Oxidative and antioxidative responses to antimony stress by endophytic fungus Aspergillus tubingensis isolated from antimony accumulator Hedysarum pallidum Desf.

Antimony (Sb) is a toxic metalloid whose pollution has become a serious problem. However, studies on fungal endophytes resistant to antimony are virtually nonexistent. An endophytic fungal strain was isolated for the first time from the roots of Hedysarum pallidum Desf. which is a Sb accumulator Fabacea growing on mine cuttings. Experiments with high Sb increased concentrations (0, 5, 10, 20 and 30 mM Sb) were performed in order to assess the strain potential in contaminated environments bioremediation and to understand its Sb tolerance strategy. The isolated strain was identified as Aspergillus tubingensis MH189391 by morphological characteristics and phylogenetic analysis. It exhibited a minimum inhibitory concentration (MIC) of 500 mM Sb, i.e. 60,880 mg L −1 , and maintained high amounts of biomass up to 30 mM Sb, i.e. 3652.8 mg L −1 of Sb. A stimulation of A. tubingensis growth and its antioxidant responses was observed at the level of 5 mM Sb, i.e. 609 mg L −1 . Hydrogen peroxide (H 2 O 2 ) and malondialdehyde (MDA) contents increased significantly ( p < 0.05) with Sb treatments. Oxidative stress induced significant increases (p < 0.05) in antioxidant biomarkers such as proline, catalase (CAT), and superoxide dismutase (SOD), but it resulted in a significant decrease of peroxidase (POD) and ascorbate peroxidase (APX) activities. Proline, CAT, SOD, H 2 O 2 and MDA were significantly ( p < 0.05) and positively correlated, which highlights their coactions in oxidative stress fighting. Results indicate that Aspergillus tubingensis has developed an important adaptation to excessive Sb concentrations and that it could be used in antimony-contaminated environments bioremediation.