Temporal shifts in the phosphate mobilising bacterial community reveal contrasting succession patterns in response to different phosphorus sources.

Background: Phosphate mobilising bacteria (PMB), such as phoD- and pqqC-harbouring bacteria, play a crucial role in mobilising insoluble phosphorus (P) in soil through the secretion of alkaline phosphatase and organic acids.

Objectives: To evaluate the succession pattern of PMB communities in response to different insoluble P sources.

Methods: Five P source treatments, including the addition of KHPO (PDP), FePO (FEP), Ca(PO) (TCP), lecithin (LEC), and a negative control, were established in the soil in a microcosmic system. Subsequently, phoD- and pqqC-harbouring bacterial communities were investigated by sequential sampling and high-throughput sequencing. In addition, PMB strains were isolated from these five treatments, and their phosphate mobilising activity was further analysed.

Results: The effect of the insoluble organic P source (LEC) on the succession of PMB communities consistently exceeded that of insoluble inorganic P (Pi) sources (FEP and TCP). A successively enhanced succession and a successively diminishing succession were observed in PMB communities in FEP and TCP, respectively. Furthermore, the soil AP content significantly increased with incubation time in LEC and FEP. Most of the variation in phoD- and pqqC-harbouring bacterial communities was explained by all P fractions, respectively, while Fe-P and stable organic P fractions determined the PMB communities. Insoluble Pi sources, particularly FEP, tended to enrich more high-performance PMB strains for Fe-P.

Conclusion: This study firstly reveals the dynamic response of PMB communities to different insoluble P sources at the community level in a short time scale and identifies key PMB taxa that respond to different insoluble P sources, particularly Fe-P. It is also the first to provide community evidence and a feasible method for obtaining high-performance PMB strains for Fe-P in subtropical acidic red soils through directed enrichment culture.