Staphylococcus hominis YJILJH and Staphylococcus epidermidis YJ101 promote the growth of white clover (Trifolium repens L.) by increasing available phosphorus

Abstract

Phosphorus is critical for the regulation of numerous metabolic processes in plants, and so understanding the mechanisms by which plants acquire phosphorus is important. Phosphate solubilizing bacteria (PSB) are thought to promote the uptake of phosphorus by plants. The effects of PSB YJILJH and YJ101 strains on the growth of white clover (Trifolium repens L.) were investigated through the production of the plant hormone IAA and the change of available phosphorus content in the soil. Two strains of YJILJH and YJ101 were selected from the rhizosphere soil of white clover among rows of apple orchards. Combined with 16S rDNA and next-generation sequencing (NGS), the strains were identified as Staphylococcus hominis and Staphylococcus epidermidis, respectively. The two strains had strong phosphate solubilizing ability, and had solubilization index (SI) values of 4.39 and 3.95, respectively. The dissolved amounts of soy lecithin were 351.2 and 387.3 mg/L in liquid medium, respectively. The amount of Ca3(PO4)2 dissolved reached 506.3 and 789.8 mg/L, respectively. The pot experiment showed that the biomass of white clover after adding the two strains increased by 21.17% and 36.49%, the total phosphorus (TP) content increased by 28.87% and 30.41%, and the soil available phosphorus (AP) content increased by 86.63% and 47.16%, respectively. This study also found that both strains can produce IAA content reaching 55.95 and 54.33 pmol / L in 72 h. In regard to relative gene expression, trpD and trpA genes were expressed in the different treatments, while ipdC was only expressed in Luria-Bertani broth (LB broth) and NBRIP media (+ soy lecithin). It is speculated that the pathway of IAA synthesis by both strains may be related to the tryptophan side chain pathway and the indole-3-pyruvate pathway. The IAA produced by the two bacteria strains is an important reason to promote the growth of white clover and participate in the process of reducing the environmental pH of the growth medium.