Streptomyces pactum and sulfur mediated the antioxidant enzymes in plant and phytoextraction of potentially toxic elements from a smelter-contaminated soils.

The toxic potentially toxic metals elements (PTEs) discharged from industrial activities and agricultural practices persistently pose multiple hazards to environment and living organisms. Microbe-assisted phytoremediation provide an effective approach to remediate PTEs-contaminated soils. A phytoextraction process involved the application of Streptomyces pactum (Act12, 1.0, 2.0 and 3.0 g kg−1 dry soil, respectively) alone/jointly with sulfur was executed. The main texture of the tested soil was sandy loam and with a pH 8.27. The obtained results showed that the leaf pigments and plant biomass were improved after the application of the Act12, while the shoot fresh weight, chlorophyll a and chlorophyll b decreased by 57.8, 38.2 and 40.7%, respectively, after treatment with sulfur. Similarly, sulfur application facilitated the malondialdehyde (MDA) production by 18.4–33.6% compared to the control (no amendments). Both peroxidase (POD) and superoxide dismutase (SOD) activities were boosted, while the catalase (CAT) activity was suppressed with Act12 alone/jointly with sulfur treatment. The sulfur combined with elevated Act12 levels notably increased the cadmium (Cd) and zinc (Zn) concentrations both in shoots and roots, while the elemental extraction amount showed the removal efficiency following the order: Act12 alone ＞ control ＞ Act12 jointly with sulfur. Taken together, the results suggested that Streptomyces pactum and sulfur assisted the phytoremediation process, while further studies should be conducted in the field to test practical application.