• The Plant Pathology Journal
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• 제29권2호
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• pp.125-135
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• 2013

In agro-ecosystems worldwide, some of the most important and devastating diseases are caused by soil-borne necrotrophic fungal pathogens, against which crop plants generally lack genetic resistance. However, plants have evolved approaches to protect themselves against pathogens by stimulating and supporting specific groups of beneficial microorganisms that have the ability to protect either by direct inhibition of the pathogen or by inducing resistance mechanisms in the plant. One of the best examples of protection of plant roots by antagonistic microbes occurs in soils that are suppressive to take-all disease of wheat. Take-all, caused by Gaeumannomyces graminis var. tritici, is the most economically important root disease of wheat worldwide. Take-all decline (TAD) is the spontaneous decline in incidence and severity of disease after a severe outbreak of take-all during continuous wheat or barley monoculture. TAD occurs worldwide, and in the United States and The Netherlands it results from a build-up of populations of 2,4-diacetylphloroglucinol (2,4-DAPG)-producing fluorescent Pseudomonas spp. during wheat monoculture. The antibiotic 2,4-DAPG has a broad spectrum of activity and is especially active against the take-all pathogen. Based on genotype analysis by repetitive sequence-based-PCR analysis and restriction fragment length polymorphism of phlD, a key 2,4-DAPG biosynthesis gene, at least 22 genotypes of 2,4-DAPG producing fluorescent Pseudomonas spp. have been described worldwide. In this review, we provide an overview of G. graminis var. tritici, the take-all disease, Pseudomonas biocontrol agents, and mechanism of disease suppression.

• Journal of Microbiology and Biotechnology
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• 제18권11호
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• pp.1741-1746
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• 2008

This study was conducted to select endophytic actinomycetes as biocontrol agents against Chinese cabbage clubroot caused by Plasmodiophora brassicae. A total of 81 endophytic actinomycetes were isolated from surface-sterilized roots of Chinese cabbage that was grown on paddy field and upland soils collected from various locations in Korea. By using 16S ribosomal DNA (rDNA) gene sequencing, they were classified to 8 actinobacterial genera. The genus Microbispora (67%) was most frequently isolated, followed by Streptomyces (12%) and Micromonospora (11%). Three of the 81 isolates, when inoculated in germinated Chinese cabbage seeds and then transplanted to pots, effectively suppressed the occurrence of a post-inoculated strain of P. brassicae in the pots. They showed control values of 58% for strain A004, 33% for strain A011, and 42% for strain A018. Based on cell wall components, morphological characteristics, and phylogenetic analyses, the three antagonistic isolates were identified as Microbispora rosea subsp. rosea (A004 and A011) and Streptomyces olivochromogenes (A018). Further researches on the field efficacy and action modes of the three actinomycetes are in progress.

• 미생물학회지
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• 제55권2호
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• pp.157-159
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• 2019

낙동강 주변에서 채취한 토양으로부터 분리한 Pseudomonas fluorescens NBC275 (Pf275) 균주는 식물과 곤충에 병을 일으키는 곰팡이류에 우수한 항균력을 보였다. 본 연구에서는 Pf275 균주의 전체염기서열을 해독하고 분석하였는데, 총 염기서열은 6,610,362 bp였고, GC 함량은 60.9%였다. 염색체는 5,869개의 단백질을 암호화하였고, 16개의 rRNA와 65개의 tRNA로 구성되어 있었다. 유전체의 분석을 통해 항균력을 나타내는 2차 대사산물을 암호화하는 유전자를 확인할 수 있었는데, Pf275 균주는 pyoverdine, 2, 4-diacetylphloroglucinol 및 phenazine 등의 항균물질을 생산하였고, 이들 대사산물에 의해 항균력 및 생물방제효과를 나타내는 것으로 판단된다.

• Journal of Microbiology and Biotechnology
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• 제33권1호
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• pp.61-74
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• 2023

The global increase in multidrug-resistant (MDR) bacteria has inspired researchers to develop new strategies to overcome this problem. In this study, 23 morphologically different, soil-isolated actinomycete cultures were screened for their antibacterial ability against MDR isolates of ESKAPE pathogens. Among them, isolate BOGE18 exhibited a broad antibacterial spectrum, so it was selected and identified based on cultural, morphological, physiological, and biochemical characteristics. Chemotaxonomic analysis was also performed together with nucleotide sequencing of the 16S rRNA gene, which showed this strain to have identity with Streptomyces lienomycini. The ethyl acetate extract of the cell-free filtrate (CFF) of strain BOGE18 was evaluated for its antibacterial spectrum, and the minimum inhibitory concentration (MIC) ranged from 62.5 to 250 ㎍/ml. The recorded results from the in vitro anti-biofilm microtiter assay and confocal laser scanning microscopy (CLSM) of sub-MIC concentrations revealed a significant reduction in biofilm formation in a concentration-dependent manner. The extract also displayed significant scavenging activity, reaching 91.61 ± 4.1% and 85.06 ± 3.14% of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), respectively. A promising cytotoxic ability against breast (MCF-7) and hepatocellular (HePG2) cancer cell lines was obtained from the extract with IC₅₀ values of 47.15 ± 13.10 and 122.69 ± 9.12 ㎍/ml, respectively. Moreover, based on gas chromatography-mass spectrometry (GC-MS) analysis, nine known compounds were detected in the BOGE18 extract, suggesting their contribution to the multitude of biological activities recorded in this study. Overall, Streptomyces lienomycini BOGE18-derived extract is a good candidate for use in a natural combating strategy to prevent bacterial infection, especially by MDR pathogens.

• The Plant Pathology Journal
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• 제39권6호
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• pp.600-613
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• 2023

Fusarium oxysporum is the main pathogen causing Fusarium basal rot in onion (Allium cepa L.), which incurs significant yield losses before and after harvest. Among management strategies, biological control is an environmentally safe and sustainable alternative to chemical control. In this study, we isolated and screened bacteria for antifungal activity against the basal rot pathogen F. oxysporum. Isolates 23-045, 23-046, 23-052, 23-055, and 23-056 significantly inhibited F. oxysporum mycelial growth and conidial germination. Isolates 23-045, 23-046, 23-052, and 23-056 suppressed the development of Fusarium basal rot in both onion seedlings and bulbs in pot and spray inoculation assays. Isolate 23-055 was effective in onion seedlings but exhibited weak inhibitory effect on onion bulbs. Based on analyses of the 16S rRNA and rpoB gene sequences together with morphological analysis, isolates 23-045, 23-046, 23-052, and 23-055 were identified as Bacillus thuringiensis, and isolate 23-056 as Bacillus toyonensis. All five bacterial isolates exhibited cellulolytic, proteolytic, and phosphate-solubilizing activity, which may contribute to their antagonistic activity against onion basal rot disease. Taken together B. thuringiensis 23-045, 23-046, 23-052, and 23-055 and B. toyonensis 23-056 have potential for the biological control of Fusarium basal rot in onion.

• 한국토양비료학회지
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• 제39권4호
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• pp.195-203
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• 2006

길항미생물 MP-1은 여러 종의 곰팡이와 효모 및 음식물을 부패시키는 세균 (그람양성 및 음성) 에 대하여 항균활성을 보였다. MP-1의 16S rRNA gene 염기서열은 기존에 밝혀진 Brukholderia sp.의 염기서열과 99-100% 유사하였다. 배양액으로부터의 항균물질은 에틸아세테이트 (EtOAc)를 사용하여 분리하였으며 EtOAc에 용해된 산성 분획은 silica gel, Sephadex LH-20, ODS 컬럼크로마토 그래피 및 HPLC를 사용하여서 정제를 실시 하였다. 최종적으로 Gas chromatographic-mass 스펙트럼을 통한 분석을 통하여 4 종의 항균 활성을 나타내는 물질은 phenylacetic acid, hydrocinnamic acid, 4-hydroxyphenylacetic acid 및 4-hydroxyphenylacetate methyl ester로 확인 되었다. 각각의 항균 활성물질들의 미생물에 대한 최소저해농도(MIC)는 $250{\sim}2500ug\;ml^{-1}$ 인 것으로 나타났다. 또한 6 mm paper disc 에서의 1mg (건물중) 산성 분획의 항균활성은 같은 비율로 혼합한 표준혼합용액 보다 더 효과적인 것으로 나타났다.

• 생명과학회지
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• 제21권10호
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• pp.1428-1433
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• 2011

본 연구에서는 ACE 저해능 및 항산화능이 있는 식물성 젖산균을 다양한 식물체로부터 분리한 후, 그 특성을 조사하였다. 김치, 부추, 포도 및 동동주에서 K-1, K-21, L-5, G-3 및 D-3 균주가 분리되었으며, 16S rRNA gene 염기서열 분석을 통하여 이들은 각각 Pediococcus pentosaceus, Lactobacillus plantarum, Weissella cibaria, L. plantarum 및 L. brevis로 동정되었다. 분리균주들은 MRS broth에서 44.3-71.9%의 ACE 저해능을 나타내었으며, 특히 G-3, L-5, K-1 균주는 skim milk가 함유된 MRS broth에서 59.0-8-98.6%의 높은 ACE 저해능을 나타내었다. 분리 균주는 42.5-82.7%의 DPPH radical 소거능을 나타내었으며, G-3 및 K-1 균주는 pH 2.5의 인공위액에서 42.2-88.1%의 높은 생존율을 나타내었다. 분리균주는 0.3% oxgall에서 24시간 배양시 55.4-112.8%의 내성을 나타내었다. 또한 분리균주는 유기산 생성에 따른 pH 감소 효과로 인하여 Pseudomonas aeruginosa를 포함한 일부 병원성 세균의 생육을 억제할 수 있었다.

• 한국균학회지
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• 제47권4호
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• pp.417-425
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• 2019

다양한 생물적 스트레스로부터 경제적으로 중요한 식물을 보호하기 위한 친환경 biocontrol agents (BCAs)는 오늘날 농업 및 생태 분야에서 다양하게 사용되고 있다. 다양한 BCAs 중에서, 많은 그람 양성Bacillus 속 아종이 친환경 생물학적 살충제 및 비료로서 성공적으로 산업화되었다. 이 연구에서 우리는 식물병원성 균류의 균사생장에 길항 효과를 보여주는 BCAs 중 하나인 Bacillus thuringiensis C25가 흰날개무늬병을 일으키는Rosellinia necatrix에 대한 길항작용이 있음을 확인하였다. 주사전자현미경을 통해B. thuringiensis C25가R. necatrix의 균사 세포벽을 분해하여 균사생장을 억제하는 것을 확인하였다. B. thuringiensis C25의 전장 유전체에서 5,683 유전자 세트의 서열을 동정하였고, 잠재적으로 곰팡이 세포벽 분해 효소 (CWDE)를 암호화하는 유전자 세트를 선발하였다. R. necatrix에 대한 균사성장 억제효과는B. thuringiensis C25의 균사 세포벽 분해 유전자의 전사 활성과 높은 상관 관계가 있었다. 상세하게는, B. thuringiensis C25에서ChiA, B 및 Glycos_transf_2 유전자를 포함하는 CWDE의 전사체 수준은R. necatrix와의 공동 배양에 의해 향상되었다. 결론적으로, 본 연구에서는 B. thuringiensis C25가 R. necatrix를 제어할 수 있는 생물학적 소재가 될 수 있으며, 식물 병원체에 대한 BCA의 항진균성 메커니즘의 이해를 촉진할 수 있음을 제시하였다.

• Journal of Microbiology and Biotechnology
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• 제15권6호
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• pp.1286-1298
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• 2005

The genus Paenibacillus is a new group of bacilli separated from the genus Bacillus, and most of species have been isolated from soil. In the present study, we collected 450 spore-forming bacilli from the roots of winter crops, such as barley, wheat, onion, green onion, and Chinese cabbage, which were cultivated in the southern part of Korea. Among these 450 isolates, 104 Paenibacillus-like isolates were selected, based on their colony shape, odor, color, and endospore morphology, and 41 isolates were then finally identified as Paenibacillus spp. by 16S rDNA sequencing. Among the 41 Paenibacillus isolates, 23 were classified as P. polymyxa, a type species of the genus Paenibacillus, based on comparison of the 16S rDNA sequences with those of 32 type strains of the genus Paenibacillus from the GenBank database. Thirty-five isolates among the 41 Paenibacillus isolates exhibited antagonistic activity towards plant fungal and bacterial pathogens, whereas 24 isolates had a significant growth-enhancing effect on cucumber seedlings, when applied to the seeds. An assessment of the root-colonization capacity under gnotobiotic conditions revealed that all 41 isolates were able to colonize cucumber roots without any significant difference. Twenty-one of the Paenibacillus isolates were shown to contain the nifH gene, which is an indicator of $N_{2}$ fixation. However, the other 20 isolates, including the reference strain E681, did not incorporate the nifH gene. To investigate the diversity of the isolates, a BOX-PCR was performed, and the resulting electrophoresis patterns allowed the 41 Paenibacillus isolates to be divided into three groups (Groups A, B, and C). One group included Paenibacillus strains isolated mainly from barley or wheat, whereas the other two groups contained strains isolated from diverse plant samples. Accordingly, the present results showed that the Paenibacillus isolates collected from the rhizosphere of winter crops were diverse in their biological and genetic characteristics, and they are good candidates for further application studies.

• Journal of Microbiology and Biotechnology
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• 제30권7호
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• pp.1027-1036
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• 2020

Stipa purpurea is a unique and dominant herbaceous plant species in the alpine steppe and meadows on the Qinghai-Tibet Plateau (QTP). In this work, we analyzed the composition and diversity of the culturable endophytic fungi in S. purpurea according to morphological and molecular identification. Then, we investigated the bioactivities of these fungi against plant pathogenic fungi and 1-aminocyclopropane-1-carboxylate deaminase (ACCD) deaminase activities. A total of 323 fungal isolates were first isolated from S. purpurea, and 33 fungal taxa were identified by internal transcribed spacer primers and grouped into Ascomycota. The diversity of endophytic fungi in S. purpurea was significantly higher in roots as compared to leaves. In addition, more than 40% of the endophytic fungi carried the gene encoding for the ACCD gene. The antibiosis assay demonstrated that 29, 35, 28, 37 and 34 isolates (43.9, 53.1, 42.4, 56.1, and 51.5%) were antagonistic to five plant pathogenic fungi, respectively. Our study provided the first assessment of the diversity of culture-depending endophytic fungi of S. purpurea, demonstrated the potential application of ACCD activity and antifungal activities with potential benefits to the host plant, and contributed to high biomass production and adaptation of S. purpurea to an adverse environment.