"Pomacytosis"-Semi-extracellular phagocytosis of cyanobacteria by the smallest marine algae.
"Pomacytosis"-Semi-extracellular phagocytosis of cyanobacteria by the smallest marine algae.
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最小的海洋藻类对蓝细菌的细胞细胞吞噬作用。
DOI：
10.1371/journal.pbio.2003502
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发表时间：
2018-01
期刊：
影响因子：
9.8
通讯作者：
Zubkov MV
中科院分区：
文献类型：
--
作者：
Kamennaya NA;Kennaway G;Fuchs BM;Zubkov MV
最小的藻类直径小于3 μm，是世界海洋中最丰富的真核生物。它们以类似大小的浮游细菌为食，这在全球都很重要，但在物理上却是个谜。微小的藻类细胞被大量的叶绿体、细胞核和线粒体紧密包裹，似乎没有足够的无细胞器空间来内化猎物。在这里，我们首次直接观察到1.3 μm的藻类（直径仅为其猎物的1.6倍）如何将单个原绿球藻细胞保存在其开放的半球细胞孔中。我们将这种半细胞外吞噬解释为具有固氮（N2）内共生体的掠食性藻类Braarudosphaera haptophyte的细胞大小限制。由于观察到的半细胞外吞噬不同于所有其他类型的原体吞噬，我们建议将其命名为“pomacytosis”（来自希腊语πώμα，意为“堵塞”）。微生物的全球意义是它们天文数字数量的结果。对于地球上最小的浮游藻类（直径小于3 μm）和海洋中数量最多的真核生物来说，这当然是正确的。与一般认为藻类只利用阳光和溶解的矿物质营养物质生长相反，这些微小的植物消耗大量的细菌。它们像小型捕食者一样捕食与自己体型相近的细菌，这很难想象。一个微小的藻类细胞被细胞器（如细胞核、线粒体、叶绿体）挤得很挤，细胞内根本没有空间以通常的方式吞噬一个大细菌。为了了解直径1.3 μm的褐藻是如何进食的，我们利用高分辨率电子显微镜对其进行了研究。我们发现藻类处理猎物的方式不同于所有其他类型的细胞进食。我们表明，这种藻类将直径0.8 μm的猎物保存在开放的胞壁（细胞口）中，并且从浮游细菌中，藻类显然选择了一种球状的原绿球藻（一种丰富的蓝藻，负责大多数全球光合作用），它像塞子一样紧密地融入开放的胞壁。我们观察到，藻类没有完全消化猎物，而是留下了甜甜圈形状的猎物尸体。我们得出的结论是，这种微小的掠食性藻类的这种不寻常的进食，我们称之为“pomacytosis”，主要是由其细胞内的空间限制引起的。
The smallest algae, less than 3 μm in diameter, are the most abundant eukaryotes of the World Ocean. Their feeding on planktonic bacteria of similar size is globally important but physically enigmatic. Tiny algal cells tightly packed with the voluminous chloroplasts, nucleus, and mitochondria appear to have insufficient organelle-free space for prey internalization. Here, we present the first direct observations of how the 1.3-μm algae, which are only 1.6 times bigger in diameter than their prey, hold individual Prochlorococcus cells in their open hemispheric cytostomes. We explain this semi-extracellular phagocytosis by the cell size limitation of the predatory alga, identified as the Braarudosphaera haptophyte with a nitrogen (N2)–fixing endosymbiont. Because the observed semi-extracellular phagocytosis differs from all other types of protistan phagocytosis, we propose to name it “pomacytosis” (from the Greek πώμα for “plug”). The global significance of microorganisms is a consequence of their astronomical numbers. This is certainly true for the smallest planktonic algae on earth, which are less than 3 μm in diameter and the most numerous eukaryotic organisms of the oceans. Contrary to the general belief that algae use only sunlight and dissolved mineral nutrients to grow, these microscopic plants consume large numbers of bacteria. Their acting as mini-predators on bacteria of nearly their own size is hard to imagine. A tiny algal cell is cramped with organelles—such as nucleus, mitochondria, chloroplasts—and there is simply no space inside this cell to engulf a large bacterium in the usual manner. To find out how the 1.3-μm–diameter haptophyte algae feed, we studied them using high-resolution electron microscopy. We found that prey handling by the alga differs from all other types of cell feeding. We showed that this alga holds the 0.8-μm–diameter prey in the open cytostome (cell mouth) and that, from among planktonic bacteria, the alga apparently selects a ball-shaped Prochlorococcus (an abundant cyanobacteria responsible for most of global photosynthesis) that tightly fits into the open cytostome like a plug. Instead of full prey digestion, we observed that the alga leaves behind the doughnut-shaped carcass of the prey. We conclude that such unusual feeding, which we call “pomacytosis”, of this tiny predatory alga is caused primarily by the space limitation inside its cell.
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影响因子：
14.9
作者：
Klindworth A;Pruesse E;Schweer T;Peplies J;Quast C;Horn M;Glöckner FO
通讯作者：
Glöckner FO
影响因子：
2.9
作者：
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通讯作者：
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影响因子：
1.5
作者：
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通讯作者：
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影响因子：
4.5
作者：
NYGAARD, K;TOBIESEN, A
通讯作者：
TOBIESEN, A
影响因子：
4.4
作者：
Schloss, Patrick D.;Westcott, Sarah L.;Weber, Carolyn F.
通讯作者：
Weber, Carolyn F.