Genomic insights into organic acid production and plant growth promotion by different species of phosphate-solubilizing bacteria.

Bacteria can solubilize phosphorus (P) through the secretion of low-molecular-weight organic acids and acidification. However, the genes involved in the production of these organic acids are poorly understood. The objectives of this study were to verify the calcium phosphate solubilization and the production of low-molecular-weight organic acids by diverse genera of phosphate solubilizing bacterial strains (PSBS); to identify the genes related to the synthesis of the organic acids in the genomes of these strains and; to evaluate growth and nutrient accumulation of maize plants inoculated with PSBS and fertilized with Bayóvar rock phosphate. Genomic DNA was extracted for strain identification and annotation of genes related to the organic acids production. A greenhouse experiment was performed with five strains plus 150 mg dm^- 3 P₂O₅ as Bayóvar rock phosphate (BRP) to assess phosphate solubilization contribution to maize growth and nutrition. Paraburkholderia fungorum UFLA 04-21 and Pseudomonas anuradhapurensis UFPI B5-8A solubilized over 60% of Ca phosphate and produced high amounts of citric/maleic and gluconic acids in vitro, respectively. Eleven organic acids were identified in total, although not all strains produced all acids. Besides, enzymes related to the organic acids production were found in all bacterial genomes. Plants inoculated with strains UFPI B5-6 (Enterobacter bugandensis), UFPI B5-8A, and UFLA 03-10 (Paenibacillus peoriae) accumulated more biomass than the plants fertilized with BRP only. Strains UFLA 03-10 and UFPI B5-8A increased the accumulation of most macronutrients, including P. Collectively, the results show that PSBS can increase maize growth and nutrient accumulation based on Bayóvar rock phosphate fertilization.