Abstract

Maize rhizospheric soils in Mali were analysed for their content in 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) 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 mg P/g TPR on 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 produced organic acids were lactic acid, gluconic acid, oxalic acid and succinic acid. The two enzymes were Phosphatase acid and Pyrophosphatase. Their Activities ranged from 0.75 µg p-Nitrophenol/hour to 5.94 µg p-Nitrophenol/hour and 22.64µg PO₄^3- /hour to 45.50 µg PO₄^3- /hour, respectively.

Key words: Phosphate rock, solubilization, bacteria strains, Bacillus subtilis, rhizosphere, maize, PGPR, 16S rDNA, acid phosphatase and pyrophosphatase.