Cd resistant characterization of mutant strain irradiated by carbon-ion beam.

Heavy metal pollution is harmful to the environment and to human health. Resistant strains can grow in adverse conditions and store heavy metals to reduce their damage. The Cd2+ resistant mutant strain C2, which was irradiated by the 12C6+ beams, can grow in Cd medium ranging from 20 to 100 mg L-1 when compared with the original strain. Attempting to discern the cause of the resistance, the phenotype and antioxidant defense system were analyzed. SEM images showed that when exposed to Cd2+, gaps on the cell surface were filled with a complex granular compound. FT-IR demonstrated that the alcoholic hydroxyl group, amino, and amide groups combined with ions. Moreover, responses of antioxidant defense system were different in the Cd2+ groups. The expression of SOD peaked at 24 h in high concentrations of Cd2+; the content of GSH increased gradually and was significantly affected by cultivation time. The MDA and CAT had the strongest response to 20 mg L-1 Cd2+, and the related metabolic pathway of CAT might play a key role in the resistance to high concentrations of Cd2+. The result indicated that the applicability of C2 could provide potential biotechnology for treatment of wastewaters and soils with Cd pollutions.