• Korean Journal of Microbiology
• /
• v.42 no.3
• /
• pp.223-229
• /
• 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
• /
• v.5 no.2
• /
• pp.61-68
• /
• 1967

In the process of the incorporation of orthophsphate into protein and other cell constituents, the role of inorganic polyphosphate and RNA-polyphosphate complex and the correlation between them were pursued by analyzing the contents of $^{32}P$ and total P in various fractions of Chlorella cells, which had been uniformly labeled with $^{32}P$ before the inoculation in a normal "cold" medium or P-free medium during the culture. The effects of ionizing radiation and various micronutritional-element deficiencies on the phosphate incorporation into, and biosynthesis of, protein and other introgenus compounds in the cells were also observed. When the uniformly $^{32}P$-labeled algae were grown in a normal "cold" medium the contents of $^{32}$ P in the fractions of protein, DNA and RNA-polyphosphate complex increased, but those in the fraction of acid-insoluble polyphosphate decreased. On the other hand, amount of $^{32}P$in the fraction of RNA was almost unchanged in spite of rapid increase of the total P. In the growing period of $^{32}P$-labeled algae in a P-free medium, amounts of $^{32}P$ in the fractions of DNA, protein and lipid increased, while those in the fractions of RNA-polyphosphate and inorganic polyphosphates decreased. When the algal cells were irradiated with about 70, 000r of gamma-rays before the inoculation in the medium, amounts of phosphate in the fractions of DNA, RNA, nucleotides and protein decreased during the culture, compared with those of the control. However, the phosphate content in the fraction of acid-insoluble polyphosphate of the irradiated cells increased than those of the control. In the growing period of the algae in a Mo-free, medium, amounts of acid-soluble total phosphate and nucleotides of the cells increased, while the amounts of residual protein and RNA decresed compared with those of the normal cells. Amounts of alkali-labile protein and phospholipid of the cells grown in a B-free medium decreased, whereas amount of phosphate in acid-soluble fraction increased compared with the control. In general, the contents of protein and RNA in each microelement deficient cells decreased more or less, compared with those in the normal cells.in the normal cells.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.7 no.4
• /
• pp.201-205
• /
• 2002

The growth conditions of Pantoea aggicmerans, a phosphate solubilizing organism, were studied In our laboratory to determine the optimal conditions. Pantoea aggionerans showed the highest growth rate at 30$\^{C}$, pH 7.0 and 2 vvm, after 50 h cultivation. A certain relationship between pH and phosphate concentration was evident when the glucose concentration in the me dium was changed. Increasing glucose concentration increased the pH buffer action of the broth. At glucose concentrations higher than the optimum concentration of 0.2 M, the cell growth was retarded. P. agglomerans consumed glucose as a substrate to produce organic acids which caused the pH decrease in the culture medium. The phosphate concentration in the medium was increased by the presence of the organic acids, which solubilized insoluble phosphates such as hydroxyapa-tite.

• 한국생물공학회:학술대회논문집
• /
• 2001.11a
• /
• pp.586-589
• /
• 2001

In this study, phosphate was produced through the solublization of hydroxyapatite and rock phosphate by Pantoea agglomerans, and it was examined the possibility of solublizing insoluble phosphate salt by immobilized P. agglomerans on Ca-alginate bead as support. 520mg/L of phosphate was solublized when P. agglomerans was cultured in HY meclium at $30^{\circ}C$, pH7, 100rpm, during 48hours culture. And solublized phosphate amount was 86.09mg/L when hydroxyapatite in the HY medium was exchanged to rock phosphate. In case of being used immobilized P. agglomerans. 740mg/L of phosphate was solublized in the HY medium, during 120hrs in the same condition. And 182mg/L of phosphate was solublized when rock phosphate was added instead of hydroxyapatite.

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

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

• 한국생물공학회:학술대회논문집
• /
• 2001.11a
• /
• pp.414-417
• /
• 2001

This research was compared the amount of phosphate solublized by Pantoea agglomerans which can solublize the insoluble phosphate salt hydroxyapatite with the phosphate produced by being treated with various acids. When P. agglomerans grows in the BY medium containing potassium dihydrogenphosphate of phosphate source without hydroxyapatite, it consumed 361mg/L phosphate, during 72hours cultivation. When 4% hydroxapatite was treated with 0.01N citric acid and oxalic aicd, the amount of solublized phosphate was 702mg/L and 537mg/L more than that by P.agglomerans. The maximum amount of solublized phosphate by P. agglomerans was 465mg/L after 48 hours cultivation.

• Korean Journal of Soil Science and Fertilizer
• /
• v.45 no.6
• /
• pp.998-1003
• /
• 2012

Pantoea agglomerans DSM3493 was isolated from green house soils collected from Chungchugnam-do province, Gongju-Gun area in South Korea and phosphate solubilization and organic acid production of the strain were assessed using three types of insoluble phosphate sources (Ca phosphate, Fe phosphate and Al phosphate) under three different pH conditions (7, 8 and 9). The highest Ca phosphate solubilization ($651{\mu}g\;mL^{-1}$) was recorded at pH 7 followed by pH 8 and 9 (428 and $424{\mu}g\;mL^{-1}$ respectively). The solubilization rate was found to be 80.4, 98.1 and $88.7{\mu}g\;mL^{-1}$ (for Fe phosphate containing medium) and 9.3, 12.1 and $29.8{\mu}g\;mL^{-1}$ (for the Al phosphate containing medium) respectively at pH 7, 8 and 9. Though increasing pH of the medium caused reduction in the rate of solubilization of Ca phosphate, solubilization of Fe and Al phosphates enhanced with increasing pH. By contrast, the highest amount of organic acid was produced with Ca phosphate while the lowest was recorded with the presence of Al phosphate. Among the organic acids, gluconic acid production was found to be the highest, followed by oxalic acid and citric acid regardless the source of phosphate. Results can thus be concluded that the production of organic acids appears to play a significant role in the inorganic phosphate solubilization.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2003.10a
• /
• pp.94.2-95
• /
• 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 Agricultural Science
• /
• v.49 no.3
• /
• pp.463-481
• /
• 2022

Phosphorous (P) is considered to be one of the key essential elements demanded by crop plants. Approximately 70 - 90% of phosphatic fertilizers applied to crops are fixed in soil as Ca, Fe, and Al metal cations, which are insoluble and thus not readily available for plant uptake. Therefore, most soils are deficient in plant available P. This is usually rectified by applying phosphate fertilizers continuously, although this is not economically viable or environmentally acceptable. The present paper reviews the mechanisms involved with phosphate solubilization and mineralization by phosphate solubilizing microorganisms (PSMs) with the associated factors that determine the success. PSMs are effectively involved in mediating the bioavailability of soil P. Their contribution includes mineralization of organic P solubilization of inorganic P minerals, and storing sizable amounts of P in biomass through different mechanisms such as the production of organic and inorganic acids, H₂S, siderophores, exopolysaccharides, and production of enzymes such as phosphatases, phytase, and phosphonatases/C-P lyases, which are capable of chelating the metal ions, forming complexes, and making plant available P. PSMs manifest a wide range of metabolic functions in different environments, resulting in significantly higher plant growth, enhanced soil properties, and increased biological activities. Therefore, development of bio-inoculants with efficient novel PSM strains and further investigations on exploring such strains from diverse ecological niches with multifunctional plant-growth-promoting traits are needed.