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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOGEOCHEMICAL PROCESSES AND SOIL MANAGEMENT IMPACTS ON SOIL EROSION, SOIL/AIR/WATER QUALITY, AND GREENHOUSE GAS EMISSIONS

Location: National Soil Erosion Research Lab

Title: Characterization of six phosphate-dissolving bacteria isolated from rhizospheric soils in Mali

Authors
item Traore, Lamine -
item Nakatsu, Cindy -
item DE Leon, Allysa -
item Stott, Diane

Submitted to: African Journal of Microbiology Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 19, 2013
Publication Date: July 12, 2013
Citation: Traore, L., Nakatsu, C.H., De Leon, A., Stott, D.E. 2013. Characterization of six phosphate-dissolving bacteria isolated from rhizospheric soils in Mali. African Journal of Microbiology Research. 7(28):3641-3650.

Interpretive Summary: In many African countries, including Mali, the primary source of P-fertilizer is rock phosphate, which is notoriously insoluble. It has been noted that certain species and strains of bacteria are capable of solubilizing rock phosphate and producing plant available P. In this study, six bacterial strains capable of solubilizing rock phosphate produced from the quarry in Tilemsi region of Mali. Using molecular techniques, the bacteria were all identified as strains of Bacillus subtilis, a common soil organism, and the production of organic acids involved in the solubilization process were identified. In addition, the production of some key phosphorus enzymes was verified. The impact of this work is the isolation and identification of rock phosphate solubilizing bacteria that can ultimately be used as seed inoculants to increase P availability to crops grown in P-deficient soils in Africa and elsewhere.

Technical Abstract: Maize rhizospheric soils in Mali were analyzed for concentrations of microorganisms capable of dissolving phosphate rock and producing plant growth substances. Six bacteria were isolated and found to have the capacity to dissolve /solubilize the Tilemsi phosphate rock (TPR) available in Mali by producing low molecular weight organic acids and phosphorus cycle enzymes. The bacterial isolates had an average of TPR solubilization efficiency of 195% on solid medium and 282 g P/kg TPR in liquid medium. The aim of this work was to identify these microorganisms using molecular techniques as well as determining the nature of the produced organic acids and the level of P-related enzyme activity. The 16S rDNA sequencing indicates that all the bacteria were Bacillus subtilis and the organic acids produced were lactic, gluconic, oxalic and succinic acids. The two enzymes that were tested for were acid phosphatase and pyrophosphatase. Their activities ranged from 0.75 to 5.94 mg p-nitrophenol released/hour/kg TPR and 22.6 to 45.5 µg PO4 released/ hour /kg TPR, respectively. The impact of this work is the isolation and identification of TPR solubilizing bacteria that can ultimately be used as seed inoculants to increase P availability to crops grown in P-deficient soils. Rock phosphate is the only domestic supply of P for use in fertilizers.

Last Modified: 12/21/2014
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