Institut de Biologie de l'École Normale Supérieure, École Normale Supérieure, Paris Sciences et Lettres Research University, CNRS UMR 8197, INSERM U1024, F-75005, Paris, France.
Station Biologique de Roscoff, Sorbonne Universités, UPMC Université Paris 06, CNRS, UMR7144, 29680, Roscoff, France.
ISME J. 2018 Apr;12(4):1094-1108. doi: 10.1038/s41396-017-0029-1. Epub 2018 Jan 18.
Diatoms are a diverse and ecologically important group of phytoplankton. Although most species are considered free living, several are known to interact with other organisms within the plankton. Detailed imaging and molecular characterization of any such partnership is, however, limited, and an appraisal of the large-scale distribution and ecology of such consortia was never attempted. Here, observation of Tara Oceans samples from the Benguela Current led to the detection of an epibiotic association between a pennate diatom and a tintinnid ciliate. We identified the diatom as Fragilariopsis doliolus that possesses a unique feature to form barrel-shaped chains, associated with seven different genera of tintinnids including five previously undescribed associations. The organisms were commonly found together in the Atlantic and Pacific Ocean basins, and live observations of the interaction have been recorded for the first time. By combining confocal and scanning electron microscopy of individual consortia with the sequencing of high-resolution molecular markers, we analyzed their distribution in the global ocean, revealing morpho-genetically distinct tintinnid haplotypes and biogeographically structured diatom haplotypes. The diatom was among the most abundant in the global ocean. We show that the consortia were particularly prevalent in nutrient-replete conditions, rich in potential predators. These observations support the hypothesis of a mutualistic symbiosis, wherein diatoms acquire increased motility and tintinnids benefit from silicification through increased protection, and highlight that such associations may be more prevalent than currently appreciated.
硅藻是一类多样且具有重要生态意义的浮游植物。尽管大多数物种被认为是自由生活的，但已知有几种与浮游生物中的其他生物相互作用。然而，对任何这种伙伴关系的详细成像和分子特征描述都受到限制，并且从未尝试评估这种共生体的大规模分布和生态学。在这里，对本格拉海流中 Tara Oceans 样本的观察导致了发现了一种有肋硅藻和纤毛滴虫之间的附生关联。我们将硅藻鉴定为 Fragilariopsis doliolus，它具有形成桶形链的独特特征，与七个不同属的纤毛滴虫有关，其中包括五个以前未描述的关联。这些生物体通常在大西洋和太平洋盆地中一起发现，并首次记录了它们相互作用的活体观察。通过对单个共生体进行共聚焦和扫描电子显微镜观察以及高分辨率分子标记物的测序，我们分析了它们在全球海洋中的分布情况，揭示了形态上不同的纤毛滴虫单倍型和具有生物地理结构的硅藻单倍型。硅藻是全球海洋中最丰富的生物之一。我们表明，在富含营养物质的条件下，共生体特别普遍，其中富含潜在的捕食者。这些观察结果支持了互利共生的假说，即硅藻获得了更高的运动能力，而纤毛滴虫通过增加保护而受益于硅化，并强调了这种关联可能比目前所认识的更为普遍。
