Abstract

In this study, four inorganic phosphate-solubilizing bacteria (PSB), that is, PSB1, PSB2, PSB14, and PSB16, were isolated from horse bean soil sampled from a farm at Southwest University, China. We evaluated the toxic effects of artemisinin (0, 24, and 48 mg L^–1) on PSB. To assess the antibacterial activity on PSB, the growth curves were modeled for different concentrations of artemisinin in liquid culture media. The ratio ofglucose or saccharose utilization as a carbon source was measured. To further investigate the effect of artemisinin on the phosphate (P) release ability of PSB, P, organic acid, and pH in PSB culture solutions were determined. Artemisinin severely affected thegrowth and propagation of PSB. The amounts and carbon source utilization ratio of PSB with 48 mg L^–1 artemisinin were significantly lower than with 0 mg L^–1 after 6 h. The capacity of PSB for tricalcium phosphate (TCP) P solubilization was severely affected by artemisinin, the total P released by PSB1, PSB2, PSB14 and PSB16 inoculated with 48 mg L^–1 artemisinin decreased by 31.45, 38.19, 6.73, and 12.41%, respectively, relative to 0 mg L^–1. The major organic acids secreted by PSB (oxalic acid and citric acid) decreased with increasing artemisinin concentrations, with consequent effects on pH. It is concluded that high concentration artemisinin inhibits the growth and organic acid secretion of PSB, with further effects on P-solubilization, which is significant when evaluating its ecotoxicity.

Key words: Artemisinin, carbon source utilization ratio, inorganic phosphate-solubilizing bacteria, growth curves, organic acids, toxic effects