Metagenomic study of carbon metabolism in black soil microbial communities under lead-lanthanum stress

Pollution of soil environments with heavy metals (HMs) and rare earth elements (REEs) cannot be ignored. We aimed to determine the effects of lead combined with lanthanum (Pb-La) on microbial community structure, carbon metabolism, and differences in carbon source utilization in black soils using EcoPlatesTM and a macrogenomic approach. We found that Pb and La contents and the microbial community structure together influence and shape the response of soil carbon metabolism to Pb-La. Compared with controls, microorganisms under pollution stress preferentially use phenolic and carboxylic acids as growth carbon sources. Under Pb-La stress, the relative abun-dance of Proteobacteria significantly increased, thereby selectively displacing heavy metal-sensitive phyla, such as Chloroflexi, Acidobacteria, and Thaumarchaeota. Altered functional potential of the microbial carbon cycle man-ifested as differences in carbon metabolism, methane metabolism, and carbon fixation pathways. Furthermore, an appropriate concentration of La can reduce the environmental toxicity of Pb, whereas a high concentration of La has synergistic toxicity with Pb. These findings have important implications for understanding the impact of HM-REE contamination in microbial communities and the functions associated with carbon metabolism in black soils.