Organic matter degradation in marine environments is essential for the recycling of nutrients, especially under conditions of anoxia where organic matter tends to accumulate. However, little is known about the diversity of the microbial communities responsible for the mineralization of organic matter in the absence of oxygen, as well as the factors controlling their activities. Here, we determined the active heterotrophic prokaryotic community in the sulphidic water column of the Black Sea, an ideal model system, where a tight coupling between carbon, nitrogen and sulphur cycles is expected. Active microorganisms degrading both dissolved organic matter (DOM) and protein extracts were determined using quantitative DNA stable isotope probing incubation experiments. These results were compared with the metabolic potential of metagenome-assembled genomes obtained from the water column. Organic matter incubations showed that groups like Cloacimonetes and Marinimicrobia are generalists degrading DOM. Based on metagenomic profiles the degradation proceeds in a potential interaction with members of the Deltaproteobacteria and Chloroflexi Dehalococcoidia. On the other hand, microbes with small genomes like the bacterial phyla Parcubacteria, Omnitrophica and of the archaeal phylum Woesearchaeota, were the most active, especially in protein-amended incubations, revealing the potential advantage of streamlined microorganisms in highly reduced conditions.

中文翻译：

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多种未培养的微生物群落是黑海硫化物区有机物降解的原因

海洋环境中的有机物降解对于营养物的循环利用至关重要，特别是在有机物容易积累的缺氧条件下。然而，人们对缺氧情况下负责有机物矿化的微生物群落的多样性以及控制其活动的因素知之甚少。在这里，我们确定了黑海硫化物水体中活跃的异养原核生物群落，这是一个理想的模型系统，预计碳、氮和硫循环之间存在紧密耦合。使用定量 DNA 稳定同位素探测孵育实验确定降解溶解有机物 (DOM) 和蛋白质提取物的活性微生物。将这些结果与从水柱中获得的宏基因组组装基因组的代谢潜力进行比较。有机物孵化表明，像Cloacimonetes和Marinimicrobia这样的群体是降解 DOM 的多面手。根据宏基因组图谱，降解在与Deltaproteobacteria和Chloroflexi Dehalococcoidia成员的潜在相互作用中进行。另一方面，具有小基因组的微生物，如细菌门 Parcubacteria 、 Omnitropica和古菌门Woesearchaeota，是最活跃的，特别是在蛋白质改良的孵化中，揭示了在高度还原条件下精简微生物的潜在优势。