title: Mechanism of insoluble phosphate solubilization by Pseudomonas fluorescens RAF15 isolated from ginseng rhizosphere and its plant growth-promoting activities.
abstract: OBJECTIVE
  To investigate the mechanism of insoluble phosphate (P) solubilization and plant growth-promoting activity by Pseudomonas fluorescens RAF15.
  
  
  RESULTS
  We investigated the ability of Ps. fluorescens RAF15 to solubilize insoluble P via two possible mechanisms: proton excretion by ammonium assimilation and organic acid production. There were no clear differences in pH and P solubilization between glucose-ammonium and glucose-nitrate media. P solubilization was significantly promoted with glucose compared to fructose. Regardless of nitrogen sources used, Ps. fluorescens RAF15 solubilized little insoluble P with fructose. High performance liquid chromatography analysis showed that Ps. fluorescens RAF15 produced mainly gluconic and tartaric acids with small amounts of 2-ketogluconic, formic and acetic acids. During the culture, the pH was reduced with increase in gluconic acid concentration and was inversely correlated with soluble P concentration. Ps. fluorescens RAF1 showed the properties related to plant growth promotion: pectinase, protease, lipase, siderophore, hydrogen cyanide, and indoleacetic acid.
  
  
  CONCLUSIONS
  This study indicated that the P solubility was directly correlated with the organic acids produced.
  
  
  CONCLUSIONS
  Pseudomonas fluorescens RAF15 possessed different traits related to plant growth promotion. Therefore, Ps. fluorescens RAF15 could be a potential candidate for the development of biofertilizer or biocontrol agent.
authors.affiliation: Department of Life Science and Environmental Biochemistry, Pusan National University, Miryang, Korea.
authors.forename: K-H
authors.initials: KH
authors.lastname: Park
authors.forename: C-Y
authors.initials: CY
authors.lastname: Lee
authors.forename: H-J
authors.initials: HJ
authors.lastname: Son
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D005561:Formates / Q000378:metabolism; D005632:Fructose / Q000378:metabolism; D005942:Gluconates / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000378:metabolism; D005894:Panax / Q000254:growth & development / Q000382:microbiology*; D010710:Phosphates / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000382:microbiology*; D011551:Pseudomonas fluorescens / Q000302:isolation & purification / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012988:Soil Microbiology; D013644:Tartrates / Q000378:metabolism
chemical_list: D003470:Culture Media; D005561:Formates; D005942:Gluconates; D009566:Nitrates; D010710:Phosphates; D010937:Plant Growth Regulators; D000644:Quaternary Ammonium Compounds; D013644:Tartrates; C030544:formic acid; C008229:2-ketogluconate; D005632:Fructose; D005947:Glucose; D019342:Acetic Acid; C030691:gluconic acid; C029768:tartaric acid