Degradation of C30 - Reduced TCA cycle rates at high hydrostatic pressure hinder hydrocarbon degradation and obligate oil degraders in natural, deep-sea microbial communities

A significant part of the heavier petroleum fraction resulting from offshore oil-spills sinks to the deep-sea. Its fate and biodegradation by microbial communities is unclear. In particular, the physiological and metabolic features of hydrostatic pressure (HP) adapted oil-degraders have been neglected. In this study, hydrocarbon-free sediment from 1km below surface water (bsl) was incubated at 0.1, 10 and 20MPa (equivalent to surface waters, 1 and 2km bsl) using triacontane (C30) as sole carbon source for a 3-month enrichment period. HP strongly impacted biodegration, as it selected for microbial communities with small cells, high O2 respiration and nutrients requirements, but low biomass and C30-degradation yields. The alkane-degrading metaproteome linked to β-oxidation was detected but its expression was reduced under HP contrary to several housekeeping genes. This was reflected in the enriched communities, as atmospheric pressure was dominated by hydrocarbonoclastic bacteria while non-specialized or previously unrecognized oil-degrading genera were enriched under HP.

海上溢油产生的重质石油馏分中有相当一部分会沉降至深海区域，但其归宿以及微生物群落介导的生物降解过程目前仍不明确。尤为关键的是，适静压（hydrostatic pressure, HP）的石油降解微生物的生理与代谢特征长期被忽视。本研究以距表层海水1千米（below surface water, bsl）的无烃沉积物为研究对象，以三十烷（triacontane, C30）作为唯一碳源，在0.1、10及20MPa（分别对应表层海水、1千米及2千米bsl的环境压力）条件下开展为期3个月的富集培养。静压显著影响了石油降解过程：高压环境筛选出的微生物群落具有细胞体积小、氧气呼吸及营养需求高，但生物量与三十烷降解产率较低的特征。研究检测到与β-氧化途径相关的烷烃降解宏蛋白质组，但与持家基因不同的是，其在静压条件下的表达量显著下调。这一结果在富集群落的组成中得到体现：常压环境下的富集群落以食烃细菌（hydrocarbonoclastic bacteria）为主，而静压条件下则富集得到非特化或此前未被认知的石油降解菌属。