Lee Hanbyul, Hwang Kyuin, Cho Ahnna, Kim Soyeon, Kim Minkyung, Morgan-Kiss Rachael, Priscu John C, Kim Kyung Mo, Kim Ok-Sun
Division of Life Sciences, Korea Polar Research Institute, Yeonsu-Gu, Incheon, 21990, Republic of Korea.
Department of Microbiology, Miami University, Oxford, OH, 45056, USA.
Environ Microbiome. 2024 Aug 20;19(1):60. doi: 10.1186/s40793-024-00605-1.
Lake Bonney, which is divided into a west lobe (WLB) and an east lobe (ELB), is a perennially ice-covered lake located in the McMurdo Dry Valleys of Antarctica. Despite previous reports on the microbial community dynamics of ice-covered lakes in this region, there is a paucity of information on the relationship between microbial genomic diversity and associated nutrient cycling. Here, we applied gene- and genome-centric approaches to investigate the microbial ecology and reconstruct microbial metabolic potential along the depth gradient in Lake Bonney.
Lake Bonney is strongly chemically stratified with three distinct redox zones, yielding different microbial niches. Our genome enabled approach revealed that in the sunlit and relatively freshwater epilimnion, oxygenic photosynthetic production by the cyanobacterium Pseudanabaena and a diversity of protists and microalgae may provide new organic carbon to the environment. CO-oxidizing bacteria, such as Acidimicrobiales, Nanopelagicales, and Burkholderiaceae were also prominent in the epilimnion and their ability to oxidize carbon monoxide to carbon dioxide may serve as a supplementary energy conservation strategy. In the more saline metalimnion of ELB, an accumulation of inorganic nitrogen and phosphorus supports photosynthesis despite relatively low light levels. Conversely, in WLB the release of organic rich subglacial discharge from Taylor Glacier into WLB would be implicated in the possible high abundance of heterotrophs supported by increased potential for glycolysis, beta-oxidation, and glycoside hydrolase and may contribute to the growth of iron reducers in the dark and extremely saline hypolimnion of WLB. The suboxic and subzero temperature zones beneath the metalimnia in both lobes supported microorganisms capable of utilizing reduced nitrogens and sulfurs as electron donors. Heterotrophs, including nitrate reducing sulfur oxidizing bacteria, such as Acidimicrobiales (MAG72) and Salinisphaeraceae (MAG109), and denitrifying bacteria, such as Gracilimonas (MAG7), Acidimicrobiales (MAG72) and Salinisphaeraceae (MAG109), dominated the hypolimnion of WLB, whereas the environmental harshness of the hypolimnion of ELB was supported by the relatively low in metabolic potential, as well as the abundance of halophile Halomonas and endospore-forming Virgibacillus.
The vertical distribution of microbially driven C, N and S cycling genes/pathways in Lake Bonney reveals the importance of geochemical gradients to microbial diversity and biogeochemical cycles with the vertical water column.
邦尼湖分为西叶（WLB）和东叶（ELB），是南极洲麦克默多干谷中一个常年被冰覆盖的湖泊。尽管此前已有关于该地区冰盖湖泊微生物群落动态的报道，但关于微生物基因组多样性与相关养分循环之间关系的信息却很少。在此，我们应用以基因和基因组为中心的方法来研究邦尼湖沿深度梯度的微生物生态学，并重建微生物代谢潜力。
邦尼湖具有强烈的化学分层，有三个不同的氧化还原区，形成了不同的微生物生态位。我们基于基因组的方法表明，在阳光充足且相对淡水的湖面水层中，蓝细菌假鱼腥藻以及多种原生生物和微藻的有氧光合作用可能为环境提供新的有机碳。在湖面水层中，诸如酸微菌目、纳米浮游菌目和伯克霍尔德菌科等一氧化碳氧化细菌也很突出，它们将一氧化碳氧化为二氧化碳的能力可能作为一种补充性的能量守恒策略。在东叶盐度较高的温跃层中，尽管光照水平相对较低，但无机氮和磷的积累支持了光合作用。相反，在西叶，泰勒冰川向WLB释放富含有机物质的冰下径流，这可能与糖酵解、β-氧化和糖苷水解酶潜力增加所支持的异养生物的高丰度有关，并且可能有助于WLB黑暗且盐度极高的湖下层中铁还原菌的生长。两个叶层温跃层下方的缺氧和低温区支持能够利用还原态氮和硫作为电子供体的微生物。异养生物，包括硝酸盐还原硫氧化细菌，如酸微菌目（MAG72）和盐球菌科（MAG109），以及反硝化细菌，如纤细单胞菌属（MAG7）、酸微菌目（MAG72）和盐球菌科（MAG109），在WLB的湖下层中占主导地位，而ELB湖下层的环境恶劣程度则表现为代谢潜力相对较低，以及嗜盐菌嗜盐单胞菌属和产芽孢的维尔吉芽孢杆菌的丰度较高。
邦尼湖中微生物驱动的碳、氮和硫循环基因/途径的垂直分布揭示了地球化学梯度对水柱垂直方向上微生物多样性和生物地球化学循环的重要性。
