Novel insights into quorum-sensing microbe combined with dimethylsulfoniopropionate enhancing bioremediation of oil-contaminated sediment under typical deep-sea conditions: The performances and molecular mechanisms.

The deep-sea environment poses significant metabolic challenges to microorganisms, rendering the bioremediation of oil pollution even more formidable. Quorum sensing (QS) signals are known to assist microbiota in maintaining their function and stability under toxic contaminants. Dimethylsulfoniopropionate (DMSP) is an ideal cryoprotectant and stress protectant, enhancing microbial resilience in extreme environments. Given these, the comprehensive investigations on the application of QS bacteria and DMSP in restoring oil-polluted sediment were conducted at deep-sea microcosm over two months. First, a strain of QS signals-producing bacteria coexisting with DMSP was isolated. Then, a high-efficiency oil elimination was observed in polluted sediment treated by the bacteria jointly with DMSP, with a degradation rate about 40 % higher than the control. Via detection of meta- and metabolically-active microbes and biochemical experiment, the molecular-ecological mechanisms of such combination were associated with the following aspects: 1) the expedited biofilm formation, as evidenced by the hyper-expressive pathways involving proteins and lipid biosynthesis, bacterial secretory system and cell motility, as well as the increasing production of extracellular polymeric substances; 2) the improved microbial adaptation, as shown by more complex community network and upregulated expressing activity of pathways related to DNA repair and transcription; 3) the facilitated electron transport process, as exhibited by the increased expression in cell-respiratory pathways of such as cytochrome c. Overall, our results offer valuable theoretical guidance and empirical support for the application of QS system in remediation of oil-polluted sediment at real deep sea.