• Korean Journal of Soil Science and Fertilizer
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• v.41 no.5
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• pp.348-353
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• 2008

With the aim to explore the possible role of phosphate-solubilizing bacteria in soil, we conducted a survey of phosphate-solubilizing microorganisms colonizing in upland and plastic film house soils. Soil EC, pH, organic matter, available phosphate, exchangeable cation such as potassium, calcium and magnesium, and total P of plastic film house soils were higher than those of upland soils. Phosphate-solubilizing bacteria population was higher in plastic film house soils than upland soils, but species of phosphate-solubilizing bacteria was more diverse in the upland soils than the plastic film house soils. There was significant positive correlation between phosphate solubilization and phosphate-solubilizing bacteria in soils. Bacillus, Cedecea, Brevibacillus, Paenibacillus, Pseudomonas, Serratia spp. were isolated from upland soils and Bacillus and Cellulomonas spp. were from plastic film house soils.

• KSBB Journal
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• v.13 no.5
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• pp.497-501
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• 1998

A fungus with high phosphate solubilizing activites was isolated from soil using potato dextrose agar-calcium phosphate medium and identified to Penicillium sp. PS-113, based on the morphological characteristics of conidiophore and conidia; flask shape of phialide, simple branching type of conidiophore, and columnar shape of conidial head, in malt extract agar and potato dextrose agar media. The optimum temperature ad initial pH to solubilize rock phosphate in potato dextrose broth-rock phosphate medium were 30$^{\circ}C$ and pH 8.0, respectively. In these conditions phosphate solubilizing activities of Penicillium sp. PS-113 against four types of insoluble phosphate like tricalcium-phosphate, aluminium phosphate, hydroxyapatite and rock phosphate were quantitatively determined. As results, this fungus highly produced free phosphates to the culture broth with the concentrations of 1,283 ppm against tricalcium-phosphate, 585 ppm against rock phosphate, 528 ppm against aluminium phosphate, and 242 ppm against hydroxyapatite, respectively.

• Korean Journal of Environmental Agriculture
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• v.26 no.1
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• pp.36-41
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• 2007

Phosphate-solubilizing microorganisms were isolated from soil around Kyungnam and Kyungbook regions using potato dextrose agar-calcium phosphate medium. A fungus with the greatest phosphate-solubilizing activity was selected and identified to Aspergillus sp. PS-104, based on the morphological characteristics of conidiophore and conidia; unbranching type of conidiophore, terminally swelling of conidiophore and septate of mycelium, in malt extract agar and potato dextrose agar media. The optimum temperature and initial pH to solubilize rock phosphate in potato dextrose broth-rock phosphate medium were $30^{\circ}C$ and pH 7.0, respectively. In these optimum conditions, phosphate-solubilizing activities of Aspergillus sp. PS-104 against four twos of insoluble phosphate, tricalcium phosphate, aluminium phosphate, hydroxyapatite and rock phosphate, were quantitatively determined. As result, the maximum phosphate-solubilizing activity was obtained with tricalcium-phosphate (1,900 ppm) while minimum activity was obtained with hydroxyapatite (320 ppm). Futhermore, phosphate-solubilizing activity of Aspergillus sp. PS-104 was found higher when treated with nitrates as compared to the ammonium salts as a nitrogen sources.

• Journal of Life Science
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• v.23 no.2
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• pp.242-248
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• 2013

The objective of this study was to develop a mineral phosphate-solubilizing bacterium as a biofertilizer. A mineral phosphate-solubilizing bacterium HR-1019 was isolated from cultivated soils. It was identified as Bacillus subtilis by 16S rDNA analysis. The phosphate-solubilizing activities of the HR-1019 strain against three types of insoluble phosphate, hydroxyapatite, tri-calcium phosphate, and aluminum phosphate were quantitatively determined. When 5% of glucose concentration was used as a carbon source, the strain showed marked mineral phosphate-solubilizing activity. Mineral phosphate solubilization was directly related to pH drop in the culture solution of the strain. The pathogenic activity and antifungal effects of the HR-1019 strain were measured inclear zones formed in PDA media.

• Microbiology and Biotechnology Letters
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• v.27 no.1
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• pp.1-7
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• 1999

A fungus, Penicillium sp. PS-113, isolated from soil showed the high phosphate-solubilizing activity in patato dextrose broth-rock phosphate to produce free phosphates to the culture broth with the concentrations of 585 ppm against rock phosphate. In this medium, the optimum temperature and initial pH to solubilize rock phosphate were 30$^{\circ}C$ and pH 7.5, respectively. In order to make the mass production of the conidia from this fungus, we cultured in on various solid-based media like barley, corn, wheat, rice, rice bran, and compost. As a result, the fungus highly produced conidia ranging from 2.1 to $5.1{\times}10_9$ conidia/g${\cdot}$media on these solid media except compost-based medium, which was 0 times less than others. Effects of inoculation of the phosphate solubilizing fungus as a biofertilizer were studied in perlite-based pot cropped with Zea mays Suwon 19. Inoculation of Penicillium sp. PS-113 increased in plant height (1.4 times), plant weight (5.2~8.1 times) and root length (1.1~1.2 times) at 60-day cultivation, compared to Hogland solution either without $NH_4H_2PO_4$ or displace $NH_4H_2PO_4$ to powdered rock phosphate, a phosphorus source for plant growth.

• Journal of Life Science
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• v.10 no.1
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• pp.64-65
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• 2000

Insoluble phosphate-solubilizing bacteria are routinely screened by a plate assay method using Pikovskaya agar and a modified Pikovskaya medium. A modified Pikovskaya medium to improve the clarity of the yellow-colored halo has not necessarity improved the plate assay. Colonies of phosphate-solubilizing bacteria tested could be redily selected after 48 h of incubation by green-colored colony formation on plate in which bromcresol green(BCG) was included. Among them, two bacterial strains did not produce distinct yellow halos after 48 h of incubation. We suggest that the green colony formation on plate medium containing BCG is advantageous ofr rapid isolating phosphate-solubilizing bacteria directly from soil.

• Journal of Microbiology and Biotechnology
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• v.27 no.4
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• pp.844-855
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• 2017

Phosphate-solubilizing bacteria (PSB) have the ability to dissolve insoluble phosphate and enhance soil fertility. However, the growth and mineral phosphate solubilization of PSB could be affected by exogenous soluble phosphate and the mechanism has not been fully understood. In the present study, the growth and mineral phosphate-solubilizing characteristics of PSB strain Burkholderia multivorans WS-FJ9 were investigated at six levels of exogenous soluble phosphate (0, 0.5, 1, 5, 10, and 20 mM). The WS-FJ9 strain showed better growth at high levels of soluble phosphate. The phosphate-solubilizing activity of WS-FJ9 was reduced as the soluble phosphate concentration increased, as well as the production of pyruvic acid. Transcriptome profiling of WS-FJ9 at three levels of exogenous soluble phosphate (0, 5, and 20 mM) identified 446 differentially expressed genes, among which 44 genes were continuously up-regulated when soluble phosphate concentration was increased and 81 genes were continuously down-regulated. Some genes related to cell growth were continuously up-regulated, which would account for the better growth of WS-FJ9 at high levels of soluble phosphate. Genes involved in glucose metabolism, including glycerate kinase, 2-oxoglutarate dehydrogenase, and sugar ABC-type transporter, were continuously down-regulated, which indicates that metabolic channeling of glucose towards the phosphorylative pathway was negatively regulated by soluble phosphate. These findings represent an important first step in understanding the molecular mechanisms of soluble phosphate effects on the growth and mineral phosphate solubilization of PSB.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.94.2-95
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• 2003

E. intermedium 60-2G possessing a strong ability to solubilize insoluble phosphate, has plant growth-promoting activity, induced systemic resistance activity against scab pathogen in cucumber, and antifungal activity against various phytopathogenic fungi. The phosphate solubilizing activity of 60-2G may be mainly accomplished by production of gluconic acid through a direct extracellular oxidation of glucose by glucose dehydrogenase that required a PQQ cofactor for its activation. A pqq gene cluster conferred Phosphate-solubilizing activity in E. coli DH5${\alpha}$ was cloned and sequenced. The 6,783 bP pqq sequence had six open reading frames (from A to F) and showed 50-95％ homology to pqq genes from other bacteria. The E. coli strain expressing the pqq genes solubilized phosphate from hydroxyapatite after a pH drop to 4.0, which paralleled in time the secretion of gluconic acid. To study the role of PQQ in biocontrol traits of E. intermedium, PQQ mutants of 60-2G were constructed by marker exchangee mutagenesis. The PQQ mutants of E. intermedium were lost activities of solubilizing phosphate, growth inhibition of phytopathogenic fungi, and plant growth promotion. These findings suggest that PQQ plays an important role, possibly activation of certain enzymes, in several beneficial bacterial traits of E. intermedium by as yet an unknown mechanism.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.5
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• pp.342-347
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• 2008

Phosphate soubilized by microbes can be easily absorbed by plant as the element diffuses into soil solution. The microbes related to phosphate solubilizing activity are affected by the soil amendments such as rice straw compost, and lime. This study was performed to evaluate the effect of amendments to phosphate solubilizer in rice paddy soils. Available phosphate concentration was increased with the ratio of phosphate-solubilizing bacteria to aerobic bacteria in the rice paddy soils. The ratio was high in the plots applied with lime, silicate, and rice straw compost. Phosphate-solubilizing bacteria isolated from the soil were Aquasipirillum, Arthrobacter, Bacillus, Flavobacterium, Micrococcus and Micromonospora, Pseudomonas species. The highest dominant bacterial species was Pseudomonas, and Bacillus was followed.

• Journal of Microbiology and Biotechnology
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• v.18 no.4
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• pp.773-777
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• 2008

Phosphate solubilizing bacteria (PSB) were isolated from the rhizosphere of Chinese cabbage and screened on the basis of their solubilization of inorganic tricalcium phosphate in liquid cultures. Ten strains that had higher solubilization potential were selected, and they also produced indole-3-acetic acid, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and siderophores. The strains were identified to be members of Pseudomonas, by 16S rDNA sequence analysis. Seed bacterization with PSB strains increased the root elongation and biomass of Chinese cabbage in seedling culture, although they had no effect on phosphorus uptake of plants. The plant growth promotion by PSB in this study could be due to the production of phytohormones or mechanisms other than phosphate solubilization, since they had no effect on P nutrition.