• Korean Journal of Microbiology
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• v.44 no.2
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• pp.147-155
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• 2008

The diversity of sulfate reducing bacteria was investigated in different depths of sediments in Lake Sihwa, Korea and Lake Aha, China by PCR amplification, denaturing gradient gel electrophoresis (DGGE) and clone libraries targeting dissimilatory sulfite redectase (dsr) gene. In the analysis of DGGE band patterns, the community compositions of dsr gene in the sediments of both lakes were significantly different whereas bands in all depths of each environment revealed similar patterns. Bands from Lake Sihwa were produced much more than those from Lake Aha, demonstrating a higher diversity of dsr gene in Lake Sihwa. Total 68 clones containing dsr gene were obtained to analyze their sequences. Sequences from the sediment of Lake Sihwa were affiliated to Deltaproteobacteria, the Gram-positive thermophilic sulfate reducers belonging to the genus Desulforomaculum and archaeal thermophilic SRB belonging to the genus Archaeoglobus, whereas sequences from the sediments of Lake Aha were related to genus Desulfotomaculum. Clones retrieved from sediment of Lake Sihwa revealed a higher numbers than those of Lake Aha, demonstrating a higher diversity of dsr gene in Lake Sihwa. Most of clones (59%) were distantly related to the known cultivated SRB with $60\sim65%$ of similarity, which were clustered only the sequences from the environments showed less than 90% similarity. These habitat specific sequences suggested that the clustered dsr sequences represent species or groups of species that were indigenous to these environments. This study showed that these lakes have a specific bacterial communities having dsr gene distinct from those in other environments such as soil and marine ecosystems around the world.

• Korean Journal of Microbiology
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• v.46 no.3
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• pp.248-254
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• 2010

To define the optimum conditions for the mass production of four antifungal Pseudomonas spp. isolated from soil, we have investigated culture conditions and effects of various nutrient sources on the bacterial growth and evaluated antagonistic activity against Rhizoctonia solani and Sclerotinia homoeocarpa, plant pathogens. The optimum temperature and pH for the growth of these isolates were determined as pH 7.0 and $20^{\circ}$ or $25^{\circ}C$, respectively. Sucrose, tryptone, and $K_2HPO_4$ generally were more adequate for better growth as carbon, nitrogen and mineral source, respectively. The nutrient sources were also found to be very effective for high antifungal activities against R. solani and S. homoeocarpa. It was elucidated that YUD-F group (P. mandelii and P. fluorescens), which inhabit regions at relatively low temperature, had more broad spectrum and higher antifungal activity than YUD-O group (P. trivialis and P. jessenii) generally against R. solani and S. homoeocarpa. It is thought that the differences of the average temperature in the various habitats of Pseudomonas spp. influence the optimal growth temperature and antifungal activity. Especially, Pseudomonas spp. of YUD-O group showed the better antifungal activity against dollar spot caused by S. homoeocarpa, but showed relatively weaker antifungal activity against brown patch caused by R. solani.

• Korean Journal of Microbiology
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• v.46 no.2
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• pp.183-191
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• 2010

In this study, we isolated 179 bacterial strains using benzene, phenol, ethylbenzene, aniline, cumene, toluene as growth substrate from TCE contaminated soils and wastewaters. All the 179 strains were screened for TCE (30 mg/L) removal (growth substrate 0.2 g/L, $30^{\circ}C$, pH 7, cell biomass 1.0 g/L (w/v)) under aerobic condition for 21 days. EK2 strain using aniline showed the highest removal efficiency (74.4%) for TCE degradation. This strain was identified as Delftia acidovorans as the results of API kit, 16S rDNA sequence and fatty acid assay. In the batch culture, D. acidovorans EK2 showed the bio-degradation for TCE in the various TCE concentration (10 mg/L to 200 mg/L). However, D. acidovorans EK2 did not show the bio-degradation in the TCE 250 mg/L. D. acidovorans EK2 also show the removal efficiency (99.9%) for 12 days in the low concentration (1.0 mg/L). Optimal conditions to degrade TCE 200 mg/L were cell biomass 1.0 g/L (w/v), aniline 0.5 g/L, pH 7 and $30^{\circ}C$. Removal efficiency and removal rate by D. acidovorans EK2 strain was 71.0% and 94.7 nmol/h for 21 days under optimal conditions. Conclusion, we expect that D. acidovorans EK2 may contribute on the biological treatment in the contaminated soil or industrio us wastewater.

• Journal of Life Science
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• v.21 no.4
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• pp.589-595
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• 2011

This work focused on screening and characterizing antibiotic-producing actinomycetes to develop new antibiotics that can overcome the growing resistance of disease-causing microbes. One-hundred actinomycetes strains were isolated from soil samples from Chungcheongbuk-do, Korea using various kinds of actinomycetes isolation media, including a starch casein agar medium and potato dextrose agar (PDA). Among them, strain BCNU 1030 was determined to show strong antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA). Biochemical, physiological, and 16S rRNA sequence analyses indicated that strain BCNU 1030 belonged to the genus Streptomyces. Strain BCNU 1030 exhibited antibiotic activity against a wide range of bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentration (MIC) of BCNU 1030 dichloromethane extract was determined to be $0.78\;{\mu}g/ml$ for MRSA CCARM 3090. Therefore, Streptomyces sp. BCNU 1030 has potential for anti-MRSA drug development.

• Korean Journal of Microbiology
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• v.46 no.2
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• pp.157-161
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• 2010

Photosynthetic purple nonsulfur bacterial strains were isolated from the sediments collected from rice paddy fields and sludges of wastewater treatment plant, and their plant growth promoting capabilities were examined. Most well known phytohormones, auxin such as indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) and 5'-aminolevulinic acid (ALA) were detected by HPLC in the culture broth of these isolates. Among the isolated bacteria, Rhodopseudomonas faecalis D15 showed the highest production rate of 769.8 ${\mu}g$/mg protein of IAA, 1323 ${\mu}g$/mg protein of IBA and 7.4 mM/mg protein of ALA in the modified Biebl and Pfennig's medium. R. faecalis C9 showed the highest production rate of 20.82 ${\mu}g$/mg protein of gibberellin. In consequence, the root length and dry weight of the germinated tomato seedling treated with R. faecalis isolates were longer and heavier than those of uninoculated control after 15 days of incubation in the soil. Especially, the dry weight of germinated tomato seedling increased by 119.4% in C9-treated samples after 15 days. These purple nonsulfur bacteria may be utilized as environment-friendly biofertilizer in the agriculture.

• Korean Journal of Microbiology
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• v.38 no.2
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• pp.67-73
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• 2002

The cellular responses of soil-borne bacterium, Pseudomonas sp. HK-6 to explosive 2,4,6-trinitrotoluene (TNT) were examined. Two stress shock proteins (SSPs), approximately 70-kDa DnaK and a 60-kDa GroEL were found in HK-6 cells in response to TNT. Analyses of SDS-PAGE and Western blot using anti-DnaK and GroEL revealed that SSPs were induced in HK-6 cells exposed to 0.5 M of TNT far 6-12 hrs. The maximum induction of proteins was achieved at 8-hr incubation point after HK-6 cells'exposure to TNT. Similar SSPs were found to be induced in HK-6 cells by heat shock (shift of temperature, from $30^{\circ}C$ to $42^{\circ}C$) or cold shock (shift of temperature,$30^{\circ}C$ to $4^{\circ}C$).2D-PAGE of soluble protein tractions from the culture of Pseudomonas sp. HX-6 exposed to TNT demonstrated that approximately 450 spots were observed on the silver stained gels ranging from pH 3 to pH 10. Among them, 12 spots significantly induced and expressed in response to TNT were selected and analyzed. Approximately 60-kDa protein, which was assumed highly expressed on the gel, was used for amino acid sequencing. N-terminal microsequencing with in-gel digestion showed that N-terminal sequence of the TNT-induced protein, <$^1XXAKDVKFGDSARKKML^17$, shared extensive similarity with $^1XXAKDVKFGDSARKKML^17$, N-terminal sequence of (P48216) GroEL of Pseudomonas putida.

• Korean Journal of Microbiology
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• v.42 no.3
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• pp.223-229
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• 2006

To develop multifunctional microbial inoculant, an insluble phosphate-solubilizing bacterium with antifungal activity was isolated from plant rhizospheric soil. On the basis of its morphological, cultural and physiological characteristics and Biolog analysis, this bacterium was identified as Pseudomonas fluorescens RAF15. P. fluorescens RAF15 showed antifungal activities against phytopathogenic fungi Botrytis cinerea and Rhizoctonia solani. The optimal medium composition and cultural conditions for the solubilization of insoluble phosphate by P. fluorescens RAF15 were 1.5% of glucose, 0.005% of urea, 0.3% $MgCl_2{\cdot}6H_2\;0.01%\;of\;MgSO_4{\cdot}7H_2O\;0.01%,\;of\;CaCl_2{\cdot}2H_2O$, and 0.05% of NaCl along with initial pH 7.0 at $30^{\circ}C$. The soluble phosphate production under optimum condition was 863 mg/L after 5 days of cultivation. The solubilization of insoluble phosphates was associated with a drop in the pH of the culture medium. P. fluorescens RAF15 showed resistance against different environmental stresses like $10-35^{\circ}C$ temperature, 1-4% salt concentration and pH 2-11 range. The strain produced soluble phosphate to the culture broth with the concentrations of 971-1121 mg/L against $CaHPO_4$, 791-908 mg/L against $Ca_3(PO_4){_2}$, and 844 mg/L against hydroxyapatite, respectively. However, the strain produced soluble phosphate to the culture broth with the concentrations of 15 mg/L against $FePO_4$, and 5 mg/L against $AlPO_4$, respectively.

• Korean Journal of Microbiology
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• v.52 no.2
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• pp.212-219
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• 2016

Forty-nine pigments were extracted from the collections of 106 pigment producing bacteria from the plant rhizosphere soil. Antibacterial activity test was performed in the subjects of the extracted pigments with plant pathogenic bacteria including Xanthomonas axonopodis and Xanthomonas campestris, and with plant pathogenic fungi including Botrytis cinerea, Colletotrichum acutatum, and Fusarium oxysporum. The yellow pigment by Chryseobacterium sp. RBR9 and the red pigment by of Methylobacterium sp. RI13 showed the antibacterial activities against Xanthomonas axonopodis and Xanthomonas campestris. The violet pigment by Collimonas sp. DEC-B5 showed the antibacterial activity as well as the antifungal activities against Botrytis cinerea and Fusarium oxysporum. Especially, the violet pigment inhibited the growth of Botrytis cinerea more than 65% at MIC $20{\mu}M$. Upon the HPLC analysis result for the isolation of pigment with antifungal activity, violacein (91.6%) and deoxyviolacein (8.4%) were isolated for the pigment by Collimonas sp. DEC-B5. The production amount of the pigment was increased more than 10 times higher when D-mannitol 1.5% and yeast extract 0.2% were added as the nitrogen source to SCB medium. This study suggests that produced violacein by Collimonas sp. DEC-B5 will be effective to control strawberry gray-mold rot fungi by its preventive activity.

• Korean Journal of Microbiology
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• v.52 no.2
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• pp.148-156
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• 2016

This study examined effects of Enterobacter ludwigii SJR3 showing a high 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, on growth of tomato plant and its expression of stress-related genes under drought and salt stress. SJR3 strain was inoculated at $10^6cell/g$ soil to 4-week grown tomato plants, and drought and salt stresses were treated. After additional incubation for 1 week, root length, stem length, fresh weight and dry weight of tomato plants treated with SJR3 increased by 37.8, 37.2, 96.8 and 146.6%, respectively compared to those of uninoculated plants in drought stress environment, and they increased by 19.2, 25.4, 19.5, and 105.8%, respectively in salt stress environment. Proline content in tomato leaves increased significantly under stress conditions as one of a protecting substance against stresses, but proline contents in tomato treated with SJR3 decreased by 62.1 and 54.1%, respectively. Relative expression of genes encoding ACC oxidase, ACO1 and ACO4, ethylene response factor genes ERF1 and ERF4, and some other stress-related genes were examined from tomato leaves. Compared to the non-stressed tomato, expressions of all stress-related genes increased significantly in the stressed tomato, but gene expressions in the inoculated tomato were similar to those of no-stressed control tomato. Therefore, E. ludwigii SJR3 may play an important role in mitigating drought and salt stress in plants, and can increase productivity of crops under various abiotic stresses.

• Korean Journal of Microbiology
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• v.44 no.4
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• pp.326-332
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• 2008

Various bacteria were isolated from Korean soil samples based on their capability inhibiting the growth of MRSA strains. Among them, strain YK5 with the highest activity was a Gram positive sporulative bacillus with motility. It did not produce indole and no acid was formed from mannitol by the bacterium. The 16S rRNA sequence of the strain showed $95{\sim}98%$ homology with those of Paenibacillus spp.. The bacterial isolate shared the highest homology with that of P. elgii (98%), but was named as Paenibacillus incheonensis YK5 due to differences in physiological properties. Butanol extract of the P. incheonensis YK5 culture grown in SST medium at $37^{\circ}C$ for 96 hr showed a broad antimicrobial activity against Gram-positive (MRSA and Streptococcus pneumoniae) and negative (Pseudomonas aeruginosa, Salmonella spp., Shigella spp., Escherichia coli, Klebsiella pneumoniae) pathogenic bacteria and fungi (Cryptococcus neoformans and Trichophyton). The antimicrobial activity in the crude extract was stable in a broad range of temperature and pH, $20{\sim}100^{\circ}C$ and $3.0{\sim}6.0$, respectively. Therefore, the antimicrobial activity of P. incheonesis YK5 had potential as a novel antibiotics for pathogens including MRSA.