Densely Populated Water Droplets in Heavy-Oil Seeps
Densely Populated Water Droplets in Heavy-Oil Seeps
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DOI：
10.1128/aem.00164-20
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发表时间：
2020-06-01
影响因子：
4.4
通讯作者：
Meckenstock, R. U.
中科院分区：
文献类型：
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作者：
Pannekens, M.;Voskuhl, L.;Meckenstock, R. U.
据信油藏中的大部分微生物降解发生在油水过渡带（OWTZ）。然而，最近的一项研究表明，在特立尼达和多巴哥的沥青湖重油中分散的微升大小的水滴中存在着微生物生命。石油中的这种生命表明，石油的微生物降解也发生在独立于 OWTZ 的油段的含油岩石的水囊中。然而，尚不清楚分散在油中的水滴中的微生物是否是油藏的普遍特性，而不是一种奇异的例外。因此，我们从三个重油渗漏处采集了样本：Pitch Lake（特立尼达和多巴哥）、La Brea Tar Pits（美国加利福尼亚州）和 McKittrick 油田（美国加利福尼亚州）的一个油渗漏处。所有三个测试的油渗漏都含有分散的水滴。 1 至 10 μl 之间的较大液滴显示出高达 10(9) 个细胞 ml(-1) 的高细胞密度。 ATP 含量和 LIVE/DEAD 染色测试表明，这些种群由活跃且有活力的微生物细胞组成，平均有 60% 的膜完整细胞，并且 ATP 浓度与其他地下生态系统相当。基于 16S rRNA 基因扩增子测序的微生物群落分析揭示了已知厌氧石油降解微生物的存在。令人惊讶的是，群落分析显示所有三个油渗点之间存在相似性，揭示了共同的 OTU，尽管采样点相距数千公里。我们的结果表明，小水包裹体是稠油中密集的微生境，可能是退化油藏的普遍特征。重要性我们的结果证实，油中的小水滴是含有活跃微生物群落的密集微生境。由于这些微生境发生在三个相距数千公里的测试油渗漏处，因此这些聚集的水滴可能是生物降解油藏的普遍特征，并且可能参与整个石油降解过程。因此，微生物降解也可能发生在储层岩石的含油油段的水囊中，而不仅仅是在油水过渡区。
Most of the microbial degradation in oil reservoirs is believed to take place at the oil-water transition zone (OWTZ). However, a recent study indicates that there is microbial life enclosed in microliter-sized water droplets dispersed in heavy oil of Pitch Lake in Trinidad and Tobago. This life in oil suggests that microbial degradation of oil also takes place in water pockets in the oil-bearing rock of an oil leg independent of the OWTZ. However, it is unknown whether microbial life in water droplets dispersed in oil is a generic property of oil reservoirs rather than an exotic exception. Hence, we took samples from three heavy-oil seeps, Pitch Lake (Trinidad and Tobago), the La Brea Tar Pits (California, USA), and an oil seep on the McKittrick oil field (California, USA). All three tested oil seeps contained dispersed water droplets. Larger droplets between 1 and 10 mu l revealed high cell densities of up to 10(9) cells ml(-1). Testing for ATP content and LIVE/DEAD staining showed that these populations consist of active and viable microbial cells with an average of 60% membrane-intact cells and ATP concentrations comparable to those of other subsurface ecosystems. Microbial community analyses based on 16S rRNA gene amplicon sequencing revealed the presence of known anaerobic oil-degrading microorganisms. Surprisingly, the community analyses showed similarities between all three oil seeps, revealing common OTUs, although the sampling sites were thousands of kilometers apart. Our results indicate that small water inclusions are densely populated microhabitats in heavy oil and possibly a generic trait of degraded-oil reservoirs.IMPORTANCE Our results confirmed that small water droplets in oil are densely populated microhabitats containing active microbial communities. Since these microhabitats occurred in three tested oil seeps which are located thousands of kilometers away from each other, such populated water droplets might be a generic trait of biodegraded oil reservoirs and might be involved in the overall oil degradation process. Microbial degradation might thus also take place in water pockets in the oil-bearing oil legs of the reservoir rock rather than only at the oil-water transition zone.