• Journal of Applied Biological Chemistry
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• v.48 no.2
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• pp.79-83
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• 2005

While screening for nematicidal activity of bacterial origins, various pseudomonads strains were inhabited in tomato rhizosphere. One isolate designated as $PE_{10}$ was selected for studies on nematicidal properties and plant growth-promoting (PGP) activity and was identified as Pseudomonas aeruginosa based on morphological features, biochemical and physiological tests, and carbohydrate utilization. To investigate nematicidal activity, Meloidogyne incognita juvenile mortality was determined using $PE_{10}$ culture filtrate. Inhibition of strain $PE_{10}$ against Fusarium oxysporum was observed using dual culture technique. Strain $PE_{10}$ showed good siderophore activity, HCN and IAA production abilities, and growth and development enhancement of tomato.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.1
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• pp.58-66
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• 2011

Arsenic pollution is a serious global concern which affects all life forms. Being a toxic metalloid, the continued search for appropriate technologies for its remediation is needed. Phytoremediation, the use of green plants, is not only a low cost but also an environmentally friendly approach for metal uptake and stabilization. However, its application is limited by slow plant growth which is further aggravated by the phytotoxic effect of the pollutant. Attempts to address these constraints were done by exploiting plant-microbe interactions which offers more advantages for phytoremediation. Several bacterial mechanisms that can increase the efficiency of phytoremediation of As are nitrogen fixation, phosphate solubilization, siderophore production, ACC deaminase activity and growth regulator production. Many have been reported for other metals, but few for arsenic. This mini-review attempts to present what has been done so far in exploring plants and their rhizosphere microbiota and some genetic manipulations to increase the efficiency of arsenic soil phytoremediation.

• Journal of Microbiology
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• v.38 no.1
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• pp.1-7
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• 2000

Eight strains of Aeromonas hydrophila isolated from diseased trout in Korea were characterized and compared with an American type strain by various methods including biochemical and physiological tests, PCR, randomly amplified polymorphic DNA (RAPD), plasmid profiling, and gel electrophoresis of total, membrane, and extracellular proteins. Virulence factors such as surface array proteins, cytotoxin, hemolysin, haemagglutinin, and protease were also investigated. The Korean strains showed heterogeneity in Iysine decarboxylase production, utilization of various carbon sources, and production of acetoin. Five strains had the same profiles of total and membrane proteins. Six strains haemagglutinated with trout red blood cells (RBCs) which was inhibited by fucose, galactose, and mannose, except for No. 1 where haemagglutination was inhibited by only galactose and mannose, but not by fucose. Four isolates haemagglutinated with human RBCs which was inhibited by fucose and mannose yet not by galactose. The type strain haemagglutinated only with trout RBCs which was inhibited by fucose, galactose, and mannose. Every isolate secreted protease, hemolysin, cytotoxin, and siderophore, but no enterotoxin. Results showed that the Korean isolates, except for No.7, had very different biochemical and molecular characteristics from those of the American type strain.

• The Korean Journal of Pesticide Science
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• v.17 no.4
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• pp.379-387
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• 2013

In order to improve practical utility of agro-microorganisms (AMs) which had been cultured and disseminated to promote plant growth and to control crop diseases, 51 isolates of AMs were collected from 18 agricultural extension centers in local government and screened for multi-functions such as antifungal activity, activities of phosphorus solubilization, IAA and siderophore production, nitrogen fixation, and hydrolytic enzyme activity. Finally we selected one isolate showing good antifungal activity and multi-functions related to plant growth and disease control. The selected isolate, Paenibacillus polymyxa CW, showed good inhibitory effect against plant pathogens, Pyricularia gresea, Colletotrichum acutatum, Fusarium oxysporum, Phomopsis sp., Aspergillus niger, Rhizoctonia solani and Phytophthora capsici. Suppressive effect of P. polymyxa CW against the used plant pathogens except for R. solani was much higher than that of P. polymyxa AC-1 storing in National Academy of Agricultural Science. We found P. polymyxa CW isolate showed good activity in siderophore and IAA formation, and nitrogen fixation. With P. polymyxa CW isolate, siderophore formation activity was similar to that of P. polymyxa AC-1, but IAA formation and nitrogen fixation activity was much higher than that of P. polymyxa AC-1. However neither P. polymyxa CW nor P. polymyxa AC-1 showed hydrolytic enzyme (chitinase, pectinase and cellulase) activity. The treatment of P. polymyxa CW with culture suspension of different cell density ($10^8$, $10^7$. $10^6$ cfu/ml) showed that the highest density reduced incidence of red pepper powdery mildew by 68.3% after 10 days of application. As application density of P. polymyxa CW was decreased, its control efficacy was proportionally decreased. In addition, when P. polymyxa CW was treated to control tomato powdery mildew at the same concentrations and their control effects were investigated after 7 days of inoculation, disease incidence was 0.03, 19.5, 45.7%, respectively, compared to 56.3% that of untreated check. Like red pepper powdery mildew, increase of application density of P. polymyxa CW resulted in increase of its control efficacy proportionally. P. polymyxa CW showed a density-dependent control efficacy against red pepper and tomato powdery mildews. Therefore we think that mode of action of the antagonist for suppressing two powdery mildew diseases might be antibiosis and density of more than $10^8cfu/ml$ was needed to control effectively the two diseases. On this basis, we think that P. polymyxa CW can be a promising control agent for suppressing powdery mildews of red pepper and tomato.

• Journal of Environmental Science International
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• v.27 no.9
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• pp.771-780
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• 2018

To develope a microbial weed control agent, HCN-producing bacteria were isolated, and their characteristics were investigated. A selected strain of WA15 was identified as Pseudomonas koreensis by morphological, cultural, biochemical and 16S rRNA gene analyses. The conditions for HCN production was investigated by a One-Variable-at-a-Time (OVT) method. The optimal HCN production conditions were tryptone 1%, glycine 0.06%, NaCl 1%, and an initial pH and temperature of 5.0 and $30^{\circ}C$, respectively. The major component for HCN production was glycine. Under optimal conditions, HCN production was about 3 times higher than that of the basal medium. The WA15 strain had physiological activities, such as indoleacetic acid that was associated with the elongation of plant roots and siderophore and ammonification inhibiting fungal growth, and produced hydrolytic enzymes, such as cellulase, pectinase and lipase. The strain was able to inhibit the growth of phytopathogenic fungi, such as Rhizoctonia solani, Botrytis cinerea and Fusarium oxysporum, by the synergistic action of volatile HCN and diffusible antimicrobial compounds. A microscopic observation of R. solani that was teated with the WA15 strain showed morphological abnormalities of fungal mycelia, which could explain the role of the antimicrobial metabolites that were produced by the WA15 strain. The volatile HCN produced by the WA15 strain was also found to have insecticidal activity against termites. Our results indicate that Pseudomonas koreensis WA15 can be applied as a microbial agent for weed control and also as a termite repellent. Furthermore, it could be applied as a microbial termiticidal agent to replace synthetic insecticides.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.596-602
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• 2019

In September 2017, the rhizospheric soil of Tetragonia tetragonoides (Pall.) Kuntze was further sampled. One hundred and thirty eight species of microorganisms were isolated from the soil. Indole-3-acetic acid (IAA) production, siderophore production, and phosphate degradation were examined in order to confirm bacterial growth from isolated microorganisms. As a result, most strains were able to produce auxins or siderophores and to solubilize phosphate. In addition, 138 isolated strains were treated with tobacco extract and conferred pathogen resistance to host plants upon treatment. As a result, 35 strains that were able to reduce pathophysiology by more the 60% were selected. Among them, 6 strains with high induced systemic resistance (ISR) activity were found. All of these strains belong to the genus Bacillus according to the 16S rDNA sequence analysis. Bacillus aryabhattai KUDC6619 showed outstanding effects with reduced infection in tobacco and pepper plants. Probably, these Bacillus species play a beneficial role by association with T. tetragonoides for its survival in the harsh conditions found on the island of Dokdo.

• Korean Journal of Microbiology
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• v.52 no.3
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• pp.254-259
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• 2016

Acinetobacter sp. B-W producing siderophore, 2, 3-dihydroxybenzoic acid (DHB) was analyzed for plasmid content. Strain B-W harbored plasmid of 20 kb in size. Growth at $43^{\circ}C$ was effective in producing mutant cured of plasmid of strain B-W. This mutant lost the ability to produce 2, 3-DHB. Formation of siderophore halos on the chrome azurol S (CAS) agar medium was not detected by cured strain B-W. pHs of supernatants of wild type strain B-W and cured mutant grown in glucose and $MnSO_4$ containing medium at $28^{\circ}C$ for 3 days were 4.5 and 8.5, respectively. Antibiotic resistance against ampicillin, actinomycin D, bacitracin, lincomycin, and vancomycin was lost in cured mutant. Plasmid curing of strain B-W resulted in drastic reduction of minimal inhibitory concentration (MIC) of several antibiotics. E. coli $DH5{\alpha}$ was transformed with plasmid isolated from strain B-W. The transformant E. coli $DH5{\alpha}$ harbored a plasmid of the same molecular size as that of the donor plasmid. Transformant E. coli $DH5{\alpha}$ produced 2, 3-DHB and contained antibiotic resistant ability. Thus a single plasmid of 20 kb seemed to be involved in 2, 3-DHB production. Genes encoding resistance to antibiotics were also supposed to be located on this plasmid.

• The Korean Journal of Mycology
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• v.47 no.3
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• pp.259-269
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• 2019

Brown spot and sheath rot of rice are caused by fungal pathogens such as Curvularia lunata, Cochliobolus miyabeanus, and Sarocladium oryzae, and cause losses such as reduced rice yield and quality, which is an enormous problem with serious long-term effects. To search biological control agents of phytopathogenic fungi, five kinds of useful Bacillus-like isolates which are excellent in extracellular enzyme activity and produce siderophore were selected from paddy soil of Sunchang in Korea. The selected isolates were tested for excellent antifungal activity against three of the phytopathogenic fungi that frequently occur in rice, and JSRB 177 strain had the most excellent antifungal activity. Based on the experimental results, JSRB 177 is finally selected as a candidate for biological control and identified to Bacillus subtilis through 16S rRNA sequence analysis. In addition, physiological characteristics of JSRB 177 confirmed by analysis of carbohydrate fermentation patterns and enzyme production ability. Based on the above results, JSRB 177 is expected to be used as a biological control agent for the rice pathogenic fungi. In the future, further studies related to industrialization such as port test and establishment of mass production process are needed.

• Microbiology and Biotechnology Letters
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• v.49 no.4
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• pp.576-586
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• 2021

The purpose of this study was to evaluate the antifungal activity, plant-growth-promoting activity, and mineral solubilization ability of 10 species of phytopathogenic fungi to select a Bacillus sp. from rhizosphere soils and roots that can be used as a microbial agent. The antifungal activity for phytopathogenic fungi varied based on the Bacillus sp. Among the selected strains, DDP4, DDP16, DDP148, SN56, and SN95 exhibited antifungal activity for nine or more species of phytopathogenic fungi. Regarding nitrogen-fixation ability, all Bacillus sp. showed similar levels of activity, and siderophore production ability was relatively high in ANG42 and DDP427. The indole-3-acetic acid production abilities were in the range of 1.83-67.91 ㎍/ml, with variations in activity based on the Bacillus sp. One strain with a high activity was selected from each species, and their mineral solubilization abilities were examined. Most Bacillus sp. could solubilize phosphoric acid and calcium carbonate, and DDP148 and SN56 could solubilize silicon and zinc, respectively. These results suggested that Bacillus sp. can be considered potential multi-purpose microbial agents for plant growth promotion and disease prevention.

• Journal of Environmental Science International
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• v.22 no.11
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• pp.1457-1464
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• 2013

We investigated the optimal conditions for keratinase production by feather-degrading Pseudomonas geniculata H10 using one variable at a time (OVT) method. The optimal medium composition and cultural condition for keratinase production were determined to be glucose 0.15% (w/v), beef extract 0.08% (w/v), $KH_2PO_4$ 0.12% (w/v), $K_2HPO_4$ 0.02% (w/v), NaCl 0.07% (w/v), $MgSO_4{\cdot}7H_2O$ 0.03%, $MgCl_2{\cdot}6H_2O$ 0.04% along with initial pH 10 at 200 rpm and $25^{\circ}C$, respectively. The production yield of keratinase was 31.6 U/ml in an optimal condition, showing 4.6-fold higher than that in basal medium. The strain H10 also showed plant growth promoting activities. This strain had ammonification activity and produced indoleacetic acid (IAA), siderophore and a variety of hydrolytic enzymes such as protease, lipase and chitinase. Therefore, this study showed that P. geniculata H10 could be not only used to upgrade the nutritional value of feather wastes but also useful in situ biodegradation of feather wastes. Moreover, it is also a potential candidate for the development of biofertilizing agent applicable to crop plant soil.