Sinking enhances the degradation of organic particles by marine bacteria
Sinking enhances the degradation of organic particles by marine bacteria
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DOI：
10.1038/s41561-021-00817-x
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发表时间：
2021-09-23
影响因子：
18.3
通讯作者：
Stocker, Roman
中科院分区：
文献类型：
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作者：
Alcolombri, Uria;Peaudecerf, Francois J.;Stocker, Roman
海洋中有机颗粒的下沉及其被海洋微生物降解是生物泵的主要驱动力之一。然而，决定泵的大小的机制仍然知之甚少，限制了我们预测未来海洋情景中碳通量的能力。目前的海洋模型假设生物泵是由下沉速度和降解速度之间的竞争，这两个过程相互独立。与此相反，我们表明，下沉本身是细菌降解颗粒的速率的主要决定因素。异养细菌的降解率，从一个实验室的研究模型表面定殖颗粒在大气压下的流速范围内，以模仿不同的下沉速度。我们发现，即使是温和的下沉速度8米天（-1）提高降解率超过10倍的非下沉颗粒的降解率相比。我们发现，这种下沉增强的降解的分子机制是流动诱导的低聚物分解产物的颗粒，否则竞争酶活性的去除。这种机制适用于几种底物和细菌菌株，表明其在天然海洋条件下可能广泛存在。将我们的研究结果整合到一个颗粒碳通量的数学模型中，我们提出，下沉和降解的耦合可能有助于与其他过程相结合，以确定海洋中垂直碳通量的大小。更快的下沉速率可以增强海洋中有机颗粒的细菌降解，这是由于流动引起的废物去除，根据实验室试验和船用碳泵模型，
The sinking of organic particles in the ocean and their degradation by marine microorganisms is one of the main drivers of the biological pump. Yet, the mechanisms determining the magnitude of the pump remain poorly understood, limiting our ability to predict this carbon flux in future ocean scenarios. Current ocean models assume that the biological pump is governed by the competition between sinking speed and degradation rate, with the two processes independent from one another. Contrary to this paradigm, we show that sinking itself is a primary determinant of the rate at which bacteria degrade particles. Heterotrophic bacterial degradation rates were obtained from a laboratory study on model surface-colonized particles at atmospheric pressure under a range of flow speeds to mimic different sinking velocities. We find that even modest sinking speeds of 8 m day(-1) enhance degradation rates more than 10-fold compared with degradation rates of non-sinking particles. We discovered that the molecular mechanism underlying this sinking-enhanced degradation is the flow-induced removal from the particles of the oligomeric breakdown products, which otherwise compete for enzymatic activity. This mechanism applies across several substrates and bacterial strains, suggesting its potentially broad occurrence under natural marine conditions. Integrating our findings into a mathematical model of particulate carbon flux, we propose that the coupling of sinking and degradation may contribute, in conjunction with other processes, to determining the magnitude of the vertical carbon flux in the ocean.Faster sinking rates can enhance bacterial degradation of organic particles in the ocean due to flow-induced removal of waste products, according to laboratory experiments and modelling of the marine carbon pump.