Anaerobic petroleum biodegradation by microbial communities enriched from mangrove sediments

Mangrove sediments are increasingly exposed to petroleum contamination; however, the anaerobic degradation of petroleum hydrocarbons by sediment-derived microbial communities remains poorly understood. In this study, anaerobic microbial communities were enriched in sediments collected from three mangrove wetlands using petroleum as the sole carbon source and nitrate/sulfate as dual electron acceptors. The enriched communities exhibited a strong capacity for petroleum hydrocarbon degradation, with degradation ranging from 65.20% to 93.20% for total petroleum hydrocarbons and from 64.68% to 99.92% for alkanes (C13-C30). The dominant bacterial genera included Pseudomonas, Bacillus, Shewanella, and Desulfocurvibacter. Microbial taxa such as Shewanella carried key genes involved in hydrocarbon transformation, including alkane degradation genes assA/masD and aromatic hydrocarbon degradation genes bssA/nmsA. Through the fumarate addition pathway, these microorganisms mediated hydrocarbon activation and generated metabolites that were subsequently utilized by sulfate- and nitrate-reducing bacteria, thereby promoting electron transfer and supporting nitrogen and sulfur cycling. Methane production was associated with the methanogenic archaeon Methanofollis, indicating the establishment of a syntrophic petroleum degradation network under anaerobic conditions. Overall, this study provides new insights into anaerobic petroleum biodegradation by microbial communities enriched from mangrove sediments.