Keystone taxa of phoD-harboring bacteria mediate alkaline phosphatase activity during biochar remediation of Cd-contaminated soil
Qiang Wang, Chengjiao Duan, Zengchao Geng, Chenyang Xu
Abstract
Phosphorus (P)-modified biochar can efficiently remediate cadmium (Cd)-contaminated soil. However, the mechanisms of responses of alkaline phosphatase (ALP) and phoD -harboring microorganisms , which are notably sensitive to Cd and P, are not clear during the remediation process. In this study, apple ( Malus domestica ) tree branches were co-pyrolyzed with tripotassium phosphate (K 3 PO 4 ) to prepare P-modified biochar, which was used to remediate Cd-soil contaminated soil collected near a mine site. The effect of P-modified biochar on the composition of the phoD -harboring microbial community and its mechanism of interacting with ALP were analyzed. The results showed that the application of P-modified biochar to Cd-contaminated soil promoted the co-precipitation of Cd and phosphate and reduced the content of bioavailable Cd by 69.77 %. P-modified biochar improved the complexity and stability of the soil phoD -harboring microbial community . Furthermore, this study clarified that ALP activity was not completely regulated by the abundance of phoD , but Priestia and Massilia that contain phoD genes dominated the activity of ALP in rhizosphere and bulk soils, respectively. It is notable that bioavailable Cd significantly stimulated Priestia , Massilia , and ALP activity. These findings provide a theoretical basis for the application of P-modified biochar to the remediation of soil contaminated with Cd with respect to P functional microorganisms.