• 식물병연구
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• 제18권3호
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• pp.201-209
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• 2012

지자체 농업기술센터와 농과원에서 수집한 18개의 Bacillus subtilis 균주들이 보유하고 있는 기능성을 구명하기 위하여 항균활성을 비롯한 사이데로포아 생산, 질소고정능력, 인산가용화 능력 및 오옥신 생성능력을 조사하였다. B. subtilis 균주들은 대부분 입고병균(R. solani), 고추 탄저병균(C. acutatum), 채소류 시들음병균(F. oxysporum), 벼도열병균(M. oryzae), 고추 역병균(P. capsici)에 대하여 항균활성을 보였다. 대부분의 균주가 Siderophore와 오옥신 생성능력을 보였으며 질소고정능력도 함께 보유하고 있는 것으로 나타났다. 인산가용화능은 조사한 Bacillus 속 균주 중 단 한 균주에서 활성을 보였다. 대부분의 B. subtilis 균주가 고추 흰가루병 억제효과를 보였으나, 균주 간에는 방제효과에 있어서 큰 차이를 보이지 않았다. B. subtilis R2-1균주의 농업현장에서의 활용 가능성을 구명하기 위하여 2009년도에 강원도 화천의 유기재배농가에서 오이 흰가루병 방제용 미생물 농약으로 등록되어 사용되고 있는 '큐펙트'와 '탑시드'를 대조로 하여 방제효과를 검정하였다. 2009년도에 B. subtilis R2-1 처리시 방제효과는 37.7%로 '탑시드'(47.6%)보다는 낮았으나, '큐펙트'(25.7%)에 비해서는 높았다. 2010년도에는 B. subtilis R2-1의 고추 흰가루병 방제효과가 83.3%로 미생물 농약인 탑시드 보다도 높게 나타났다. B. subtilis R2-1균주의 발병억제 기작을 구명하기 위하여 B. subtilis R2-1균주와 미생물 농약(탑시드, 큐펙트)을 경엽 처리한 후 포자발아율을 계수한 결과, 미생물 농약인 큐펙트는 97.9%, 탑시드는 94.7% 억제하는데 비해서 B. subtilis R2-1균주는 84.2% 억제하는 것으로 나타났다. 앞으로 B. subtilis R2-1을 고농도로 배양할 수 있는 대량배양기술을 개발하고 항균활성 기능이 잘 발현되도록 제형화한다면 생물농약으로의 개발이 가능할 것으로 사료된다.

• The Plant Pathology Journal
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• 제40권4호
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• pp.346-357
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• 2024

This study was carried out to screen the antifungal activity against Colletotrichum acutatum, Colletotrichum dematium, and Colletotrichum coccodes. Bacterial isolate GP-P8 from pepper soil was found to be effective against the tested pathogens with an average inhibition rate of 70.7% in in vitro dual culture assays. 16S rRNA gene sequencing analysis result showed that the effective bacterial isolate as Bacillus siamensis. Biochemical characterization of GP-P8 was also performed. According to the results, protease and cellulose, siderophore production, phosphate solubilization, starch hydrolysis, and indole-3-acetic acid production were shown by the GP-P8. Using specific primers, genes involved in the production of antibiotics, such as iturin, fengycin, difficidin, bacilysin, bacillibactin, surfactin, macrolactin, and bacillaene were also detected in B. siamensis GP-P8. Identification and analysis of volatile organic compounds through solid phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS) revealed that acetoin and 2,3-butanediol were produced by isolate GP-P8. In vivo tests showed that GP-P8 significantly reduced the anthracnose disease caused by C. acutatum, and enhanced the growth of pepper plant. Reverse transcription polymerase chain reaction analysis of pepper fruits revealed that GP-P8 treated pepper plants showed increased expression of immune genes such as CaPR1, CaPR4, CaNPR1, CaMAPK4, CaJA2, and CaERF53. These results strongly suggest that GP-P8 could be a promising biocontrol agent against pepper anthracnose disease and possibly a pepper plant growth-promoting agent.

• The Plant Pathology Journal
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• 제23권3호
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• pp.161-165
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• 2007

Cultivation of a biocontrol agent on a certain medium often results in reduced biocontrol efficacy and alters physiological state. In our previous study, Burkholderia gladioli strain B543 with long-term subculture on tryptic soy agar resulted in significantly reduced biocontrol ability against cucumber damping-off caused by P. ultimum. Therefore, we investigated the influence of laboratory culturing media on biocontrol activity and physiological state of Burkholderia gladioli strain B543 by using long-term repeated culture on a certain medium. When isolate B543 were successionally cultured on King's B agar (KBA), tryptic soy agar, nutrient agar (NA), or soil extract agar more than 20 times, the isolate cultured on KBA or NA showed a significantly enhanced biocontrol efficacy and higher population density in the rhizosphere of cucumber compared to that of the others. However, the isolates cultured on KBA more than 20 times showed the lowest production of protease, siderophore, or antifungal substance(s), measured by skim milk agar, Chrome-Azurol-S agar, and potato dextrose agar amended with 10% of the culture filtrate, respectively. Our results suggest that adaptation to proper culturing medium can alter biocontrol ability and physiological state, and we must consider laboratory media in optimizing the use of biocontrol agents.

• 한국토양비료학회지
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• 제49권3호
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• pp.251-258
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• 2016

A rhizobacterium LPN-2, which showed strong antifungal activity and auxin producing ability, was isolated from a farmland in North Gyeongsang Province, South Korea. Based on analysis of the 16S rDNA sequence, strain LPN-2 was identified as a novel strain of Burkholderia and was designated as Burkholderia sp. LPN-2. In vitro experiments showed that the isolated stain LPN-2 significantly produced auxin within 48 hr incubation. In order to check for PGPR function we performed in vivo growth promoting test in different crops, including mung bean, pea and cabbage. Application of Burkholderia sp. LPN-2 showed dramatic growth promoting effect on all the tested plants. We also confirmed siderophore and cellulase productions by Burkholderia sp. LPN-2 using CAS blue agar and CMC plate test. Further treatment with LPN-2 and the crude culture broth was effective in suppressing anthracnose in vitro test and also reduced incidence and severity of anthracnose in apple and pepper. Taken together, we conclude that Burkholderia sp. LPN-2 might be used as organic fertilizer for effective crop production in organic farming.

• Mycobiology
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• 제48권5호
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• pp.392-398
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• 2020

This study was conducted to understand the dynamics of microbial communities of soil microorganisms, and their distribution and abundance in the indigenous microorganisms (IMOs) manipulated from humus collected from the forest near the crop field. The soil microorganisms originated from humus and artificially cultured microbial-based soil amendments were characterized by molecular and biochemical analyses. The bacterial population (2 × 10⁶~13 × 10⁶ CFU/g sample) was approximately 100-fold abundant than the fungal population (2 × 10⁴~8 × 10⁴ CFU/g sample). The 16S rDNA and ITS sequence analyses showed that the bacterial and fungal communities in humus and IMOs were mainly composed of Bacillus and Pseudomonas, and Trichoderma and Aspergillus species, respectively. Some of the bacterial isolates from the humus and IMOs showed strong inhibitory activity against soil-borne pathogenic fungi Fusarium oxysporum and Sclerotinia sclerotiorum. These bacteria also showed the siderophore production activity as well as phosphate solubilizing activity, which are requisite traits for biological control of plant pathogenic fungi. These results suggest that humus and IMOs could be a useful resource for sustainable agriculture.

• The Plant Pathology Journal
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• 제38권5호
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• pp.490-502
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• 2022

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial leaf blight (BLB) disease in rice (Oryza sativa L.) and it is among the most destructive pathogen responsible for severe yield losses. Potential bacterial biocontrol agents (BCAs) with plant growth promotion (PGP) abilities can be applied to better manage the BLB disease and increase crop yield, compared to current conventional practices. Thus, this study aimed to isolate, screen, and identify potential BCAs with PGP abilities. Isolation of the BCAs was performed from internal plant tissues and rhizosphere soil of healthy and Xoo-infected rice. A total of 18 bacterial strains were successfully screened for in vitro antagonistic ability against Xoo, siderophore production and PGP potentials. Among the bacterial strains, 3 endophytes, Bacillus sp. strain USML8, Bacillus sp. strain USML9, and Bacillus sp. strain USMR1 which were isolated from diseased plants harbored the BCA traits and significantly reduced leaf blight severity of rice. Simultaneously, the endophytic BCAs also possessed plant growth promoting traits and were able to enhance rice growth. Application of the selected endophytes (BCAs-PGP) at the early growth stage of rice exhibited potential in suppressing BLB disease and promoting rice growth.

• Journal of Microbiology and Biotechnology
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• 제34권2호
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• pp.296-305
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• 2024

Peach tree gummosis is a botanical anomaly distinguished by the secretion of dark-brown gum from the shoots of peach trees, and Botryosphaeria dothidea has been identified as one of the fungal species responsible for its occurrence. In South Korea, approximately 80% of gummosis cases are linked to infections caused by B. dothidea. In this study, we isolated microbes from the soil surrounding peach trees exhibiting antifungal activity against B. dothidea. Subsequently, we identified several bacterial strains as potential candidates for a biocontrol agent. Among them, Bacillus velezensis KTA01 displayed the most robust antifungal activity and was therefore selected for further analysis. To investigate the antifungal mechanism of B. velezensis KTA01, we performed tests to assess cell wall degradation and siderophore production. Additionally, we conducted reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis based on whole-genome sequencing to confirm the presence of genes responsible for the biosynthesis of lipopeptide compounds, a well-known characteristic of Bacillus spp., and to compare gene expression levels. Moreover, we extracted lipopeptide compounds using methanol and subjected them to both antifungal activity testing and high-performance liquid chromatography (HPLC) analysis. The experimental findings presented in this study unequivocally demonstrate the promising potential of B. velezensis KTA01 as a biocontrol agent against B. dothidea KACC45481, the pathogen responsible for causing peach tree gummosis.

• 생명과학회지
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• 제27권1호
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• pp.72-77
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• 2017

S. Typhimurium SL1344는 성장을 위한 보조인자로 무기철이 요구된다. 철 킬레이트제인 ethylenediamine di-o-hydroxyphenylactic acid (EDDA)가 첨가 된 M9 최소배지에서 S. Typhimurium은 성장에 있어 철 이용이 완전하게 억제된다. 하지만, 세균이나 곰팡이와 같은 미생물들은 철이 부족한 환경에서 제한된 철을 이용하기 위해 사이드로포어를 생산한다. 사람에서 유래한 트랜스페린(hTf)-철 복합체를 M9 배지에 첨가한 조건에서 S. Typhimurium의 사이드로포어 생산은 완전하게 중단되었다. 반면, S. Typhimurium의 성장은 염화철($FeCl_3$)을 첨가한 조건과 동일한 수준으로 유지되었다. 이 결과는 사이드로포어의 생산 없이도 S. Typhimurium이 hTf에 부착된 철을 직접적으로 이용할 수 있다는 것을 알 수 있다. 돌연변이주의 구축과 이를 이용한 분석을 통하여 우리는 세균이 hTf-철 복합체를 직접적으로 이용할 수 있다는 것을 확인할 수 있었다.

• 한국균학회지
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• 제44권1호
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• pp.36-47
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• 2016

본 연구는 식물 근권에서 분리한 유용미생물 PA1, PA2, PA4, PA5, PA12 의 식물 생장 촉진능력과 식물 병원성 진균인 Colletotrichum acutatum, C. coccodes, C. gloeosporioides, C. dematium, Botrytis cinerea, Rhizoctonia solani, Sclerotinia minor 그리고 Fusarium sp.에 대한 생장억제능력을 평가하는데 그 목적이 있다. In vitro 실험에서 유용미생물의 식물 병원성 진균의 생장억제 능력을 확인하기 위해 세균배지인 TSA 배지와 곰팡이 배지인 PDA배지, 그리고 TSA와 PDA배지를 각각 50%씩 혼합한 배지(v/v, 1:1)에서 대치배양을 실시하였다. 그 결과 PDA배지에서는 PA2가 C. coccodes에 대해 65.5%로 가장 높은 억제능력을 보였으며, TSA배지에서는 PA2가 S. minor에 대해 96.5%로 가장 높은 억제력을 보였다. 또한 PDA와 TSA를 혼합한 배지에서는 PA2가 C. acutatum에 대해 58.5%로 가장 높은 억제능력을 보였다. 분리한 5균주 모두에서 식물병원성 진균에 대하여 생물적 방제 효과가 있음을 확인하였다. 또한 식물생장 촉진능력을 유발하는 원인물질을 탐색하기 위해 siderophore, protease, chitinase, hydrogen cyanide (HCN) 생성 유무를 확인하였고, phosphate solubilizing 실험을 실시하였다. 본 연구에서 사용된 유용미생물 5균주를 16s rDNA sequencing 결과 PA1, PA2는 Bacillus subtilis, PA4, PA5, PA12 각각 Bacillus altitudinis, Paenibacillus polymyxa, Bacillus amyloliquefaciens로 동정되었다.

• 식물병연구
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• 제26권1호
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• pp.8-18
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• 2020

고추는 한국의 주요 경제 작물 중 하나이지만 재배과정에서 Colletotrichum acutatum에 기인한 탄저병이 많이 발생한다. 이의 방제를 위해 길항균인 Bacillus subtilis YGB36을 선발하여 16S rRNA 염기서열 및 생리·생화학적 분석을 통해 Bacillus subtilis로 동정하고 이를 생물학적 방제제로 개발하고자 실험을 진행하였다. In vitro screening에서 YGB36은 Cylindrocarpon destructans에 강한 항균활성을 나타내었고, cellulase, protease, amylase, siderophore 생산 및 phosphate solubility를 보유하고 있었다. 이 균주의 배양액(10⁶ cfu/ml) 및 배양여액은 in vitro 실험에서 C. acutatum의 포자발아를 강하게 억제하였고, 고추 과실을 이용한 실내실험에서도 이 배양액이 탄저병 병반의 진전을 억제하였으며, 방제가는 65.7%로 나타났다. 아울러 YGB36배양액은 고추 종자의 발아 및 초기 뿌리 생장을 촉진하였고, 온실에서의 식물 생장을 촉진하였다. 기존 화학농약과의 혼용 가능성 조사 결과, YGB36은 실험에 사용한 모든 살충제에서 생존에 영향을 전혀 받지 않았으며, 살균제 21종 중 11종에서 잘 생존하였다. 따라서 YGB36균주는 고추 탄저병에 대한 생물농약으로서의 잠재적 가치가 상당한 것으로 판단된다.