Isolation of the inorganic phosphorus-solubilizing bacteria Lysinibacillus sphaericus and assessing its role in promoting rice growth.

Soluble phosphorus scarcity severely limits plant growth and crop yield. In this study, a strain of inorganic phosphorus-solubilizing bacteria, Lysinibacillus sphaericus, was isolated from rice rhizosphere soil. The available phosphorus content in liquid inorganic phosphorus identification medium and in L. sphaericus-inoculated soil increased from 204.28 mg/L to 1124.68 mg/L and from 4.75 mg/kg to 7.04 mg/kg, respectively. The pH decreased significantly from 6.87 to 6.14. Incubation with L. sphaericus significantly increased malic and succinic acid content in the liquid inorganic phosphorus identification medium and increased acid phosphatase and alkaline phosphatase activity in the soil. Inoculation with L. sphaericus significantly increased rice growth, chlorophyll a/b content, and photosynthesis by increasing the soluble phosphorus content in the rice rhizosphere soil under phosphorus-deficient conditions. Further analysis revealed that L. sphaericus improved soil phosphorus release by decreasing soil pH and promoting acid phosphatase and alkaline phosphatase activity. This study supports the production of microbial fertilizers to improve rice yield in phosphorus-deficient conditions.

[Effect of progesterone on high mobility group Box-1 protein-induced interleukin-6 release by human umbilic vein endothelial cells].

OBJECTIVE: To study the effect of progesterone on interleukin-6 (IL-6) release from human umbilic vein endothelial cells (HUVECs) induced by high mobility group box-1 protein (HMGB1). METHOD: The recombinant expression plasmid pET14b-HMGB1 was constructed and transformed into competent E.coli BL21 cells to obtain HMGB1 protein, which was purified with chromatography on Ni-NTA Sepharose column. Cultured HUVECs were treated with purified HMGB1 protein alone at the concentrations 0, 10, 100, 500, and 1000 ng/ml, progesterone alone at the concentrations of 0, 0.1, 1, 10, 100 mmol/L, or with both HMGB1 protein (500 ng/ml) and progesterone at the terminal concentrations of 0, 0.1, 1, 10, and 100 mmol/L. Twenty-four hours later, the supernatant of the cell culture medium was collected to detect the levels of IL-6 using enzyme-linked immunosorbent assay (ELISA). RESULTS: The IL-6 levels in HUVEC culture medium was slightly decreased after treatment with low-concentration HMGB1 but increased obviously following treatment with high-concentration HMGB1, and these effects could be dose-dependently inhibited by progesterone. Progesterone alone did not result in any noticeable changes of IL-6 levels in the cell culture medium. CONCLUSIONS: Progesterone can dose-dependently inhibit HMGB1-induced IL-6 release from HUVECs, suggesting the protective role of progesterone in endotoxemia.