isolation and characterization of phosphate solubilising bacteria from pb contaminated and p-amended soils

1. Isolation and characterization of phosphate solubilising bacteria from Pb contaminated and P-amended soils I am Jin-hee Park. Today I will present about isolation and characterization of phosphate solubilising bacteria from Pb contaminated and P-amended soils. My principle supervisor is Prof. Nanthi Bolan, and my associate supervisors are prof. Ravi Naidu and Megharaj Mallavarapu.I am Jin-hee Park. Today I will present about isolation and characterization of phosphate solubilising bacteria from Pb contaminated and P-amended soils. My principle supervisor is Prof. Nanthi Bolan, and my associate supervisors are prof. Ravi Naidu and Megharaj Mallavarapu.

2. This is outline of my talk. Firstly, I will introduce concept of lead immobilisation and P solubilisation. Then, milestones of my study, methods used in this project, results and discussion and conclusions.This is outline of my talk. Firstly, I will introduce concept of lead immobilisation and P solubilisation. Then, milestones of my study, methods used in this project, results and discussion and conclusions.

3. These are my milestones. These are my milestones.

4. As everybody knows lead is toxic element, but lead toxicity can be mitigated by reducing its bioavailability using immobilizing agent such as phosphate compounds. Phosphate compounds are very effective in the precipitation of Pb. The solubility product constants of Pb-phosphate compound is very low. As everybody knows lead is toxic element, but lead toxicity can be mitigated by reducing its bioavailability using immobilizing agent such as phosphate compounds. Phosphate compounds are very effective in the precipitation of Pb. The solubility product constants of Pb-phosphate compound is very low.

5. Both soluble and insoluble P compounds have been used to immobile Pb, but soluble phospahte compounds can cause leaching of phosphorus and that can be also another contaminating source. Insoluble P compounds such as phosphate rocks can be used to immobilize Pb, but this is not easily solubilised, so need large amount of amendment. These compounds can be solubilised by phosphate solubilising bacteria. The activity of P solubilising bacteria is affected by enrichment of soil with P and Pb compounds.Both soluble and insoluble P compounds have been used to immobile Pb, but soluble phospahte compounds can cause leaching of phosphorus and that can be also another contaminating source. Insoluble P compounds such as phosphate rocks can be used to immobilize Pb, but this is not easily solubilised, so need large amount of amendment. These compounds can be solubilised by phosphate solubilising bacteria. The activity of P solubilising bacteria is affected by enrichment of soil with P and Pb compounds.

6. Overall objectives of my research are to examine the role of phosphate solubilising bacteria in the solubilisation of P in soils and to evaluate the potential value of rock phosphate in the immobilization of Pb through lead phosphate precipitation by phosphate solubilising bacteria. The specific objectives of this presentation are firstly to isolate and quantify phosphate solubilising bacteria in phosphate emended and Pb contaminated soils and secondly to examine their efficiency in solubilising insoluble phosphate compounds. Overall objectives of my research are to examine the role of phosphate solubilising bacteria in the solubilisation of P in soils and to evaluate the potential value of rock phosphate in the immobilization of Pb through lead phosphate precipitation by phosphate solubilising bacteria. The specific objectives of this presentation are firstly to isolate and quantify phosphate solubilising bacteria in phosphate emended and Pb contaminated soils and secondly to examine their efficiency in solubilising insoluble phosphate compounds.

7. Methods used for my experiment Plant available Phosphorus of soils was measured by Olsen P method and Bioavailable Pb was extracted with Calcium nitrate. Bacterial population (CFU) was calculated by typical plate counting method. National Botanical Research Institute's phosphate growth medium (NBRIP) medium including tricalcium phosphate were used for isolation of phsophate solubilising bacteria. Solubilised phosphate was measured following Murphy and Riley (1964) method. The phosphatise activity in the cultured filtrate was measured following Tabatabai (1969) method. Organic acids were analysed by Ion Chromatography.Methods used for my experiment Plant available Phosphorus of soils was measured by Olsen P method and Bioavailable Pb was extracted with Calcium nitrate. Bacterial population (CFU) was calculated by typical plate counting method. National Botanical Research Institute's phosphate growth medium (NBRIP) medium including tricalcium phosphate were used for isolation of phsophate solubilising bacteria. Solubilised phosphate was measured following Murphy and Riley (1964) method. The phosphatise activity in the cultured filtrate was measured following Tabatabai (1969) method. Organic acids were analysed by Ion Chromatography.

8. This table shows soils used for experiment. These four soils were taken from lead contaminated site in South Korea and Australia and have various bioavailble lead fractions. These four soils were taken from phosphate amended site in New Zealand. These soils have high Olsen P level. Kwon-Rae and Loganathan provided these soils. (?? 20 ??? ?? ?? ?? ??, ? PP? P ??? ??? ??, Pb ??? ??? ?????? ??)This table shows soils used for experiment. These four soils were taken from lead contaminated site in South Korea and Australia and have various bioavailble lead fractions. These four soils were taken from phosphate amended site in New Zealand. These soils have high Olsen P level. Kwon-Rae and Loganathan provided these soils. (?? 20 ??? ?? ?? ?? ??, ? PP? P ??? ??? ??, Pb ??? ??? ?????? ??)

9. This is diagram of isolating phosphate solubilising bacteria. Soil solution was diluted and spread on NBRIP medium and purified. Purified bacteria were precultured in NBRIP broth medium. 1 mL of this culture was transferred into 100 mL of same medium and incubated. After 2 weeks pH, phosphorus concentration, phosphatise activity and organic acid were analyzed. This is photo of bacteria. Bacteria solubilised insoluble tricalcium phosphate and made halo around colony.This is diagram of isolating phosphate solubilising bacteria. Soil solution was diluted and spread on NBRIP medium and purified. Purified bacteria were precultured in NBRIP broth medium. 1 mL of this culture was transferred into 100 mL of same medium and incubated. After 2 weeks pH, phosphorus concentration, phosphatise activity and organic acid were analyzed. This is photo of bacteria. Bacteria solubilised insoluble tricalcium phosphate and made halo around colony.

10. This graph shows relationship between Olsen P concentration and number of isolated phosphate solubilising bacteria. These bacteria were isolated from phosphorous ameded soils and these bacteria were isolated from Pb contaminated soils. Except this value olsen P and number of phosphate solubilising bacteria showed good correlation. This soil sample has high Olsen P concentration, but its lead concentration was also high so, growth of phosphate solubilising bacteria was inhibited.This graph shows relationship between Olsen P concentration and number of isolated phosphate solubilising bacteria. These bacteria were isolated from phosphorous ameded soils and these bacteria were isolated from Pb contaminated soils. Except this value olsen P and number of phosphate solubilising bacteria showed good correlation. This soil sample has high Olsen P concentration, but its lead concentration was also high so, growth of phosphate solubilising bacteria was inhibited.

11. This table shows concentration of solubilised phosphorus and organic acid and phosphatise activity. These bacterial strains were isolated from lead contaminated soils and These bacterial strains were isolated from phosphate compound amended soils. These bacterial strains solubilised upto 490 mg/L. I calculated correlation coefficient value between soulbilsed phosphorous concentration and these factors.This table shows concentration of solubilised phosphorus and organic acid and phosphatise activity. These bacterial strains were isolated from lead contaminated soils and These bacterial strains were isolated from phosphate compound amended soils. These bacterial strains solubilised upto 490 mg/L. I calculated correlation coefficient value between soulbilsed phosphorous concentration and these factors.

12. This graphs show correlation between organic acid concentration and pH and solubilised phosphorous concentraion. These were well correlated and this means phosphorous solubilisation mechanism by bacteria is pH reduction by production of organic acids.This graphs show correlation between organic acid concentration and pH and solubilised phosphorous concentraion. These were well correlated and this means phosphorous solubilisation mechanism by bacteria is pH reduction by production of organic acids.