EVALUATION OF PHOSPHATE SOLUBILIZING BACTERIA ACTIVITY UNDER PHOSPHATE STARVATION

CASTAGNO, LUIS NAZARENO; ESTRELLA, MARÍA JULIA; RUIZ, OSCAR ADOLFO.

Tucumán. Argentina

Congreso; XLV Reunión Anual SAIB; 2009

SAIB

Mineral phosphate solubilization is an important plant growth-promoting ability via which phosphate (P) solubilizing bacteria (PSB) have found extensive applications as inoculants. The P solubilizing ability of bacteria is attributed to the secretion of organic acids, and the best characterized mechanism of P solubilization involves secretion of gluconic acid, which is produced by direct extracellular oxidation of glucose by a glucose dehydrogenase (GDH). The aims of this work were isolate and characterize PSB from the rizosphere of Lotus tenuis. All the isolates were characterized by antibiotic resistance and 16S rRNA gene sequencing. The analysis of this gene showed that isolates grouped with the genus Erwinia, Pantoea and Pseudomonas. One isolate related with Pantoea ananatis was selected for analysis of GDH activity, based on its high capacity of P-solubilization and L. tenuis growth promotion in “in vitro” assays. GDH activity was measured in cells grown with Ca3(PO4)2 as the insoluble P source and different levels of soluble P. The activity of GDH was increased 4-fold by starvation of soluble P and it was not repressed by the presence of high levels of soluble P. These preliminary results suggest that the P solubilizing ability of this isolate occurs due to the release of organic acids produced by glucose oxidation via GDH activity, as has been reported for other microorganisms.