Douglas Channel and the adjacent Hecate Strait (British Columbia, Canada) are part of a proposed route to ship diluted bitumen (dilbit). This study presents how two types of dilbit naturally degrade in this environment by using an in situ microcosm design based on dilbit-coated beads. We show that dilbit-associated n-alkanes were microbially biodegraded with estimated half-lives of 57–69 days. n-Alkanes appeared to be primarily degraded using the aerobic alkB, ladA and CYP153 pathways. The loss of dilbit polycyclic aromatic hydrocarbons (PAHs) was slower than of n-alkanes, with half-lives of 89–439 days. A biodegradation of PAHs could not be conclusively determined, although a significant enrichment of the phnAc gene (a marker for aerobic PAH biodegradation) was observed. PAH degradation appeared to be slower in Hecate Strait than in Douglas Channel. Microcosm-associated microbial communities were shaped by the presence of dilbit, deployment location and incubation time but not by dilbit type. Metagenome-assembled genomes of putative dilbit-degraders were obtained and could be divided into populations of early, late and continuous degraders. The majority of the identified MAGs could be assigned to the orders Flavobacteriales, Methylococcales, Pseudomonadales and Rhodobacterales. A high proportion of the MAGs represent currently unknown lineages or lineages with currently no cultured representative.

中文翻译：

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在不列颠哥伦比亚省（加拿大）海岸部署的原位微观世界，用于研究海洋条件下的稀释石风化和相关微生物群落

道格拉斯海峡和邻近的赫卡特海峡（加拿大不列颠哥伦比亚省）是运输稀释沥青（dilbit）的拟议航线的一部分。本研究通过使用基于稀释石涂层珠子的原位微观设计，展示了两种类型的稀释石如何在这种环境中自然降解。我们发现，与稀释比特相关的正构烷烃可被微生物生物降解，估计半衰期为 57-69 天。正烷烃似乎主要通过需氧alk B、lad A 和 CYP153 途径降解。重比特多环芳烃 (PAH) 的损失比正烷烃慢，半衰期为 89-439 天。尽管观察到phnAc基因（需氧 PAH 生物降解的标记）显着富集，但仍无法最终确定 PAH 的生物降解。赫卡特海峡的多环芳烃降解速度似乎比道格拉斯海峡慢。微观世界相关的微生物群落是由稀释石的存在、分布位置和培养时间决定的，而不是由稀释石的类型决定的。获得了假定的稀释剂降解者的宏基因组组装基因组，并且可以将其分为早期、晚期和持续降解者群体。大多数已鉴定的 MAG 可归属于黄杆菌目、甲基球菌目、假单胞菌目和红杆菌目。很大一部分 MAG 代表目前未知的谱系或目前没有培养代表的谱系。