• 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.

• 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.

• 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.

• 한국생태학회:학술대회논문집
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• 2002.08a
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• pp.93-100
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• 2002

Dynamics of certain $N_2$fixing bacteria such as Rhizobium, Azospirillum and Azotobactor, nodule number in dominant legume, Atylosia trinervia, P-solubilizing bacteria, actinomycetes and fungi were studied in unburned and burned site of natural grassland, southern India. Population of $N_2$- fixing bacteria, P-solubilizing bacteria, fungi and nodule number in legume increased significantly in burned sites. On the other hand, the actinomycetes population remained unchanged. Thirty six species of fungi with tricalcium phosphate solubilizing ability were recorded. The most efficient P-solubilizing fungi recognised in the soils of the study sites are Absidia ramosa, Gongronella butlerii, Mortieralla spinosa, Mucor racemosus, Rhizopus nigricans, R. stolonifer, R. oryzae, Aspergillus fumigatus, A. nidulans, A. niger Theilavia terricola and Cheatomium lunasporium.

• The Korean Journal of Ecology
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• v.25 no.4
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• pp.227-234
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• 2002

Dynamics of certain $N_2$ fixing bacteria such as Rhizobium, Azospirillum and Azotobactor, nodule number in dominant legume, Atylosia trinervia, P-solubilizing bacteria, actinomycetes and fungi were studied in unburned and burned site of natural grassland, southern India. Population of $N_2$ - fixing bacteria, P-solubilizing bacteria, fungi and nodule number in legume increased significantly in burned sites. On the other hand, the actino-mycetes population remained unchanged. Thirty six species of fungi with tricalcium phosphate solubilizing ability were recorded. The most efficient P-solubilizing fungi recognised in the soils of the study sites are Absidia ramosa, Gongronella butlerii, Mortieralla spinosa, Mucor racemosus, Rhizopus nigricans, R. stolonifer, R. oryzae, Aspergillus fumigatus, A. nidulans, A. niger, Theilavia terricola and Cheatomium lunasporium.

• The Journal of Natural Sciences
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• v.12 no.1
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• pp.69-79
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• 2002

850 strains of phosphate-solubilizing bacteria were isolated from soil of Chung-nam and Daejeon region using 0.5% calcium phosphate containing medium. The HS-2 strain with the highest rock phosphate-solubilizing activity was selected and identified as Azotobacter sp. HS-2 based on the microbiological characteristics. The optimum culture temperature and initial pH of medium for solubilization of rock phosphate were $30^{\circ}C$ and pH 6.0-7.0, respectively. Addition of oxalic acid(0.5M) into the PDB-rock phosphate medium increased 50% solubilization of rock phosphate.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.169-176
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• 2012

Among the major nutrients, phosphorus is by far the least mobile and available to plants in most soil conditions. A large portion of soluble inorganic phosphate applied to soil in the form of phosphate fertilizers is immobilized rapidly and becomes unavailable to plants. To improve the plant growth and yield and to minimize P loss from soils, the ability of a few soil microorganisms converting insoluble forms into soluble forms for phosphorus is an important trait in several plant growth-promoting microorganisms belonging to the genera Bacillus and Pseudomonas and the fungi belonging to the genera Penicillium and Aspergillus in managing soil phosphorus. The principal mechanism of solubilization of mineral phosphate by phosphate solubilizing bacteria (PSB) is the release of low molecular weight organic acids such as formic, acetic, propionic, lactic, glycolic, fumaric, and succinic acids and acidic phosphatases like phytase synthesized by soil microorganisms in soil. Hydroxyl and carboxyl groups from the organic acids can chelate the cations bound to phosphate, thereby converting it into soluble forms.

• 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.

• 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.