Phosphorus Dissolving Aspects Of Phosphobacteria YM3-2S And Phosphorus Dissolving Gene Cloning

Phosphorus is one of the most important essential elements for plant growth, andemploying phosphorus fertilizer is a very crucial management to increase crop yields;on the other hand, overcommitment of phosphorus fertilizer in agriculture broughtmany environmental problems. Usually, insoluble phosphate in soil can be dissolvedby phosphorus solublizing microorganisms, and absorbed by plant, which canincrease the utilizing rate of phosphorus fertilizer, and decrease absorption andimmobility of phosphate in soil, and avoid environmental pollution caused byslathering phosphorus fertilizer. Hence, from ecological and social point of view, it isof great important for agricultural sustainable development that screening highefficiency phosphate-solublizing microbial strains as inoculant to manufacturebiofertilizer, and is helpful to reduce dosage quantity,In this study, phosphorus solublizing bacteria was isolated from soil samplescollected from 7 different sites in Sichuan Province, then identified by physiologicalanalysis, and the growth and phosphate-solublizing characteristics was determined,the results was as follow:1. One inorganic phosphate-solublizing bacterium, named YM3-2S, was isolatedfrom soil sample and purified by streak method. The results of bio-physiologicalaspects and 16S rDNA sequence analysis showed that strain YM3-2S belonged toBurkholderia cepacia in taxonomic position.2. Results of growth aspects and phosphate-solublizing ability revealed thatYM3-2S had short generation time (G=25 min), and grew rapidly, and had good acidproducing ability. YM3-2S had high phosphate-solublizing ability, and could transferphosphorite into valid phosphorus, and the concentration of phosphorus reached 40.96mg/L in the liquid ferment culture; the quantity of phosphorus in liquid cultureincreased with solution pH decreasing, and the phosphate-solublizing rate wascorrelated with its acid-producing ability tightly.3. Fungus repressing experiments showed that YM3-2S could restrain the growth ofabout 10 pathogenic fungal strains, such as Helminthosporium turcicum,Bipolaris maydis, etc.4. The ferment product was analyzed by paper chromatography method, and theresults showed that there was only one kind of organic acid produced by YM3-2S, andthe exact component needed to be analyzed further. 5. Different treatments in potted plant experiments inoculated YM3-2S as effectivestrain was done, the results suggested that the concentration of valid phosphorus intested soils changed as the follwing order: CK＞CK+NK＞CK+phosphoritemineral powder+NK＞CK+YM3-2S+NK＞CK+NK+YM3-2S+phosphoritemineral powder+compost. The results suggested that YM3-2S could dissolve theinvalid phosphorite, and changed phosphorite into valid phosphorus, which washelpful to enhance phosphorus validity in soil, and improve plant phosphorusnutrition.6. Phosphate-solublizing gene gabY was cloned and a positive clone pD6034 wasgot successfully. The gabY gene was sequenced and compared with those sequencespublished in GeneBank, the results showed that the homology between D6034 andU10242 was 97.49%. Product predicted by D6034 sequences showed that D6034coded a single peptide with 28 amino acid, which suggest that product coded by gabYgene excreted out the cell. Checked by SDS-PAGE, the expression product of D6034was a 14kD protein.