Background and aims The oxidation of antimony (Sb) by rhizosphere microorganisms is regarded as a strategy to mitigate the phytotoxicity of Sb(III). This study aims to isolate a highly efficient Sb-oxidizing bacterium (named HC02) from Sb-contaminated soil and to investigate the bacterium's impact on the growth of Brassica napus under practical soil conditions. Methods The oxidative properties of HC02 were assessed in LB liquid medium at a concentration of 0.05 mM. The Brassica napus pot experiment involved inoculating HC02 using two methods: root irrigation treatment (IR02) and root dipping treatment (DR02). The growth of Brassica napus , its Sb content, the chemical properties of the rhizosphere soil, and the chemical forms of Sb present were analyzed. Results The oxidation rate of 0.05 mM Sb(III) by HC02 exceeds 90% within 48 h. HC02 possesses the ability to secrete 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and indole acetic acid (IAA). The addition of HC02 significantly promoted the growth of Brassica napus . Furthermore, both IR02 and DR02 treatments resulted in a significant reduction of total Sb content in roots, with decreases of 38.7% and 41.6%, respectively. Additionally, these treatments also led to a reduction in Sb(III) content in leaves, with reductions of 7.9% and 20.2%. Conclusions HC02 exhibits a strong oxidizing ability towards Sb(III). The incorporation of HC02 promotes the growth of Brassica napus while effectively preventing the absorption and accumulation of Sb. This research offers a theoretical foundation for the safe utilization of Sb-contaminated soil and the secure production of vegetables. Graphical • Lysinibacillus HC02 is a new highly efficient antimony-oxidizing bacterium. • Antimony toxicity of Brassica napus can be mitigate by Lysinibacillus HC02. • The mechanisms of HC02 regulating absorption and accumulation of Sb in Brassica napus was revealed.
Jihai Gu,Geoffrey Sunahara,Robert Duran,Jun Yao,Yongqiang Cui,CengCeng Tang,Hongquan Li,Victor G. Mihucz
Understanding the mechanism(s) of microbial resistance to antimony (Sb) is critical in the bioremediation of Sb polluted environments. Here a novel bacterium ( Acinetobacter sp. JH7) isolated from mine tailings decreased the Microtox toxicity of a Sb(III)-containing medium. DNA sequencing and physiological testing were employed for the identification and characterization of strain JH7. Following a batch experiment, Fourier transform infrared spectroscopy (FTIR) and antimony speciation analyses determined the adsorption and oxidation of antimony. Analyses of Sb(III) distribution revealed that extracellular polymeric substances and cell walls inhibited Sb(III) entry into JH7 cells. FTIR studies indicated that key functional groups including –OH, C–N, and C–O likely participated in Sb(III) biosorption. Isothermal and kinetic studies revealed that Sb(III) sorption to viable JH7 cells fitted the Langmuir model ( R 2 = 0.99) and could be described by pseudo-second order kinetics ( R 2 = 0.99). Furthermore, the increase of anti-oxidative enzymatic activity of JH7 enhanced the intracellular detoxification of Sb(III), which would indirectly contribute to the Sb(III) resistance ability of strain JH7. Our results indicate that biosorption and ROS oxidation of Sb(III) were likely responsible for the decreased toxicity of Sb. The greater understanding how Acinetobacter sp. JH7 lowers the environmental Sb(III) toxicity could provide a basis for future research and subsequent development of technologies for the remediation of Sb contaminated sites.
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