Unité d'Ecologie; Systématique et Evolution, CNRS, Université Paris-Sud, Université Paris-Saclay, AgroParisTech, bâtiment 360, 91400 Orsay, France.
Department of Biospeleology and Karst Edaphobiology, Emil Racovita Institute of Speleology, Bucharest, Romania.
Environ Microbiol Rep. 2019 Jun;11(3):464-473. doi: 10.1111/1758-2229.12756. Epub 2019 Apr 26.
Movile Cave is a small system of partially inundated galleries in limestone settings close to the Black Sea in Southeast Romania. Isolated from the surface for 6 million years, its sulfidic, methane and ammonia-rich waters harbour unique chemosynthetic prokaryotic communities that include sulphur and ammonium-metabolizing chemolithotrophs, methanogens, methanotrophs and methylotrophs. The cave also harbours cave-dwelling invertebrates and fungi, but the diversity of other microbial eukaryotes remained completely unknown. Here, we apply an 18S rRNA gene-based metabarcoding approach to study the composition of protist communities in floating microbial mats and plankton from a well-preserved oxygen-depleted cave chamber. Our results reveal a wide protist diversity with, as dominant groups, ciliates (Alveolata), Stramenopiles, especially bicosoecids, and jakobids (Excavata). Ciliate sequences dominated both, microbial mats and plankton, followed by either Stramenopiles or excavates. Stramenopiles were more prominent in microbial mats, whereas jakobids dominated the plankton fraction of the oxygen-depleted water column. Mats cultured in the laboratory were enriched in Cercozoa. Consistent with local low oxygen levels, Movile Cave protists are most likely anaerobic or microaerophilic. Several newly detected OTU clades were very divergent from cultured species or environmental sequences in databases and represent phylogenetic novelty, notably within jakobids. Movile Cave protists likely cover a variety of ecological roles in this ecosystem including predation, parasitism, saprotrophy and possibly diverse prokaryote-protist syntrophies.
莫威利洞穴是罗马尼亚东南部黑海附近石灰岩环境中一个部分被淹没的小型画廊系统。它与地表隔绝了 600 万年，其富含硫化物、甲烷和氨的水域拥有独特的化能合成原核生物群落，包括硫和铵代谢化能自养生物、产甲烷菌、甲烷氧化菌和甲基营养菌。洞穴还栖息着洞穴无脊椎动物和真菌，但其他微生物真核生物的多样性仍然完全未知。在这里，我们应用基于 18S rRNA 基因的宏条形码方法来研究保存在缺氧洞穴室内的浮游微生物垫和浮游生物中原生生物群落的组成。我们的结果揭示了广泛的原生生物多样性，优势群体为纤毛虫（纤毛门）、不等鞭毛类（Stramenopiles），特别是双壳目（Bicosoecida）和 jakobids（挖掘真核生物）。纤毛虫序列在微生物垫和浮游生物中均占主导地位，其次是不等鞭毛类或挖掘真核生物。不等鞭毛类在微生物垫中更为突出，而 jakobids 则在缺氧水柱的浮游部分中占主导地位。在实验室中培养的垫子富含 Cercozoa。与当地低氧水平一致，莫威利洞穴原生生物很可能是厌氧或微需氧的。一些新检测到的 OTU 分支与数据库中的培养物种或环境序列非常不同，代表了系统发育的新颖性，特别是在 jakobids 中。莫威利洞穴原生生物可能在这个生态系统中扮演着多种生态角色，包括捕食、寄生、腐生，以及可能与各种原核生物-原生生物共生。
