• 제19권12호
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• pp.1688-1694
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• 2009

A novel strain of fluorescent pseudomonad (PB-St2) was isolated from surface-sterilized stems of sugarcane grown in Pakistan. The bacterium was identified as Pseudomonas aurantiaca on the basis of 16S rRNA gene sequence analysis and results from physiological and biochemical characteristics carried out with API50 CH and QTS 24 bacterial identification kits. Assays using substrate-specific media for enzymes revealed lipase and protease activities but cellulase, chitinase, or pectinase were not detected. The bacterium was unable to solubilize phosphate or produce indole acetic acid. However, it did produce HCN, siderophores, and homoserine lactones. In dual culture assays on agar, the bacterium showed antifungal activity against an important pathogen of sugarcane in Pakistan, namely Colletotrichum falcatum, as well as for pathogenic isolates of Fusarium oxysporium and F. lateritium but not against F. solani. The antifungal metabolites were identified using thin-layer chromatography, UV spectra, and MALDI-TOFF spectra and shown to be phenazine-1-carboxylic acid (PCA), 2-hydroxyphenazine (2-OH-PHZ), and N-hexanoyl homoserine lactone (HHL) (assessed using only TLC data). The capacity of this bacterium to produce HCN and 2-OH-PHZ, as well as to inhibit the growth of C. falcatum, has not been previously reported.

• 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.

• Journal of Microbiology and Biotechnology
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• 제20권12호
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• pp.1614-1623
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• 2010

Bacteria were isolated from roots of sugarcane varieties grown in the fields of Punjab. They were identified by using API20E/NE bacterial identification kits and from sequences of 16S rRNA and amplicons of the cpn60 gene. The majority of bacteria were found to belong to the genera of Enterobacter, Pseudomonas, and Klebsiella, but members of genera Azospirillum, Rhizobium, Rahnella, Delftia, Caulobacter, Pannonibacter, Xanthomonas, and Stenotrophomonas were also found. The community, however, was dominated by members of the Pseudomonadaceae and Enterobacteriaceae, as representatives of these genera were found in samples from every variety and location examined. All isolates were tested for the presence of five enzymes and seven factors known to be associated with plant growth promotion. Ten isolates showed lipase activity and eight were positive for protease activity. Cellulase, chitinase, and pectinase were not detected in any strain. Nine strains showed nitrogen fixing ability (acetylene reduction assay) and 26 were capable of solubilizing phosphate. In the presence of 100 mg/l tryptophan, all strains except one produced indole acetic acid in the growth medium. All isolates were positive for ACC deaminase activity. Six strains produced homoserine lactones and three produced HCN and hexamate type siderophores. One isolate was capable of inhibiting the growth of 24 pathogenic fungal strains of Colletotrichum, Fusarium, Pythium, and Rhizoctonia spp. In tests of their abilities to grow under a range of temperature, pH, and NaCl concentrations, all isolates grew well on plates with 3% NaCl and most of them grew well at 4 to $41^{\circ}C$ and at pH 11.

• The Plant Pathology Journal
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• 제35권5호
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• pp.425-436
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• 2019

Botrytis cinerea, a major phytopathogenic fungus, has been reported to infect more than 200 crop species worldwide, and it causes massive losses in yield. The aim of this study was to evaluate the inhibitory abilities and effects of Bacillus amyloliquefaciens RS-25, Bacillus licheniformis MG-4, Bacillus subtilis Z-14, and Bacillus subtilis Pnf-4 and their culture filtrates and extracts against the gray mold caused by B. cinerea on postharvest tomato, strawberry, and grapefruit. The results revealed that the cells of Z-14, culture filtrate of RS-25, and cells of Z-14 showed the strongest biocontrol activity against the gray mold on the strawberry, grape, and tomato fruit, respectively. All the strains produced volatile organic compounds (VOCs), and the VOCs of Pnf-4 displayed the highest inhibition values. Based on headspace solid-phase microextraction in combination with gas chromatography-mass spectrometry, esters accounted for the largest percentage of the VOCs produced by RS-25, MG-4, Z-14, and Pnf-4 (36.80%, 29.58%, 30.78%, and 36.26%, respectively). All the strains showed potent cellulase and protease activities, but no chitinase activity. RS-25, Z-14, and MG-4, but not Pnf-4, grew on chrome azurol S agar, and an orange halo was formed around the colonies. All the strains showed biofilm formation, fruit colonization, and lipopeptide production, which may be the main modes of action of the antagonists against B. cinerea on the fruit. This study provides the basis for developing natural biocontrol agents against the gray mold caused by B. cinerea on postharvest fruit.

• 한국토양비료학회지
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• 제43권5호
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• pp.659-666
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• 2010

선행연구에서 근권 토양으로부터 분리된 Lysobacter antibioticus HS124 (HS124)는 lytic enzyme으로써 chitinase, gelatinase, lipase 및 protease 등의 효소와 항생물질인 4-hydroxyphenylacetic acid (4-HPAA)를 생성하였다. 본 실험에서는 HS124를 이용하여 배추좀나방 (diamondback moth, Plutella xylostella L.) 3~4령 유충의 살충활성을 검정하였다. HS124 배양액을 배추좀나방 유충에 처리하였을 때 유충은 파괴되어 분해되었다. HS124가 생성하는 4-HPAA를 유충에 처리하였을 때 처리 농도가 높을수록 살충율은 증가하였으며, HS124 배양액에 Tween 80을 첨가하였을 때 첨가하지 않은 처리구보다 살충율이 1.4배 높았다. 한편 화학 살충제 (IS), HS124 배양액 (HS124), 식물추출물 (매직파이; MP), HS124 배양액+식물추출물 (HS124+MP) 및 멸균수 (SDW)를 이용하여 배추좀나방 유충의 살충율을 검정하였다. HS124+MP 처리구에서 가장 높은 살충율을 나타내었고, IS, MP, HS124 및 SDW 처리구 순으로 살충율이 감소하였다. HS124 처리구는 대조구인 멸균수처리구보다 31% 높은 살충율을 나타내었고, HS124+MP처리구 보다 40% 낮은 살충율을 나타내었다. 이러한 결과로 보아 항생물질과 다양한 lytic enzyme을 생성하는 L. antibioticus HS124 배양액과 식물추출물의 혼합제제는 배추좀나방의 생물학적 방제제로써 가치가있다고 사료된다.

• 한국토양비료학회지
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• 제45권6호
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• pp.1126-1135
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• 2012

다양한 기능을 가진 토착미생물을 분리 동정 후 퇴비화에 적용하여 우수한 기능성을 가진 발효퇴비를 제조하고자 하였다. 7개의 우수 토착미생물을 주축으로 3개의 발효퇴비를 제조하여 생리활성을 조사한 결과, 대두의 발아율 증가, 섬유소, 키틴, 단백질 분해 등의 생리활성이 대조구보다 뛰어나고, 오옥신 생산량이 유의적으로 증가하였다. 퇴비중 암모니아 가스와 휘발성 지방산 함량 역시 2차 발효가 시작되는 20일까지 함량 감소가 있었고, 대두의 건물수량이 증가함을 확인하였다. 또한 식물보호제 분해시험에서도 유의적인 분해율이 있었고, 중금속 함량 역시 유의적으로 감소하였다. 따라서 토착미생물의 다 기능적 활성을 활용한 발효퇴비의 제조는 기존보다 더 향상된 발효퇴비를 농업생산 환경에 적용할 수 있을 것이다.

• Journal of Microbiology and Biotechnology
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• 제30권4호
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• pp.571-582
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• 2020

Quorum sensing (QS)-mediated infections cause severe diseases in human beings. The control of infectious diseases by inhibiting QS using antipathogenic drugs is a promising approach as antibiotics are proving inefficient in treating these diseases. Marine fungal (Pestalotiopsis sydowiana PPR) extract was found to possess effective antipathogenic characteristics. The minimum inhibitory concentration (MIC) of the fungal extract against test pathogen Pseudomonas aeruginosa PAO1 was 1,000 ㎍/ml. Sub-MIC concentrations (250 and 500 ㎍/ml) of fungal extract reduced QS-regulated virulence phenotypes such as the production of pyocyanin, chitinase, protease, elastase, and staphylolytic activity in P. aeruginosa PAO1 by 84.15%, 73.15%, 67.37%, 62.37%, and 33.65%, respectively. Moreover, it also reduced the production of exopolysaccharides (74.99%), rhamnolipids (68.01%), and alginate (54.98%), and inhibited the biofilm formation of the bacteria by 90.54%. In silico analysis revealed that the metabolite of P. sydowiana PPR binds to the bacterial QS receptor proteins (LasR and RhlR) similar to their respective natural signaling molecules. Cyclo(-Leu-Pro) (CLP) and 4-Hydroxyphenylacetamide (4-HPA) were identified as potent bioactive compounds among the metabolites of P. sydowiana PPR using in silico approaches. The MIC values of CLP and 4-HPA against P. aeruginosa PAO1 were determined as 250 and 125 ㎍/ml, respectively. All the antivirulence assays were conducted at sub-MIC concentrations of CLP (125 ㎍/ml) and 4-HPA (62.5 ㎍/ml), which resulted in marked reduction in all the investigated virulence factors. This was further supported by gene expression studies. The findings suggest that the metabolites of P. sydowiana PPR can be employed as promising QS inhibitors that target pathogenic bacteria.

• The Plant Pathology Journal
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• 제34권6호
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• pp.555-566
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• 2018

Two rhizobacteria Bacillus aryabhattai H26-2 and B. siamensis H30-3 were evaluated whether they are involved in stress tolerance against drought and high temperature as well as fungal infections in Chinese cabbage plants. Chinese cabbage seedlings cv. Ryeokgwang (spring cultivar) has shown better growth compared to cv. Buram-3-ho (autumn cultivar) under high temperature conditions in a greenhouse, whilst there was no difference in drought stress tolerance of the two cultivars. In vitro growth of B. aryabhattai H26-2 and B. siamensis H30-3 were differentially regulated under PEG 6000-induced drought stress at different growing temperatures (30, 40 and $50^{\circ}C$). Pretreatment with B. aryabhattai H26-2 and B. siamensis H30-3 enhanced the tolerance of Chinese cabbage seedlings to high temperature, but not to drought stress. It turns out that only B. siamensis H30-3 showed in vitro antifungal activities and in planta crop protection against two fungal pathogens Alternaria brassicicola and Colletotrichum higginsianum causing black spots and anthracnose on Chinese cabbage plants cv. Ryeokgwang, respectively. B. siamensis H30-3 brings several genes involved in production of cyclic lipopeptides in its genome and secreted hydrolytic enzymes like chitinase, protease and cellulase. B. siamensis H30-3 was found to produce siderophore, a high affinity iron-chelating compound. Expressions of BrChi1 and BrGST1 genes were up-regulated in Chinese cabbage leaves by B. siamensis H30-3. These findings suggest that integration of B. aryabhattai H26-2 and B. siamensis H30-3 in Chinese cabbage production system may increase productivity through improved plant growth under high temperature and crop protection against fungal pathogens.

• 미생물학회지
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• 제49권1호
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• pp.64-70
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• 2013

온실가루이(Trialeurodes vaporariorum)는 온실에서의 경제적 주요 해충으로, 직접적으로는 작물을 흡즙 가해하여 영양분고갈로 작물을 고사시키고 간접적으로는 많은 식물바이러스를 매개한다. 이러한 온실가루이를 방제하기 위해 최근에 다양한 합성 농약을 사용하고 있지만, 농약의 오남용으로 인해 온실가루이 개체의 저항성이 높아지고 환경오염을 초래하는 문제가 있다. 그리하여 본 연구에서는 이러한 문제를 극복하고자 온실가루이 사충으로부터 분리된 곤충병원성 곰팡이의 생물학적 특성과 살충성을 조사하였다. 분리된 곤충병원성 곰팡이는 형태학적 조사와 ITS, ${\beta}$-tubulin, EF1-${\alpha}$ 영역의 염기서열을 이용한 분자생물학적 동정을 통하여 Isaria fumosorosea로 동정하였고, I. fumosorosea SDTv로 명명하였다. 그리고 I. fumosorosea SDTv의 온실가루이 약충에 대한 살충력과 포자의 고온, UV-B 안정성, 저온발아력에 대하여 조사 하였다. 살충력 검정은 실험실 조건에서 온실가루이 약충에 대하여 다양한 포자 농도($1{\times}10^5$ - $10^8$ conidia/ml)로 접종한 결과, 7일차에서 84-100%의 살충력을 보였으며 포자 농도가 증가할수록 살충력도 증가하는 양상을 나타내었다. 분리 균주의 포자는 $35^{\circ}C$에서 그리고 0.1 $J/cm^2$ UV-B 조사에 대하여 비교적 안정적이었으며, $4^{\circ}C$ 조건에서 8일차부터 발아하였다. 또한, I. fumosorosea SDTv의 배지에 따른 chitinases와 proteases의 생산 활성을 비교한 결과 배지에 따라 다른 효소 생산 양상을 보였다. 이상의 결과로 온실가루이에 대하여 높은 살충력을 보인 I. fumosorosea SDTv는 온실가루이에 대한 종합적 해충 방제 방법에 있어 효과적인 방제수단의 일환이 될 수 있을 것으로 기대된다.

• 한국토양비료학회지
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• 제44권6호
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• pp.1150-1157
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• 2011

친환경 뿌리혹선충 방제제로써의 활용을 위해 전남 무안 해안가 토양으로부터 chitin 및 gelatin 분해활성이 있는 Streptomyces sampsonii KK1024를 분리하였다. KK1024는 키틴분해효소, 단백질분해효소, 젤라틴분해효소 및 지질분해효소 활성이 있음이 조사되었다. KK1024의 뿌리혹선충 유충 치사 및 알 부화 억제 효과를 조사한 결과, 배양액 50% 처리 시 유충 치사율이 3일째 81%, 알 부화율이 5일째 2%로 나타났다. 또한, 조효소 $183.7{\mu}g\;mL^{-1}$ 처리 시 유충 치사율이 3일째 96%, 알 부화율이 5일째 5%를 나타냈다. 부탄올 추출물질 1% 처리 시 3일째 유충 치사율이 90%, 알 부화율이 0%로 나타났다. 미생물 배양액이 선충 피해 방제와 식물생장에 미치는 영향을 조사해 본 결과, 식물 지상부 무게 및 크기에서 미생물 배양액 처리구가 배지, 비료, 농약처리구 보다 높게 나타났다. 선충 피해 방제에 있어서 미생물 배양액 처리구가 난낭 수, 뿌리혹 수, 토양 내 유충 수에서 농약 처리구 보다는 높게 나타났지만, 배지 및 비료 처리구 보다는 낮게 나타났다. 이러한 결과로 보아 다양한 분해효소 및 살선충 물질을 생성하는 Streptomyces sampsonii KK1024는 뿌리혹선충을 생물학적으로 방제할 수 있는 방제제로서 가치가 있다고 사료된다.