Distinct responses of aerobic and anaerobic soil microbial community structure and function to anthracene stress at environmental contamination levels

Anthracene (ANT) is widespread in terrestrial ecosystems, yet its impact on soil microbial community structure and function under varying oxygen conditions remains inadequately characterized. This study evaluated the responses of bacteria to ANT stress at environmental concentration (1.0 mg kg⁻¹) under aerobic and anaerobic soils. ANT contamination enriched potential polycyclic aromatic hydrocarbons (PAHs) degrading bacteria, such as Actinobacteriota, Prolixibacteraceae, and Nitrosomonadaceae, under both aerobic and anaerobic conditions. It also resulted in the proliferation of oligotrophic microorganisms under anaerobic condition. Additionally, ANT promoted the functions related to soil carbon, nitrogen and sulfur element cycling functions (Wilcoxon rank sum test, P < 0.05) and altered microbial carbon source utilization preferences in aerobic environment. However, under anaerobic conditions, ANT inhibited soil microbial element cycling, resulting in adverse effects. Furthermore, label-free proteomics quantitative analysis was conducted for aerobic treatment groups, revealing that the ANT contamination in soil altered the growth, metabolism and reproduction of bacteria. Up-regulated proteins were mainly concentrated in the Kyoto Encyclopedia of Genes and Genomes pathways related to amino acid and energy metabolism, which generated energy to satisfy physiological demanding under ANT stress. These results indicate that ANT at environmental contamination levels exhibit varying microbial effects under different oxygen conditions. Therefore, it is crucial to consider both its concentration and soil redox conditions when assessing the risk of PAH compounds.