Contrasting response of rice rhizosphere microbiomes to in situ cadmium-contaminated soil remediation

Understanding the responses of different rhizosphere microbial lineages to soil amendments during in situ remediation of Cd-contaminated soil is of great importance in the assessment of the restoration and crop health. This study demonstrates the distinct responses of rice rhizosphere microbial communities to soil amendment applications, highlighting the interactive associations between microbiomes, which is vital for enhancing our ability to develop effective strategies for sustainable soil management. The researchers' findings appeared December 4, 2023 in Soil Ecology Letters.

A series of studies on the diversities and interactions of rice rhizosphere microbial communities have been conducted by Jiachun Shi's team at the Zhejiang University, and many interesting findings have been obtained. For example, they found that soil pH was the key factor affecting the proportion of available Cd in total Cd during Cd-contaminated soil remediation. The bacterial community was more sensitive to soil amendment-induced changes, and treatments with pig-manure and commercial Mg-Ca-Si conditioner significantly increased the relative abundances of protistan phototrophs. Notably, co-occurrence network analysis revealed that soil amendments increased microbial network complexity and triggered the role of protists, especially for the predatory protists Cercozoa, on microbial trophic interactions. Also, the bacteria community was a more important biotic driver of the protistan community.

In this study, their results show that application of soil amendments immobilized available Cd in soil and altered the microbial communities in the rhizosphere of rice under in situ Cd-contaminated soil remediation. Among three microbial lineages investigated in this study, bacteria communities turned out as the most sensitive microbial group to soil amendments-induced changes in soil properties. Lime and biochar increased the relative abundances of protistan consumers, and pig manure and commercial conditioner significantly promoted the relative abundances of phototrophs. Interestingly, all four amendments enhanced the potential crucial role of protistan taxa Cercozoa in regulating the interactions with microbes. The edaphic properties such as pH, SOM, NO₃^--N, C/N ratio and bacterial and fungal communities were found to be important abiotic and biotic factors driving protistan community assembly.