Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, 1090GE Amsterdam, Noord-Holland, The Netherlands.
Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA.
Philos Trans R Soc Lond B Biol Sci. 2019 Nov 25;374(1786):20190090. doi: 10.1098/rstb.2019.0090. Epub 2019 Oct 7.
Photosynthesis in eukaryotes first arose through phagocytotic processes wherein an engulfed cyanobacterium was not digested, but instead became a permanent organelle. Other photosynthetic lineages then arose when eukaryotic cells engulfed other already photosynthetic eukaryotic cells. Some of the resulting lineages subsequently lost their ability for phagocytosis, while many others maintained the ability to do both processes. These mixotrophic taxa have more complicated ecological roles, in that they are both primary producers and consumers that can shift more towards producing the organic matter that forms the base of aquatic food chains, or towards respiring and releasing CO. We still have much to learn about which taxa are predatory mixotrophs as well as about the physiological consequences of this lifestyle, in part, because much of the diversity of unicellular eukaryotes in aquatic ecosystems remains uncultured. Here, we discuss existing methods for studying predatory mixotrophs, their individual biases, and how single-cell approaches can enhance knowledge of these important taxa. The question remains what the gold standard should be for assigning a mixotrophic status to ill-characterized or uncultured taxa-a status that dictates how organisms are incorporated into carbon cycle models and how their ecosystem roles may shift in future lakes and oceans. This article is part of a discussion meeting issue 'Single cell ecology'.
真核生物的光合作用最初是通过吞噬过程产生的，在这个过程中，被吞噬的蓝细菌没有被消化，而是成为了一个永久的细胞器。其他光合谱系则是当真核细胞吞噬其他已经具有光合作用的真核细胞时产生的。一些由此产生的谱系随后失去了吞噬的能力，而许多其他谱系则保持了同时进行这两种过程的能力。这些混合营养类群具有更复杂的生态角色，因为它们既是初级生产者又是消费者，可以更多地转向生产形成水生食物链基础的有机物质，或者转向呼吸和释放 CO。我们仍然有很多关于哪些类群是捕食性混合营养体以及这种生活方式的生理后果的知识需要了解，部分原因是水生生态系统中单细胞真核生物的多样性仍然没有得到培养。在这里，我们讨论了研究捕食性混合营养体的现有方法、它们各自的偏见，以及单细胞方法如何增强对这些重要类群的认识。问题仍然是，对于特征不明确或未培养的类群，应该将混合营养状态分配给它们的黄金标准是什么——这种状态决定了如何将生物体纳入碳循环模型，以及它们的生态角色在未来的湖泊和海洋中可能如何变化。本文是关于“单细胞生态学”的讨论会议的一部分。
