Microbial communities in petroleum-contaminated seasonally frozen soil and their response to temperature changes.

Petroleum has contaminated microbial habitats in some parts of permafrost. The microbial community has probably undergone great changes due to the differential sensitivity of bacteria to petroleum contamination, making the seasonally frozen ground ecosystem even more fragile. In this study, we analyzed the microbial community structure and function at different soil depths and petroleum contaminant levels, and studied their relationship with environmental factors through correlation analysis, the random forest algorithm and co-occurrence network analysis. We found that microbial community composition and function mainly varied in response to concentrations of petroleum and sulfates in the environment. The microbial community was divided into six modules as functional groups. Among them, sulfate-reducing bacteria and sulfite-oxidizing bacteria play important roles in module0 and module4, respectively, which were possibly responsible for the degradation of petroleum in permafrost zone. The microbial ability to degrade petroleum decreased and glycan metabolism decreased and then increased through the temperature rise-fall process as a result of microbial stress tolerance mechanisms to pollution and temperature changes. The impact on microbial community structure and function, as well as the responses to petroleum pollution and temperature changes, are revealed in this study.