Antimony-oxidizing bacteria alleviate Sb stress in Arabidopsis by attenuating Sb toxicity and reducing Sb uptake

Abstract

Antimony (Sb)-oxidizing bacteria play an important role in Sb biogeochemical cycle in soil, but the benefits of microbial oxidation for plants have not been well documented. The aim of this study was to explore the contribution of Sb(III)-oxidizing bacteria to alleviate the Sb toxicity in plants. The plant growth-promoting (PGP) characteristics of Sb(III)-oxidizing bacterium Bacillus sp. S3 and the effects of bacterial inoculation on Arabidopsis plants were evaluated under controlled and Sb stressed conditions. Indole acetic acid (IAA) production and 1-aminocyclopropane-1-carboxylate-deaminase (ACC-deaminase) activity were the only two PGP strategies that Bacillus sp. S3 possessed, despite the production level of IAA and the activity of ACC deaminase sharply decreased under Sb stress. Bacillus sp. S3 inoculation significantly increased the plant biomass and chlorophyll content, alleviated the peroxidation of membrane lipids, decreased the activities of the antioxidant enzymes, and reduced the transcription of Sb transporters and reactive oxygen species (ROS)-related enzymes in Arabidopsis. Noteworthily, inoculation of Bacillus sp. S3 not only significantly decreased the Sb accumulation but also reduced the percentage of Sb(III) of total Sb in Arabidopsis. This study indicates that the Sb(III)-oxidizing strain of Bacillus sp. S3 is a promising inoculant used for bacteria-assisted phytoremediation on Sb-contaminated sites.