Novel agents consisting of Pseudomonas zhaodongensis and dimethylsulfoniopropionate (DMSP) enhancing bioremediation of oil-contaminated sediments at deep-sea condition

Deep-sea environments are featured by low temperature and high hydrostatic pressure, which inhibits petroleum hydrocarbon metabolism by microorganisms. Herein, we developed novel bioremediating agents composed of different combinations of Pseudomonas zhaodongensis and dimethylsulfoniopropionate (DMSP) to promote oil degradation at deep-sea microcosm environment. First, through transcriptome sequencing, we revealed DMSP might provide hydrostatic pressure protection via secretion of potential piezolytes within the cell, which let bacteria healthy growth and thereby promoted oil biodegradation. Then, via oil measurement and high-throughput sequencing, we assessed effectiveness on using the studied agents and indigenous microorganism (i.e., natural remediation) to restore oil-contaminated muddy and sandy sediments at the microcosm, and demonstrated: 1) Oil degradation efficiency among different treatments using agents was 23.47 % – 41.02 % higher than that in natural remediation; 2) Each remediation plan defined specialized bacterial community. Marinobacter, Idiomarina, Sulfitobacter, Ferrimonas, Halodesulfovibrio, Paramaledivibacter and Pseudomonas were keystone oil-degrading taxa; 3) Overall, microbial community in sediment samples treated by bioremediation agents obtained better diversification of trophic interactions, structure stability and interference resistance; 4) Compared to natural remediation, pathways involving in oil component degradation and biogeochemical cycling exhibited varying degrees of up-regulation in agent-treated groups. Altogether, these results emphasize the crucial role of P. zhaodongensis and DMSP in enhancing bioremediation of oil-polluted sediments at typical deep-sea condition, and provide a novel idea for in-situ restoration of oil pollution at deep sea in future.