The medium- and long-chain n-alkane released from natural and anthropogenic oil spill can enter deep ocean even the bottom of Mariana Trench, causing ecological risk for its toxicity and bio-resistant. Microbial degradation is the dominant and ultimate natural removal process for n-alkane in deep ocean. High hydrostatic pressure (HHP) is a distinctive characteristic in deep ocean and has been broadly reported regulate microbial activity. The knowledge gap on the impact of HHP on n-alkane degradation in deep ocean constrains the precise evaluation for ecological effects of n-alkanes. To address this, we applied deep ocean experimental simulator to culture Alcanivorax xenomutans A28, a novel piezotolerant bacterium strain isolated from 7663.5 m sediment, with n-C₁₆ as sole carbon source under different HPs (0.1, 40, 80 MPa) and at 4℃. We found that HHPs inhibited n-C₁₆ consumption and stimulated complete mineralization, causing higher CO₂ production risk when decomposing n-alkane in deeper ocean. The transcriptomic and metabolomic analysis indicated that the HHP accelerated TCA cycle and high intracellular H₂O₂ level to stimulate complete mineralization of n-C₁₆. Furthermore, HHPs inhibited the n-alkane oxygenation with monooxygenase alkB significantly down regulated thus causing low n-C₁₆ consumption and trigger potential isozyme gene almA providing functional compensation to a certain extend. Overall, this study clearly demonstrated that how HHP regulates the alkane biodegradation and therefore stirs the fate of alkane as well as related carbon cycling, leading to a revisit to deep ocean alkane clean-up and carbon budget calculation.
 

hydrostatic pressure,alkane biodegradation,complete mineralization