Effects of sulfate amendment and different temperatures on microbial community structure and hydrocarbon degradation in petroleum-contaminated soils

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Environmental temperature fluctuations have substantial effects on sulfate-mediated anaerobic remediation of petroleum-contaminated soils, yet systematic investigations into the underlying mechanisms and temperature-dependent degradation signatures remain limited. In this study, hydrocarbon degradation in oxygen-limited microcosms and microbial community succession were characterized over successive remediation stages. Degradation efficiencies increased with increasing temperature across the tested thermal gradients (5 °C, 20 °C, and 40 °C). Compared with control groups, the total hydrocarbon removal efficiency was significantly greater in sulfate-amended groups. All temperature treatments resulted in a similar degradation pattern: rapid hydrocarbon removal during the initial phase, followed by gradual deceleration during later incubation stages. Functional prediction revealed enrichment of gene families involved in fatty acid metabolism, ABC-type transport systems, and stress-responsive sigma factors. High-throughput sequencing revealed that Pseudomonadota , Actinomycetota , Bacillota , and Planctomycetota were the dominant microbial taxa whose relative abundances fluctuated in response to temperature, sulfate amendment, and remediation duration. Collectively, these findings suggest that sulfate addition and incubation temperature jointly modulate hydrocarbon-degradation dynamics. Nevertheless, temperature, rather than sulfate amendment, was the primary factor structuring microbial-community composition.