Dissolved organic carbon (DOC) is an important source of carbon and energy for microbes, but whether it can be used by phytoplankton has not been systematically studied, and the underlying molecular metabolism remains poorly understood. Here, we investigated the ability of phytoplankton to utilize glycerol as a representative of DOC. The widespread presence and expression of glycerol transporter genes were found in transcriptomes and genomes, suggesting the glycerol utilization potential in the diverse marine phytoplankton. We surveyed 29 representative phytoplankton species (31 strains) from six phyla for their ability to use glycerol. Three types of responses were found: positive utilization (Type I), no response (Type II), and negative response (Type III). In all, 11 Type I species were further investigated in axenic cultures with different glycerol concentrations, and five species showed intrinsic glycerol utilizing ability without the aid of bacteria. The ability of species to use glycerol to support non‐photosynthetic (DCMU treated) growth was consistent with their possession and expression of glycerol transporter genes. However, some species from the Type II and Type III also possess and express the genes, raising a question whether glycerol transporter in algae might have diversified its function to glycerol export or even non‐glycerol transport. Our results show that glycerol could serve as organic carbon source, harmless xenobiotics, or growth inhibitors for phytoplankton depending on species, indicating that glycerol, including natural sources or human discharges, may shape the marine phytoplankton community structure, especially under low photosynthetic efficiency conditions.

中文翻译：

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浮游植物对甘油的利用1。

溶解性有机碳（DOC）是微生物的重要碳和能量来源，但是尚未对其浮游植物可利用的有机碳进行系统的研究，对潜在的分子代谢仍知之甚少。在这里，我们研究了浮游植物利用甘油作为DOC代表的能力。在转录组和基因组中发现了甘油转运蛋白基因的广泛存在和表达，表明甘油在多种海洋浮游植物中的利用潜力。我们调查了来自六个门的29个代表性浮游植物（31个品系）使用甘油的能力。发现了三种类型的响应：积极利用（I型），无响应（II型）和负面响应（III型）。在所有，在具有不同甘油浓度的树胶培养物中进一步研究了11种I型菌种，其中5种在没有细菌帮助的情况下显示出内在的甘油利用能力。物种利用甘油支持非光合作用（DCMU处理）生长的能力与其拥有和表达甘油转运蛋白基因一致。但是，来自II型和III型的某些物种也拥有并表达该基因，这引发了一个疑问：藻类中的甘油转运蛋白是否可能使其功能多样化，从而可以输出甘油，甚至非甘油转运。我们的研究结果表明，甘油可以用作有机碳源，无害的异种生物或浮游植物的生长抑制剂，具体取决于物种，这表明甘油，包括自然来源或人类排泄物，