Li Wei, Podar Mircea, Morgan-Kiss Rachael M
Department of Microbiology, Miami University, Oxford, Ohio, USA.
Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.
Appl Environ Microbiol. 2016 May 31;82(12):3659-3670. doi: 10.1128/AEM.00478-16. Print 2016 Jun 15.
The McMurdo Dry Valleys (MCM) of southern Victoria Land, Antarctica, harbor numerous ice-covered bodies of water that provide year-round liquid water oases for isolated food webs dominated by the microbial loop. Single-cell microbial eukaryotes (protists) occupy major trophic positions within this truncated food web, ranging from primary producers (e.g., chlorophytes, haptophytes, and cryptophytes) to tertiary predators (e.g., ciliates, dinoflagellates, and choanoflagellates). To advance the understanding of MCM protist ecology and the roles of MCM protists in nutrient and energy cycling, we investigated potential metabolic strategies and microbial interactions of key MCM protists isolated from a well-described lake (Lake Bonney). Fluorescence-activated cell sorting (FACS) of enrichment cultures, combined with single amplified genome/amplicon sequencing and fluorescence microscopy, revealed that MCM protists possess diverse potential metabolic capabilities and interactions. Two metabolically distinct bacterial clades (Flavobacteria and Methylobacteriaceae) were independently associated with two key MCM lake microalgae (Isochrysis and Chlamydomonas, respectively). We also report on the discovery of two heterotrophic nanoflagellates belonging to the Stramenopila supergroup, one of which lives as a parasite of Chlamydomonas, a dominate primary producer in the shallow, nutrient-poor layers of the lake.
Single-cell eukaryotes called protists play critical roles in the cycling of organic matter in aquatic environments. In the ice-covered lakes of Antarctica, protists play key roles in the aquatic food web, providing the majority of organic carbon to the rest of the food web (photosynthetic protists) and acting as the major consumers at the top of the food web (predatory protists). In this study, we utilized a combination of techniques (microscopy, cell sorting, and genomic analysis) to describe the trophic abilities of Antarctic lake protists and their potential interactions with other microbes. Our work reveals that Antarctic lake protists rely on metabolic versatility for their energy and nutrient requirements in this unique and isolated environment.
南极洲维多利亚地南部的麦克默多干谷（MCM）有众多被冰覆盖的水体，为以微生物环为主导的孤立食物网提供了全年的液态水绿洲。单细胞微生物真核生物（原生生物）在这个截断的食物网中占据主要营养位置，从初级生产者（如绿藻、定鞭藻和隐藻）到三级捕食者（如纤毛虫、甲藻和领鞭毛虫）。为了增进对MCM原生生物生态学以及MCM原生生物在营养和能量循环中作用的理解，我们研究了从一个描述详尽的湖泊（博尼湖）分离出的关键MCM原生生物的潜在代谢策略和微生物相互作用。对富集培养物进行荧光激活细胞分选（FACS），结合单扩增基因组/扩增子测序和荧光显微镜观察，发现MCM原生生物具有多样的潜在代谢能力和相互作用。两个代谢不同的细菌类群（黄杆菌和甲基杆菌科）分别与两种关键的MCM湖泊微藻（等鞭金藻和衣藻）独立相关。我们还报告了发现属于不等鞭毛总门的两种异养型纳米鞭毛虫，其中一种以衣藻为寄生虫，衣藻是该湖浅水、贫营养层中的主要初级生产者。
被称为原生生物的单细胞真核生物在水生环境中的有机物质循环中发挥着关键作用。在南极洲被冰覆盖的湖泊中，原生生物在水生食物网中起关键作用，为食物网的其他部分提供大部分有机碳（光合原生生物），并作为食物网顶端的主要消费者（捕食性原生生物）。在这项研究中，我们利用多种技术（显微镜观察、细胞分选和基因组分析）来描述南极湖泊原生生物的营养能力及其与其他微生物的潜在相互作用。我们的工作表明，在这个独特而孤立的环境中，南极湖泊原生生物依靠代谢多样性来满足其能量和营养需求。
