Thiocyanate-degrading microflora alleviates thiocyanate stress on tomato seedlings by improving plant and rhizosphere microenvironment

Thiocyanate in irrigation water can adversely affect plant growth and development. A previously constructed microflora with effective thiocyanate-degrading ability was used to investigate the potential of bacterial degradation for thiocyanate bioremediation. The root and aboveground part dry weight of plants inoculated with the degrading microflora increased by 66.67% and 88.45%, respectively, compared to those plants without the microflora. The supplementation of thiocyanate-degrading microflora (TDM) significantly alleviated the interference of thiocyanate in mineral nutrition metabolism. Moreover, the supplementation of TDM significantly reduced the activities of antioxidant enzymes, lipid peroxidation, and DNA damage and it protected plants from excessive thiocyanate, while the crucial antioxidant enzyme (peroxidase) decreased by 22.59%. Compared with the control without TDM supplementation, the soil sucrase content increased by 29.58%. The abundances of Methylophilus, Acinetobacter, unclassified Saccharimonadales, and Rhodanobacter changed from 19.92%, 6.63%, 0.79%, and 3.90%-13.19%, 0.27%, 3.06%, and 5.14%, respectively, with TDM supplementation. Caprolactam, 5,6-dimethyldecane, and pentadecanoic acid seem to have an effect on the structure of the microbial community in the rhizosphere soil. The above results indicated TDM supplementation can significantly reduce the toxic effects of thiocyanate on the tomato-soil microenvironment.