• Korean Journal of Microbiology
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• v.44 no.2
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• pp.156-163
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• 2008

In this study, we isolated 32 strains of kerosene degrading bacteria from oil contaminated soil by enrichment culture. Isolates were screened for kerosene degradation efficiencies and K14 were selected which had the highest removal efficiency for 1,000 mg/L of kerosene. K14 were identified as Pseudomonas aeruginosa by morphological, biochemical test and 16S rDNA analysis. The optimal culture condition were determined as initial inoculated cell concentration, 1.0 g/L; substrate concentration, 1,000 mg/L; temperature $30^{\circ}C$; pH 7. When we enforced batch test in this condition, K14 degraded 72% of kerosene with 1,000 mg/L during 72 hr. And, at low concentration (200 mg/L), K14 degraded 95.8% of kerosene during 48 hr. As a result, kerosene biodegradation by Pseudomonas aeruginosa K14 could be useful for clean up of groundwater and soil contaminated with crude oil.

• Research in Plant Disease
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• v.14 no.1
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• pp.32-36
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• 2008

Bacterial wilt caused by Ralstonia solanacearum has become a severe problem on tomato in Korea and no effective control measures are available yet. Pseudomonas species play key roles for the biocontrol of many plant diseases especially in soil. A rhizobacterial population of 150 Pseudomonas strains, isolated from the rhizosphere soil of various plants grown at different sites, was screened for 2,4-diacetylphloroglucinol producing gene (PhlD) by PCR. Two strains (P83 and P84) among them were found to be phlD positive. When the isolates were analysed by 16S rDNA (Sensu Stricto), all isolates yielded amplified products of 1,018bp. Of the 150 isolates of Pseudomonas spp., a bacterial strain P. putida P84 isolated from tomato rhizosphere showed to suppress a wide range of phytopathogenic bacteria in vitro. The best source of carbon for P84 strain were glucose, arabinose, inositol and melibiose. In greenhouse experiments, P84 strain suppressed the development of bacterial wilt in tomato with a control value of 60%.

• The Plant Pathology Journal
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• v.36 no.3
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• pp.244-254
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• 2020

Gom-chwi (Ligularia fischeri) is severely infected with Phytophthora drechsleri, the causal organism of Phytophthora root rot, an economically important crop disease that needs management throughout the cultivation period. In the present study, Phytophthora root rot was controlled by using bacterial isolates from rhizosphere soils collected from various plants and screened for antagonistic activity against P. drechsleri. A total of 172 bacterial strains were isolated, of which, 49 strains showed antagonistic activities by dual culture assay. In the seedling assay, six out of the 49 strains showed a predominant effect on suppressing P. drechsleri. Among the six strains, the ObRS-5 strain showed remarkable against P. drechsleri when treated with seed dipping or soil drenching. The ObRS-5 strain was identified as Enterobacter asburiae based on 16S ribosomal RNA gene sequences analysis. The bacterial cells of E. asburiae ObRS-5 significantly suppressed sporangium formation and zoospore germination in P. drechsleri by 87.4% and 66.7%, respectively. In addition, culture filtrate of E. asburiae ObRS-5 also significantly inhibited sporangium formation and zoospore germination by 97.0% and 67.6%, respectively. Soil drenched bacterial cells, filtrate, and culture solution of E. asburiae ObRS-5 effectively suppressed Phytophthora root rot by 63.2%, 57.9%, and 81.1%, respectively. Thus, E. asburiae ObRS-5 could be used as a potential agent for the biological control of Phytophthora root rot infecting gom-chwi.

• Korean Journal of Food Science and Technology
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• v.32 no.2
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• pp.439-443
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• 2000

In order to evaluate the safety of greenhouse horticulture products in Korea, we carried out this work by screening of Fusarium species, which produce deoxynivalenol (DON) from greenhouse horticulture in Western Gyeongnam and Northern Gyeongbuk, Korea. For this study, high sensitive enzyme-linked immunosorbent assay, ALP/NADP method, was applied to detection of DON by enzyme amplification system. From 192 samples of greenhouse horticulture soil and its products, 103 isolates of Fusarium species were obtained. The isolates were cultured at 28C for 15 days and the cultured mediums were extracted by ethyl acetate. The production of DON was verified by thin layer chromatography (TLC). As the results of TLC, 8 strains were identified as DON producing strain. We screened potential producers of DON by ALP/NADP. The levels of DON production were shown from 0.007 to 1.21 g/ml of YES medium. The maximum DON producing strain No. 32-D-3 was isolated from soil in Namhae, Korea. In conclusion, the above results indicate that DON producing fungi contaminated greenhouse horticulture products in Korea. Therefore, further studies are required to accumulate more detailed data about the contamination of DON in various cereals.

• Journal of Soil and Groundwater Environment
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• v.17 no.4
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• pp.51-62
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• 2012

Effects of climate change on groundwater system requires understanding the groundwater system in temporal and spatial scales through the long-term monitoring. In this study, the spatio-temporal variations of groundwater were analyzed through the continuous observation of water level, electrical conductivity (EC) and water temperature with automatic data-loggers and sampling in a Gwangneung catchment, Korea, for the four years from 2008 to 2011. Groundwater monitoring were performed at the nest-type wells, MW1 and MW2, located in upsteam and downstream of the catchment, respectively. During the survey period, both the total amount of annual precipitation and the frequency of concentrated rainfall have increased resulting in the elevation of runoff. Water level of MW1 showed no significant fluctuations even during the rainy season, indicating the confined groundwater system. In contrast, that of MW2 showed clear seasonal changes, indicating the unconfined system. The lag-time of temperature at both wells ranged from one to three months depending on the screened depths. Results of chemical analyses indicated that major water compositions were maintained constantly, except for the EC decreases due to the dilution effect. Values of the stable-isotope ratios for oxygen and deuterium were higher at MW2 than MW1, implying the confined system at the upstream area could be locally developed.

• Microbiology and Biotechnology Letters
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• v.50 no.2
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• pp.245-254
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• 2022

Cellulases are a group of biocatalyst enzymes that are capable of degrading cellulosic biomass present in the natural environment and produced by a large number of microorganisms, including bacteria and fungi, etc. In the current study, we isolated, screened and characterized cellulase-producing bacteria from soil. Three cellulose-degrading species were isolated based on clear zone using Congo red stain on carboxymethyl cellulose (CMC) agar plates. These bacterial isolates, named as HB2, HS5 and HS9, were subsequently characterized by morphological and biochemical tests as well as 16S rRNA gene sequencing. Based on 16S rRNA analysis, the bacterial isolates were identified as Bacillus cerus, Bacillus subtilis and Bacillus stratosphericus. Moreover, for maximum cellulase production, different growth parameters were optimized. Maximum optical density for growth was also noted at pH 7.0 for 48 h for all three isolates. Optical density was high for all three isolates using meat extract as a nitrogen source for 48 h. The pH profile of all three strains was quite similar but the maximum enzyme activity was observed at pH 7.0. Maximum cellulase production by all three bacterial isolates was noted when using lactose as a carbon rather than nitrogen and peptone. Further studies are needed for identification of new isolates in this region having maximum cellulolytic activity. Our findings indicate that this enzyme has various potential industrial applications.

• Microbiology and Biotechnology Letters
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• v.51 no.4
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• pp.474-483
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• 2023

Members of the genus Streptomyces produce more than 70% of antibiotics. The rise in antibiotic resistance globally enhanced the search for novel species with the ability to produce new bioactive compounds. This study was initiated to investigate different regions in Jordan for previously uncultured and rare Streptomyces species capable of producing novel antimicrobial compounds especially active against bacteria resistant to antibiotics. A total of 191 Streptomyces strains were isolated from 26 soil samples collected from different geographic regions in Jordan. Isolates were characterized based on colony and cellular morphology as well as using 16S rRNA gene sequencing. These isolates were screened for their ability to produce antibiotics by the perpendicular-cross streak method, and then tested by well diffusion method against tested pathogens. Fifty-four isolates showed potential to produce antimicrobial products especially active against resistant bacteria, 20.1% of the isolates showed inhibitory effect against Staphylococcus aureus, 16.9% against clinical MSSA strains, and 18.0% against MRSA: whereas only 4.2% against Esherichia coli, 3.2% against Klebsiella pneumonia, 2.7% against Pseudomonas aeruginosa, and 10.0% against clinical Candida albicans. Three isolates were selected for further identification due to their antibacterial activity against S. aureus, MRSA, and MSSA. These isolates were identified as follows; Streptomyces aburaviensis DSa3, Streptomyces alboniger SAb7 and Streptomyces misionensis ZAb2, based on cultural, biochemical characteristics and molecular analysis of the 16S rRNA.

• Applied Biological Chemistry
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• v.48 no.4
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• pp.345-351
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• 2005

To access the natural products of uncultured microorganisms, we constructed and screened the metagenomic DNA libraries by using a cosmid vector and DNA inserts isolated directly from soil. Initial screening of the libraries in Escherichia coli resulted in the isolation of several clones that produce a dark brown color when grown in LB medium. One of the positive clones, designed pYS85C, was transposon mutagenized and the DNA surrounding the transposon insertions in cosmids that no longer conferred the production of brown pigment to E. coli was sequenced. Annotation of the pYS85C sequence obtained from the transposon mutagenesis experiment indicated a single 393 amino acid open reading frame (ORF) with a molecular mass of about 44.5 kDa, predicted to be a 4-hydroxyphenylpyruvate dioxygenases (HPPDs), was responsible for the observed brown pigment. In a BLAST search against deposited sequence, the translated protein from this ORF showed moderate-level identity (>60%) to the other known HPPDs and was most conserved in the C-terminal region of the protein. These results show that genes involved in natural product synthesis can be cloned directly from soil DNA and expressed in a heterologous host, supporting the idea that this technology has the potential to provide novel natural products from the wealth of environmental microbial diversity and is a potentially important new tool for drug discovery.

• The Korean Journal of Pesticide Science
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• v.4 no.4
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• pp.12-18
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• 2000

In order to artificially reduce the quinclorac residue in aqueous solution and soil, six potential photosensitizers were screened for their effectiveness in enhancing the photodegradation. The degraded amount of quinclorac in distilled water by sunlight was minor compared to that in the dark, indicating that there was little direct photolysis. The photodegradation ratio of quinclorac in methanol was 40.3%. Whereas, the ratios in the presence of photosensitizers PS-1 (aromatic ketone), PS-3 (polycyclic quinone), and PS-6 (inorganic semiconductor) were 96.6, 72.7, and 95.7%, respectively, showing the most photosensitizing effects. In sand, PS-3 was more effective than any other photosensitizer PS-1 (19.6%), PS-3 (64.1%) and PS-6 ($17.9{\sim}19.4%$). five photoproducts of quinclorac in methanol were identified by GC-MS and quinclorac added with the photosensitizer PS-1 gave three photoproducts. Photoproducts with an aldehyde group formed in methanol were confirmed by the reduction of sodium 3,5-dinitrosalicylate in the Lindsay's method. E. crus-galli war. oryzicola was not controlled by the quinclorac residues photodegraded at tile concentrations higher than 30 ppm of the photosensitizer PS-3 in a flooded rice paddy soil. These results indicate that the quinclorac residues in aqueous solution and soil can be degraded efficiently by tile photosensitizers PS-1, PS-3, and PS-6.

• Journal of Ginseng Research
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• v.22 no.4
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• pp.223-228
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• 1998

As part of a study on the ability of fungicides to control disappearing root rot of ginseng (Panax quinquvdius) caused by Cylindruarpn destmtans, 15 fungicides were screened for toxicity to the fungus in vitro. Highly toxic fungicides were Benlate (benomyl), Thiram (thiram), and Orbit (propiconazole). EC5O values (mg a.i./L) were less than 1 and EC95 values were less than 10. Crown (carbathiin and thiabendazole), ASC-66835 (fluazinam), and UBI-2584 (tebuconazole) were moderately toxic, with EC5O values in the range 1-10 and EC95 values in the range 32-45. Weakly toxic fungicides (EC5O in the range 20-80, EC95 in the range 35-140) included UBI-2643 (thiabendazole), UBI-2565 (cyproconazole), and Vitaflo-280 (carbathiin and thiram). Anvil (hexaconazole), Vitaflo-250 (carbathiin), UBI-2383 (triadimenol), Daconil (chlorothalonil), CGA-173506 (fludioxonil), and CGA-169374 (difeno- conazole) were considered nontoxic to C. destmtan (EC5O 1.29->600, EC95>500). Relations between proportional inhibition of growth and concentration of fungicide were linear on arithmetic plots (Benlate, UBI-2643, UBI-2565, Vitaflo-280) or logarithmic plots (all other fungicides). Based on toxicity in vitro and formulation, it is recommended that Benlate, Orbit, and ASC-66835 be tested as soil drenches, and Benlate, Thiram, UBI-2584, and Crown be tested as seed treatments for controlling disappearing root rot.