Medium-chain alkanes have strong ecological impacts on marine ecosystems due to their persistence, toxicity, and ability to travel long distances. Microbial degradation is the dominant and ultimate removal process for n-alkanes in the deep ocean, where high hydrostatic pressure (HHP) regulates microbial activity. To gain insight into the impact of hydrostatic pressure (HP) on n-alkane degradation, we applied the deep-ocean experimental simulation to culture Alcanivorax xenomutans A28, a novel piezotolerant bacterium strain from trench sediment, with n-C 16 as the sole carbon source under different HPs (0.1, 40, and 80 MPa). Activity analysis demonstrated that HHP stimulated the n-C 16 complete mineralization ratio. Transcriptomic and metabolomic analyses showed that HHP induced the intracellular oxidative stress and accelerated the tricarboxylic acid (TCA) cycle. These results indicate a shift of n-alkanes biodegradation pattern regulated by HP, elucidating the fate and ecological risk of n-alkanes in the deep ocean.
Soil microbial communities are usually regarded as one of the key players in the global element cycling. Moreover, an important consequence of oil contamination altering the structure of microbial communities is likely to result in an increased carbon emission. However, understanding of the complex interactions between environmental factors and biological communities is clearly lagging behind. Here it showed that the flux of carbon emissions increased in oil-contaminated soils, up to 13.64 g C·(kg soil) −1 ·h −1 . This phenomenon was mainly driven by the enrichment of rare degrading microorganisms (e.g., Methylosinus , Marinobacter , Pseudomona s, Alcanivorax , Yeosuana , Halomonas and Microbulbifer ) in the aerobic layer, rather than the anaerobic layer, which is more conducive to methane formation. In addition, petroleum hydrocarbons and environmental factors are equally important in shaping the structure of microbial communities (the ecological stability) and functional traits (e.g., fatty acid metabolism, lipid metabolism and amino acid metabolism) due to the different ecological sensitivities of microorganisms. Thus, it can be believed that the variability of rare hydrocarbon degrading microorganisms is of greater concern than changes in dominant microorganisms in oil-contaminated soil. Undoubtedly, this study could reveal the unique characterization of bacterial communities that mediate carbon emission and provide evidence for understanding the conversion from carbon stores to carbon gas release in oil-contaminated soils.
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