Due to the increasing pollution by petroleum hydrocarbons (PHs), it is an important task to develop eco-friendly and highly efficient methods for remediating petroleum-contaminated soils. In this study, bioremediation technology was applied to remediate PHs contaminated soils, and the bacterial community structure and physicochemical characteristics of the soil treated using different bioremediation regimens were analyzed. Compared with the control condition (S0), the PHs removal efficiency of biostimulation (S2) and bioaugmentation (S3) was increased significantly. Combined biostimulation with bioaugmentation (S4) had the highest PHs removal efficiency, up to 60.14 ± 4.12%. Among all the selected remediation strategies (S1–S4, S1: soil moisture content: 25–30%), the bacterial alpha-diversity was higher than in S0. The genera Acinetobacter, Escherichia-Shigella, Bacteroides, Microbacterium, and Parabacteroides were found to greatly contribute to PHs’ degradation. In the group S4, the PH-degraders and soil enzyme activity were higher than in the other remediation regimens, and these indices gradually decreased in the mid-to-later periods of all remediation tests. Additionally, the abundance of alkB and nah genes was increased by improving the environmental condition of the microorganism communities. Redundancy analysis (RDA) revealed that the total nitrogen (TN) and total phosphorus (TP) had a positive correlation with total PHs degradation. This study offers insights into the microbial community response to environmental factors during bioremediation, which shows a promoting effect in enhancing the efficiency of PHs remediation.

BACKGROUND: Surfactant-enhanced remediation (SER) has been widely applied to remove petroleum hydrocarbon (PH) pollutants, but there are few studies on the mechanism through which surfactants affect the hydrocarbon metabolite ability of microorganism. RESULTS: In this work, combination bacteria and surfactant were selected to remove PH, and the degradation bottleneck concentration of single-bacteria was 10 g L -1 according to the PH degradation rate. However, the degradation efficient of mixed-bacteria was further increased after adding surfactants. Among them, the PH degradation rate of Kocuria rosea + Bacillus odyssey and Microbacterium. sp + B. odyssey at the bottleneck concentration had been respectively reached to 81.58 ± 6.29% with tween-80 and 88.35 ± 7.58% with rhamnolipid. Compared with no surfactant, the relative abundance of global overmaps, amino acid metabolism, and carbohydrate metabolism was increased in adding tween-80 condition. However, when rhamnolipid was added, the relative abundance of ABC transporters, two-component system, and bacteria chemotaxis was clearly increased, indicating an improvement of transportation, absorption, and degradation of PH. Additionally, the gene abundance of alkB and nah was also significantly increased with above condition. Meanwhile, the gene abundance of alkB and nah was also significantly enhanced by above condition.CONCLUSION: This study offers new insights into the functional changes of mixed-bacteria during PH degradation in different surfactant-enhanced systems.