Effect of multiple heavy metals pollution to bacterial diversity and community structure in farmland soils

Abstract

Heavy metal pollution poses a serious hazard to the soil bacterial community. In this study, the 16 s rRNA high-throughput sequencing technology was used to analyze bacterial diversity and structure of dry field soil at different levels of heavy metal pollution. Further, the relationships between soil parameters and bacterial community were analyzed. Based on the study findings, we classified the levels of heavy metal pollution in soil samples from the study area could be divided into four grades: high risk (HR), considerable risk (CR), moderate risk (MR) and low risk (LR). In this study, heavy metal concentrations and pH showed significant effect on bacterial community structure. The distribution of bacterial community richness and diversity was MR > LR > CR > HR. Bacterial communities such as Acidobacteria, Chloroflexi and Gemmatimonadetes were highly resistant to the lower pH (pH < 6.5) and the high levels of heavy metal pollution compared with other bacterial community, which were abundant in HR samples. However, Proteobacteria, Actinobacteria, Bacteroidetes and Latescibacteria were more abundant in alkaline soils (pH > 7.5). Further, available Cd, Pb and Zn concentrations were lower in alkaline soils than acidic soils, which reduced the impact of heavy metals on bacterial community diversity and structure.