Distinct bacterial community structure, assembly and functions between aged and multiple petroleum-contaminated sites

Petroleum contamination threatens soil ecosystems, but microbial responses to multi-contaminated area (MCA) and aged-contaminated area (ACA) remain unclear. This study compared bacterial communities in MCA and ACA at China's Lanzhou Petrochemical Site using 16S rRNA sequencing, network analysis and PICRUSt2. MCA had 12-fold higher total petroleum hydrocarbons than ACA, and MAHs and PAHs in MCA were 201-fold and 10-fold higher. PAHs drove bacterial communities in MCA, while those in ACA were shaped by ecological toxicity assessed by whole-cell bioreporter. The network structure of MCA was complex (more modules, positive edges and keystone taxa), whereas that of ACA was relatively simplified. Bacterial community assembly in MCA involved both stochastic (83.09 %) and deterministic (16.91 %) processes, whereas there was only stochastic process in ACA. Bacteria in MCA exhibited stronger carbohydrate metabolic capabilities related to fresh hydrocarbon utilization, whereas those in ACA were more inclined toward amino acid metabolism and membrane transport functions. Our study provides a thorough exploration of soil bacterial response and assembly mechanisms under various petroleum pollution scenarios, offering guidance for developing customized bioremediation strategies in oil-contaminated environments. • First comparison of bacterial communities between aged and multiple contaminated sites. • Contaminant levels affect bacterial communities and metabolic genes in MCA. • Petroleum toxicity and bioavailability affected bacterial communities and functions in ACA. • Higher complexity of bacterial network in MCA than in ACA. • Stronger hydrocarbon metabolism of bacterial communities in MCA.