The effects of polycyclic aromatic hydrocarbons on ecological assembly processes and co-occurrence patterns differ between soil bacterial and fungal communities

Polycyclic aromatic hydrocarbons (PAHs) are hazardous organic pollutants prevalent in soil ecosystems. Bacteria and fungi play important roles in the degradation of PAHs in the soils. However, little is known about the differences between the bacterial and fungal community assemblies in PAH-contaminated soils. In this study, soil bacterial and fungal community distributions were investigated in maize farmlands and roadside barelands around nine coking plants in Shanxi, China. Most of the soil samples were severely polluted with PAHs. A clear microbial biogeographic pattern was observed. Bacterial communities are primarily affected by environmental factors, whereas fungal communities are primarily affected by spatial factors. Null modeling showed that homogeneous selection (deterministic processes) and dispersal limitation (stochastic processes) dominated the bacterial and fungal community assemblages, respectively. PAH concentrations were closely linked to community assembly processes, and influenced microbial co-occurrence by mediating specific network modules. Overall, the effects of PAHs on bacterial community assembly and co-occurrence relationships were greater than those on fungal communities. Some microbial taxa associated with PAH degradation can be considered potential biomarkers that reflect the degree of PAH pollution. These results expand the understanding of the mechanisms underlying the assembly and maintenance of soil microbial communities in response to PAH contamination.