Arsenite [As(III)] is the predominant arsenic (As) species in flooded paddy soil, As(III) bioaccumulation in rice grains has been identified as a major problem in many countries of the world. Arsenite oxidation can be accelerated by bacterial catalysis, but the effects of bacterial catalysis on accelerated As(III) oxidation in flooded paddy soil are poorly understood. Herein we investigated how an arsenite-oxidizing bacterium GD03, namely Achromobacter xylosoxidans, influences As(III) oxidation in flooded paddy soil, As(III) toxicity and translocation from paddy soil to rice grain. Rice seedlings of Guang You Ming 118 (GYM) at four-leaf-stage was inoculated with different inoculation percent of GD03 into potting soil added by 100 mg/kg As(III) to investigate the effect of GD03 on accelerated As(III) oxidation in flooded paddy soil and its effects on arsenic toxicity and translocation from paddy soil to rice grain. The results showed that GD03 significantly (p < 0.01) accelerated the oxidation of As(III) in soil solution of GYM indica cultivar stressed by As(III) after 1d’s inoculation. GD03 increased Eh value of soil solution the most at booting stage of indica cultivar GYM stressed by As(III). As for different percent of GD03 inoculation, the treatment with 7.2×10⁹ CFU GD03 /kg soil had the highest Eh value and the lowest As(III) concentration in soil solution of indica cultivar GYM stressed by As(III) from 1 d’s inoculation till Maturation Stage and showed the best subdued As(III) toxicity at its each growth stage. The inoculation of GD03 led to 59% to 96% increase in rice grain yield, as well as 35% to 57% of As(III) concentration decrease in rice grain. Therefore, the accelerated oxidation for As(III) in flooded paddy soil was a promising method to mitigate As(III) induced human health risk.

Funding support: Natural Science Foundation of China (grant numbers 21677033) and Fujian Provincial Project of Science and Technology (grant numbers 2017Y0002)