Isolation and characterisation of phosphate-solubilising bacteria from serpentine soils in Yen Bai Province

Abstract

Phosphate-solubilising bacteria (PSB) contribute to plant phosphorus nutrition by transforming insoluble phosphates into bioavailable forms. In our work, PSB were isolated from serpentine soils in Yen Bai Province, Vietnam—an environment typified by low nutrient availability and elevated metal content. Forty-two bacterial isolates with phosphate-solubilising traits were screened in the NBRIP medium. Among them, strain VW132 demonstrated the highest solubilisation capacity and was taxonomically identified as Burkholderia sp. via 16S rRNA gene analysis. Strain VW132 reached maximum phosphate solubilisation of 359 mg/L when cultivated under optimised conditions, i.e, ammonium sulfate and glucose as nitrogen and carbon sources, 1% NaCl, and pH 7. However, phosphate solubilisation markedly declined at NaCl concentrations exceeding 1%, suggesting reduced salt tolerance. The relationship between soluble phosphate concentration and biofilm development was also investigated. Results show enhanced biofilm formation with increasing levels of K2HPO4, indicating a phosphate-dependent biofilm response.