The mechanism of phosphate solubilizing of Pseudomonas sp. TC952 and its solubilizing process on TC removal

Antibiotics undergo a series of complex transport and transformation route after entering the environment; however, there is scarce information about the effects of the bacterial phosphate-solubilizing process on tetracycline (TC) transformation. In this study, Pseudomonas sp. TC952 was identified as phosphate-solubilizing bacterium with high phosphate-solubilizing ability even under TC stress; it could solubilize maximum phosphate with a production of 400 mg/L soluble phosphate in 2 days. TC did not affect phosphate solubilizing in a short time incubation, but slightly promoted in a long incubation time. TC was adsorbed by inorganic phosphate with high efficiency of 53.09% within 1 day. Four tetracycline antibiotic resistance and sixteen inorganic phosphate-solubilizing-related genes were identified in the genome, which revealed the phosphate-solubilizing mechanism was that strain TC952 secrete organic acid to resolve inorganic phosphate and also secrete siderophore to chelate inorganic phosphate. So, during the inorganic phosphate-solubilizing process of strain TC952, TC was de-adsorbed from inorganic phosphate, and the solution was acidified into pH 4.3 through secreting organic acid to dissolve inorganic phosphorus, which resulted in Ca²⁺ and PO₄^3- releasing into the solution. Finally, the acidic condition and PO₄^3- enhanced TC hydrolysis. The mechanism of phosphate-solubilizing process on TC removal and genome analysis provides us new insight of the TC migration and transformation route in the environment.