• The Plant Pathology Journal
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• 제32권2호
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• pp.136-144
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• 2016

Pseudomonas fluorescens pc78 is an effective biocontrol agent for soil-borne fungal diseases. We previously constructed a P43-gfp tagged biocontrol bacteria P. fluorescens pc78-48 to investigate bacterial traits in natural ecosystem and the environmental risk of genetically modified biocontrol bacteria in tomato rhizosphere. Fluctuation of culturable bacteria profile, microbial community structure, and potential horizontal gene transfer was investigated over time after the bacteria treatment to the tomato rhizosphere. Tagged gene transfer to other organisms such as tomato plants and bacteria cultured on various media was examined by polymerase chain reaction, using gene specific primers. Transfer of chromosomally integrated P43-gfp from pc78 to other organisms was not apparent. Population and colony types of culturable bacteria were not significantly affected by the introduction of P. fluorescens pc78 or pc78-48 into tomato rhizosphere. Additionally, terminal restriction fragment length polymorphism profiles were investigated to estimate the influence on the microbial community structure in tomato rhizosphere between non-treated and pc78-48-treated samples. Interestingly, rhizosphere soil treated with strain pc78-48 exhibited a significantly different bacterial community structure compared to that of non-treated rhizosphere soil. Our results suggest that biocontrol bacteria treatment influences microbial community in tomato rhizosphere, while the chromosomally modified biocontrol bacteria may not pose any specific environmental risk in terms of gene transfer.

• The Plant Pathology Journal
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• 제37권6호
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• pp.662-672
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• 2021

Plant growth-promoting bacteria improve plant growth under abiotic stress conditions. However, their effects on microbial succession in the rhizosphere are poorly understood. In this study, the inoculants of Bacillus mesonae strain H20-5 were administered to tomato plants grown in soils with different salinity levels (EC of 2, 4, and 6 dS/m). The bacterial communities in the bulk and rhizosphere soils were examined 14 days after H20-5 treatment using Illumina MiSeq sequencing of the bacterial 16S rRNA gene. Although the abundance of H20-5 rapidly decreased in the bulk and rhizosphere soils, a shift in the bacterial community was observed following H20-5 treatment. The variation in bacterial communities due to H20-5 treatment was higher in the rhizosphere than in the bulk soils. Additionally, the bacterial species richness and diversity were greater in the H20-5 treated rhizosphere than in the control. The composition and structure of the bacterial communities varied with soil salinity levels, and those in the H20-5 treated rhizosphere soil were clustered. The members of Actinobacteria genera, including Kineosporia, Virgisporangium, Actinoplanes, Gaiella, Blastococcus, and Solirubrobacter, were enriched in the H20-5 treated rhizosphere soils. The microbial co-occurrence network of the bacterial community in the H20-5 treated rhizosphere soils had more modules and keystone taxa compared to the control. These findings revealed that the strain H20-5 induced systemic tolerance in tomato plants and influenced the diversity, composition, structure, and network of bacterial communities. The bacterial community in the H20-5 treated rhizosphere soils also appeared to be relatively stable to soil salinity changes.

• Journal of Microbiology and Biotechnology
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• 제26권10호
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• pp.1755-1764
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• 2016

The application of Bacillus sp. in the biological control of plant soilborne diseases has been shown to be an environmentally friendly alternative to the use of chemical fungicides. In this study, the effects of bioorganic fertilizer (BOF) fortified with Bacillus amyloliquefaciens SQY 162 on the suppression of tomato bacterial wilt were investigated in pot experiments. The disease incidence of tomato wilt after the application of BOF was 65.18% and 41.62% lower at 10 and 20 days after transplantation, respectively, than in the control condition. BOF also promoted the plant growth. The SQY 162 populations efficiently colonized the tomato rhizosphere, which directly suppressed the number of Ralstonia solanacearum in the tomato rhizosphere soil. In the presence of BOF, the activities of defense-related enzymes in tomato were lower than in the presence of the control treatment, but the expression levels of the defense-related genes of the plants in the salicylic acid and jasmonic acid pathways were enhanced. It was also found that strain SQY 162 could secrete antibiotic surfactin, but not volatile organic compounds, to suppress Ralstonia. The strain could also produce plant growth promotion compounds such as siderophores and indole-3-acetic acid. Thus, owing to its innate multiple-functional traits and its broad biocontrol activities, we found that this antagonistic strain isolated from the tobacco rhizosphere could establish itself successfully in the tomato rhizosphere to control soilborne diseases.

• Molecules and Cells
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• 제45권7호
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• pp.502-511
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• 2022

Bacterial volatile compounds (BVCs) exert beneficial effects on plant protection both directly and indirectly. Although BVCs have been detected in vitro, their detection in situ remains challenging. The purpose of this study was to investigate the possibility of BVCs detection under in situ condition and estimate the potentials of in situ BVC to plants at below detection limit. We developed a method for detecting BVCs released by the soil bacteria Bacillus velezensis strain GB03 and Streptomyces griseus strain S4-7 in situ using solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS). Additionally, we evaluated the BVC detection limit in the rhizosphere and induction of systemic immune response in tomato plants grown in the greenhouse. Two signature BVCs, 2-nonanone and caryolan-1-ol, of GB03 and S4-7 respectively were successfully detected using the soil-vial system. However, these BVCs could not be detected in the rhizosphere pretreated with strains GB03 and S4-7. The detection limit of 2-nonanone in the tomato rhizosphere was 1 µM. Unexpectedly, drench application of 2-nonanone at 10 nM concentration, which is below its detection limit, protected tomato seedlings against Pseudomonas syringae pv. tomato. Our finding highlights that BVCs, including 2-nonanone, released by a soil bacterium are functional even when present at a concentration below the detection limit of SPME-GC-MS.

• The Plant Pathology Journal
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• 제35권4호
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• pp.362-371
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• 2019

Plant phenotype is affected by a community of associated microorganisms which requires dissection of the functional fraction. In this study, we aimed to culture the functionally active fraction of an upland soil microbiome, which can suppress tomato bacterial wilt. The microbiome fraction (MF) from the rhizosphere of Hawaii 7996 treated with an upland soil or forest soil MF was successively cultured in a designed modified M9 (MM9) medium partially mimicking the nutrient composition of tomato root exudates. Bacterial cells were harvested to amplify V3 and V4 regions of 16S rRNA gene for QIIME based sequence analysis and were also treated to Hawaii 7996 prior to Ralstonia solanacearum inoculation. The disease progress indicated that the upland MM9 $1^{st}$ transfer suppressed the bacterial wilt. Community analysis revealed that species richness was declined by successive cultivation of the MF. The upland MM9 $1^{st}$ transfer harbored population of phylum Proteobacteria (98.12%), Bacteriodetes (0.69%), Firmicutes (0.51%), Actinobacteria (0.08%), unidentified (0.54%), Cyanobacteria (0.01%), FBP (0.001%), OD1 (0.001%), Acidobacteria (0.005%). The family Enterobacteriaceae of Proteobacteria was the dominant member (86.76%) of the total population of which genus Enterobacter composed 86.76% making it a potential candidate to suppress bacterial wilt. The results suggest that this mixed culture approach is feasible to harvest microorganisms which may function as biocontrol agents.

• 미생물학회지
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• 제49권4호
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• pp.328-335
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• 2013

케라틴 단백질 분해 세균 Chryseobacterium sp. FBF-7(KACC 91463P)을 이용하여 대량생산한 닭우모 단백질 가수분해물(CPH)을 토마토에 처리한 결과, 토마토 줄기와 뿌리의 생장이 현저하게 증가되었다. 닭우모 가수분해물을 처리한 토마토 근권토양 내 세균군집 변동에 대한 계통학적 해석을 위하여 16S rRNA 유전자 서열을 기반으로 454 pyrosequencing을 수행하였다. 가수분해물을 처리하지 않은 토마토 근권토양(NCPH)의 16S rRNA 유전자 염기서열(3,281 reads)과 가수분해물을 처리한 토마토 근권토양(TCPH)의 16S rRNA 유전자 염기서열(2,167 reads)은 각각 6.33과 6.54의 다양성 지수를 나타내어 세균군집의 다양성에는 영향을 미치지 않는 것으로 확인되었다. 각 토마토 근권토양에는 총 19개의 문(phyla)의 세균이 존재하였고, 이중의 약 40%가 Proteobacteria이었다. Proteobacteria의 Bradyrhizobiaceae에 속하는 Bradyrhizobium, Agromonas, Nitrobacter 그리고 Afipia (BANA group)는 NCPH와 TCPH의 모든 근권토양에서 우점을 이루어 닭우모 가수분해믈 처리에 의해 토양 토착세균 군집에 영향을 미치지 않는 것으로 확인되었다.

• Mycobiology
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• 제46권2호
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• pp.147-153
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• 2018

Certain beneficial microorganisms isolated from rhizosphere soil promote plant growth and induce resistance to a wide variety of plant pathogens. We obtained 49 fungal isolates from the rhizosphere soil of paprika plants, and selected 18 of these isolates that did not inhibit tomato seed germination for further investigation. Based on a seed germination assay, we selected four isolates for further plant tests. Treatment of seeds with isolate JF27 promoted plant growth in pot tests, and suppressed bacterial speck disease caused by Pseudomonas syringae pathovar (pv.) tomato DC3000. Furthermore, expression of the pathogenesis-related 1 (PR1) gene was higher in the leaves of tomato plants grown from seeds treated with JF27; expression remained at a consistently higher level than in the control plants for 12 h after pathogen infection. The phylogenetic analysis of a partial internal transcribed spacer sequence and the b-tubulin gene identified isolate JF27 as Aspergillus terreus. Taken together, these results suggest that A. terreus JF27 has potential as a growth promoter and could be used to control bacterial speck disease by inducing resistance in tomato plants.

• 한국미생물·생명공학회지
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• 제22권6호
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• pp.679-684
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• 1994

For a biological control of root-knot nematode (Meloidogyne incognita) in tomato, efficiency of Bacillus thuringiensis subsp. indiana strain TH109 (BtTH109) on the nematode control was investigated. After the mixture of strain BtTH109 and wheat bran was treated into rhizosphere of the tomato plants with nematode eggs, the stem height and root growth of plants increased. And the juveniles and eggs of nematode are not found in both roots of tomatoes and pot soil after cultured broth of the strain BtTH109 treated 4 times at 3 day-interval into rhizosphere of the infected tomatoes.

• 미생물학회지
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• 제50권1호
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• pp.40-45
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• 2014

전 세계적으로 친환경 농업을 위해 식물생장촉진 근권세균을 이용한 미생물 비료에 대한 관심이 증가하고 있는데 투여하는 세균을 식물 근권에 보다 장기간 잔류시키기 위해 식물생장 촉진능이 있는 균주를 alginate bead에 고정화하여 식물생장을 조사하였다. 발아된 토마토 유묘에 Arthrobacter woluwensis ED를 $1{\times}10^6$ cells/g 로 처리하고 30일 재배 후 자라난 토마토의 shoot와 뿌리 길이 및 습윤과 건조중량을 측정한 결과 비접종 대조군과 비교하여 균주 현탁액 접종군은 각각 36.2, 59.0, 51.1과 37.5%씩 유의성 있게 증가하였으며 고정화 균주 접종군은 각각 42.0, 67.4, 62.5와 60.4%씩 유의성 있게 증가하였다. 고정화 균주 접종군은 균주 현탁액 접종군에 비하여 각각 6, 8, 11과 23% 증가하였다. 접종 균주가 식물 근권에서 유지되는 양상을 관찰하기 위해 denaturing gradient gel electrophoresis를 이용하여 토양세균 군집을 분석하였는데 균주 현탁액 접종군에서 ED 균주의 DNA band intensity는 접종일로부터 1주일까지 가장 높게 나타났으나 그 이후로 감소하여 접종 2주 후 비접종 대조군과 비슷한 band intensity를 나타내었다. 반면, 고정화 균주 접종군의 ED 균주 band intensity는 접종일로부터 초기에는 비접종 대조군과 비슷하였으나 이후 급격하게 증가하여 계속 높게 유지되어 3주까지 band intensity가 현탁액 접종군 보다 높았다. 따라서 alginate에 A. woluwensis ED를 고정하여 적용하는 방법이 현탁액 적용보다 식물 근권에 균주의 공급을 효과적으로 유지하면서 식물생장을 더욱 촉진하는 것으로 나타났다.

• 한국환경농학회지
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• 제40권1호
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• pp.49-59
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• 2021

BACKGROUND: Soil salinity causes reduction of crop productivity. Rhizosphere microbes have metabolic capabilities and ability to adaptation of plants to biotic and abiotic stresses. Plant growth-promoting bacteria (PGPB) could play a role as elicitors for inducing tolerance to stresses in plants by affecting resident microorganism in soil. This study was conducted to demonstrate the effect of selected strains on rhizosphere microbial community under salinity stress. METHODS AND RESULTS: The experiments were conducted in tomato plants in pots containing field soil. Bacterial suspension was inoculated into three-week-old tomato plants, one week after inoculation, and -1,000 kPa-balanced salinity stress was imposed. The physiological and biochemical attributes of plant under salt stress were monitored by evaluating pigment, malondialdehyde (MDA), proline, soil pH, electrical conductivity (EC) and ion concentrations. To demonstrate the effect of selected Bacillus strains on rhizosphere microbial community, soil microbial diversity and abundance were evaluated with Illumina MiSeq sequencing, and primer sets of 341F/805R and ITS3/ITS4 were used for bacterial and fungal communities, respectively. As a result, when the bacterial strains were inoculated and then salinity stress was imposed, the inoculation decreases the stress susceptibility including reduction in lipid peroxidation, enhanced pigmentation and proline accumulation which subsequently resulted in better plant growth. However, bacterial inoculations did not affect diversity (observed OTUs, ACE, Chao1 and Shannon) and structure (principle coordinate analysis) of microbial communities under salinity stress. Furthermore, relative abundance in microbial communities had no significant difference between bacterial treated- and untreated-soils under salinity stress. CONCLUSION: Inoculation of Bacillus strains could affect plant responses and soil pH of tomato plants under salinity stress, whereas microbial diversity and abundance had no significant difference by the bacterial treatments. These findings demonstrated that Bacillus strains could alleviate plant's salinity damages by regulating pigments, proline, and MDA contents without significant changes of microbial community in tomato plants, and can be used as effective biostimulators against salinity stress for sustainable agriculture.