Effects of soil chemical properties and fractions of Pb, Cd, and Zn on bacterial and fungal communities.

Heavy metal contamination in soils poses a serious threat to microorganisms, which play important roles in soil biogeochemical process. However, the key fractions of heavy metals affecting soil microorganisms are still unclear. In this study, DNA sequencing, redundancy and variance partition analysis were performed to investigate the combined effects of heavy metal fractions and soil chemical properties on microbial communities in Pb, Cd, and Zn co-contaminated soils. The results showed that long-term exposure of microorganisms to these metals changed the richness, diversity, and structure of their communities. The bacterial and fungal Chao richness indexes decreased, but only the bacterial Shannon index improved with increasing metal concentrations. Moreover, soil available potassium and acid-extractable Pb made the greatest contributions to variations in the bacterial community structure, while soil pH, water-extractable Pb and Zn were the dominant factors influencing the fungal community structure. In addition, Marmoricola, Nocardioides, and Gibberella were sensitive to these metals. Overall, the effects of different heavy metal fractions on microorganisms varied significantly, and these metal fractions together with soil chemical properties determined the soil microbial communities.