• Title/Summary/Keyword: Rhizobacterial

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Induced of Systemic Resistance against Gray Leaf Spot in Pepper by Enterobacter Species Isolated from Family Gramineae Plants in Dok-do (독도의 벼과식물로부터 분리된 Enterobacter spp.에 의한 고추의 흰별무늬병에 대한 전신유도저항성)

  • Son, Jin-Soo;Sumayo, Marilyn;Kang, Hyun-Uk;Kim, Byung-Soo;Kwon, Duck-Kee;Ghim, Sa-Youl
    • Microbiology and Biotechnology Letters
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    • v.40 no.2
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    • pp.135-143
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    • 2012
  • This study's aim is to isolate and characterize plant growth promoting Enterobacter species for the biological control of gray leaf spot in pepper. Screening was carried out from the rhizosphere of Agropyron tsukushiensi var. transiens (Hack.) Ohwi in Dok-do. Rhizobacterial isolates were partially identified by 16S rDNA sequencing and Enterobacter species were tested for plant growth promoting capabilities and the induction of systemic resistance in pepper against gray leaf spot caused by Stemphylium solani. Isolates were tested for production of indole-acetic acid and siderophore, and for phosphate solubilization. The application of isolates was effective in controlling gray leaf spot in pepper with E. asburiae (KNUC5007) and E. cancerogenes (KNUC5008 and KNUC5010) having the highest efficacy in reducing gray leaf spot severity. This is the first report of the biological control of gray leaf spot in pepper using rhizobacteria and it is hoped that this study will increase the utilization of Enterobacter species as plant growth promoters and biocontrol agents.

Interactions between Biosynthetic Pathway and Productivity of IAA in Some Rhizobacteria (근권에서 분리한 세균의 IAA 생합성 경로와 IAA 생성능과의 관계)

  • Kim, Woon-Jin;Song, Hong-Gyu
    • Korean Journal of Microbiology
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    • v.48 no.1
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    • pp.1-7
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    • 2012
  • This study explores the interaction between the production of indole-3-acetic acid (IAA), a typical phytohormone auxin and the role of IAA biosynthetic pathways in each IAA producing rhizobacterial strain. The bacterial strains were isolated from rhizosphere of wild plants and identified as Acinetobacter guillouiae SW5, Bacillus thuringiensis SW17, Rhodococcus equi SW9, and Lysinibacillus fusiformis SW13. A. guillouiae SW5 exhibited the highest production of IAA using tryptophan-dependent pathways among the 4 strains. When indole-3-acetamide (IAM) was added, Rhodococcus equi SW9 showed the highest IAA production of $3824{\mu}g/mg$ protein using amidase activity. A. guillouiae SW5 also showed the highest production of IAA using two pathways with indole-3-acetonitrile (IAN), and its nitrile hydratase activity might be higher than nitrilase. B. thuringiensis SW17 showed the lowest IAA production, and most of IAA might be produced by the amidase activity, although the nitrilase activity was the highest among 4 strains. The roles of nitrile converting enzymes were relatively similar in IAA synthesis by Lysinibacillus fusiformis SW13. Tryptophan-independent pathway of IAA production was utilized by only A. guillouiae SW5.

Antibacterial Effect of Bacteria Isolated from the Plant Rhizosphere against Pathogenic Bacteria of Fish (식물근권에서 분리한 세균의 어류질병세균에 대한 항균활성 효과)

  • Jeong, Ji-Woon;Park, So-Hyun;Kim, Dong-Hwi;Jeun, Yong-Chull;Heo, Moon-Soo
    • Journal of Life Science
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    • v.24 no.7
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    • pp.757-761
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    • 2014
  • Olive flounder (Paralichthys olivaceus) is an important aquaculture fish species in Jeju Island, South Korea. Due to the intensification of flounder fish farming, huge amounts of chemical antibiotics are used against several fish diseases. This has many harmful side effects on fish, as well as human consumers. Hence, an alternative to chemical antibiotic agents is needed for disease control. In this study, three strains of rhizobacteria (BRH433-2, TRH415-2, and THJ609-3) were isolated from the rhizosphere of plants. Assays of their antibacterial activity against fish pathogens, such as S. iniae, S. parauberis, V. anguillarum, and E. tarda, were performed with untreated broth culture (without cell separation), supernatant, and precipitated pellets separated by centrifugation. Among these, the cell suspension prepared from the precipitated pellet showed significant antimicrobial activity when compared with that of the untreated broth culture and centrifugal supernatant. These results indicate that the three isolated rhizobacterial strains exhibit antibacterial activity. Analysis of the 16S rDNA sequences of the BRH-433-2, THJ609-3, and TRH415-2 strains showed the highest similarity to Burkholderia gladioli (99.5%), Pseudomonas baetica (97.7%), and P. koreensis and P. baetica (98.4%), respectively. We suggest that the strains hold promise in disease management of fish.

Interactions between Indole-3-acetic Acid Producing Acinetobacter sp. SW5 and Growth of Tomato Plant (Indole-3-acetic acid를 생성하는 Acinetobacter sp. SW5와 토마토 식물 간의 상호작용)

  • Kwon, Hyeok-Do;Song, Hong-Gyu
    • Korean Journal of Microbiology
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    • v.50 no.4
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    • pp.302-307
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    • 2014
  • Many rhizobacteria can promote plant growth through various direct or indirect mechanisms, and their production of phytohormones such as indole-3-acetic acid (IAA) may have pronounced effects on growth and development of plants. Rhizobacterial strain isolated from rhizosphere of foxtail (Setaria viridis), Acinetobacter sp. SW5 produced 118.1 mg/L of IAA and 4.5 mg/L of gibberellin ($GA_3$) in brain heart broth medium at 2 and 1 day of incubation, respectively. In a pot test the lengths of stem and root and fresh weight of the germinated tomato seedlings treated with Acinetobacter sp. SW5 significantly increased by 26.3, 33.3, and 105.3%, respectively compared to those of the uninoculated control in 12 weeks of cultivation. When the root exudate secreted from tomato seedlings was analyzed by HPLC, 3.75 ng mg tomato $root^{-1}$ of tryptophan which is an IAA precursor was detected. Acinetobacter sp. SW5 could produce $4.06{\mu}M$ of IAA from root exudate from 8 tomato seedlings. Together with the capability of growth of Acinetobacter sp. SW5 in the tomato root exudates, this IAA secreted by bacteria might contribute to enhance the growth of tomato plants.