Bacterial community response in ginseng rhizosphere soil after Pseudomonas P1 inoculation integrating intracellular non-targeted metabolomics analysis

To overcome the problems associated with insufficient available phosphorus in ginseng-growing soil, non-targeted metabolomics and high-throughput sequencing were adopted in this study to reveal the intracellular metabolites of Pseudomonas P1 and their effects on the soil bacterial community structure in ginseng-growing soil after Pseudomonas P1 inoculation. The results showed that although the P1 colony number was 4.68×107 cfu/mL after 32 h of cultivation, the available phosphorus stabilized at 24 h. Furthermore, 351 differential metabolites (162 and 189 in the positive and negative ion models, respectively) were screened from the eight P1 cultivation groups. Venn diagrams revealed more common metabolites in the negative ion model (45 metabolites) than in the positive ion model (17 metabolites). Organic acids and derivatives, at 23.53% and 15.56% in the positive- and negative-ion models, respectively, may be the dominant metabolites involved in phosphate dissolution. Although P1 inoculation had little effect on bacterial diversity, significant changes in bacterial phyla composition were identified between P10 and CK. Specifically, the relative abundance of Pseudomonadales in P10 was higher than that in CK (P < 0.05). Canonical discriminant analyses and correlation analysis showed that the shifts in bacterial community composition and structure were closely related to physicochemical factors, such as available phosphate, total potassium, NH4+-N, NO3--N, and pH. Our results suggest that P1 intracellular metabolites contain several organic acids, which reduce soil pH after inoculation, affect the supply of available phosphate, and change the composition of the microbial community structure and direction of cluster evolution.