Effects of Long-Term Heavy Metal Pollution on Microbial Community Structure in Soil

Heavy metal (HM) contamination of soil is a worldwide problem with adverse consequences for the environment and human health. Microorganisms, as the most active fraction in soil, play a pivotal role in assessing changes in soil quality and maintaining ecological equilibrium. Accordingly, screening efficient microorganisms for remediating contaminated soils has emerged as a key research focus. This study employed high-throughput sequencing and conducted in situ field surveys to investigate the impacts of long-term HM pollution with varying severity on soil physicochemical properties, as well as the community structure and diversity of bacteria and fungi. The results showed that the major soil physiochemical properties and the bacterial and fungal β diversity significantly changed with the increase in HM pollution levels. The relative abundances of Chloroflexi, Myxococcota and Nitrospirota among bacteria, along with Chytridiomycota and Talaromyces among fungi, increased significantly with rising HM pollution levels. In low-, medium- and highly contaminated soils, the dominant bacterial species were OTU10618 (Micrococcales), OTU6447 (Chthoniobacterales), and OTU7447 (Burkholderiales), while the dominant fungal species were OTU3669 (Glomerellales), OTU397 (Olpidiales), and OTU2568 (Mortierellales). Bacterial communities were mainly affected by soil-available phosphorus, available cadmium (Cd) and available Pb, while fungal communities were predominantly influenced by soil-available phosphorus, soil organic carbon and total Pb content. These findings demonstrate that soil microorganisms in chronically HM-contaminated soils exhibit adaptive shifts, and this study thereby provides critical implications for assessing the remediation potential of diverse microbial taxa in HM-polluted soils.