SRP410100 PRJNA905712 Metagenomic study on carbon metabolism of black soil microbial community under Pb-La coexistence stress At present, the combined pollution of heavy metals (HMs) and rare earths (REEs) in the soil environment cannot be ignored. In this study, we investigated the effects of Pb-La on microbial community structure, carbon metabolism function and differences in carbon source utilization in black soils through Biolog-ECO method and macrogenomic experiments. Results showed that Pb and La content and microbial community structure together influence and shape the response of soil carbon metabolism to Pb-La. Compared with the control, microorganisms under pollution stress prefer to use phenolic acid and carboxylic acid as growth carbon sources. Under Pb-La stress, the relative abundance of Proteobacteria increased significantly, selectively displacing heavy metal-sensitive phyla such as Chloroflexi, Acidobacteria and Thaumarchaeota. In addition, the functional potential of the microbial carbon cycle changes, as evidenced by differences in carbon metabolism, methane metabolism and carbon fixation pathways. Furthermore, an appropriate concentration of La could reduce environmental toxicity of Pb, while the high concentration of La had synergistic toxicity with Pb. These data have important implications for exploring the impact of microbial communities and functions involved in carbon metabolism in black soils under combined HMs-REEs contamination.