A 120-day in situ remediation of oil-contaminated soil was carried out by using highly efficient oil-degrading bacteria. The effects of bio-enhanced remediation and changes in soil physicochemical properties and enzyme activities were investigated. Combined with metagenomic sequencing and bioinformatics analysis, the strengthening mechanism was revealed. The results showed that compared with the blank control group (Ctrl), the degradation rate of total petroleum hydrocarbons in the bioremediation group (Exp-BT) was significantly increased, reaching 81.23%. During enhanced bioremediation by highly efficient oil-degrading bacteria, the pH of the soil was stable, the oxidation capacity of the system was improved, and the electrical conductivity was in the range suitable for agricultural activities. Lipase and dehydrogenase maintained high activity during repair. In addition, the analysis of the initial contaminated soil (B0), the highly efficient oil-degrading bacteria obtained from domestication (GZ), and the soil samples after bioremediation (BT) in the obtained samples showed that, at the phylum level, the total proportion of Proteobacteria and Actinobacteria increased by 17.1%. At the genus level, the abundance of Nocardioides, Achromobacter, Gordonia, and Rhodococcus increased significantly. The species and function contribution analysis of COG and KEGG proved that the above bacterial genera had important contributions to the degradation of petroleum hydrocarbons. A high abundance of petroleum hydrocarbon-related metabolic enzymes and five petroleum hydrocarbon-related degradation genes was found in the soil after remediation:alkM, tamA, rubB, ladA, and alkB. The analysis showed that the introduction of the exogenous petroleum hydrocarbon-degrading bacteria group enhanced the metabolic activity of microorganism-related enzymes and the expression of corresponding functional genes.
Keywords: functional genes; highly efficient petroleum-degrading bacteria; metabolic pathways; oil pollution; strengthening mechanism.