Freshwater habitats have been identified as one of the largest reservoirs of archaeal genetic diversity, with specific lineages of ammonia-oxidizing archaea (AOA) populations different from soils and seas. The ecology and biology of lacustrine AOA is, however, poorly known. In the present study, vertical changes in archaeal abundance by CARD-FISH, quantitative PCR (qPCR) analyses and identity by clone libraries were correlated with environmental parameters in the deep glacial high-altitude Lake Redon. The lake is located in the central Spanish Pyrenees where atmospheric depositions are the main source of reactive nitrogen. Strong correlations were found between abundance of thaumarchaeotal 16S rRNA gene, archaeal amoA gene and nitrite concentrations, indicating an ammonium oxidation potential by these microorganisms. The bacterial amoA gene was not detected. Three depths with potential ammonia-oxidation activity were unveiled along the vertical gradient, (i) on the top of the lake in winter–spring (that is, the 0 oC slush layers above the ice-covered sheet), (ii) at the thermocline and (iii) the bottom waters in summer—autumn. Overall, up to 90% of the 16S rRNA gene sequences matched Thaumarchaeota, mostly from both the Marine Group (MG) 1.1a (Nitrosoarchaeum-like) and the sister clade SAGMGC−1 (Nitrosotalea-like). Clone-libraries analysis showed the two clades changedtheir relative abundances with water depth being higher in surface and lower in depth forSAGMGC−1 than for MG 1.1a, reflecting a vertical phylogenetic segregation. Overall,the relative abundance and recurrent appearance of SAGMGC−1 suggests a significantenvironmental role of this clade in alpine lakes. These results expand the set ofecological and thermal conditions where Thaumarchaeota are distributed, unveiling verticalpositioning in the water column as a key factor to understand the ecology of differentthaumarchaeotal clades in lacustrine environments.
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机译：淡水生境已被确定为古细菌遗传多样性的最大储存库之一，具有特定的氨氧化古细菌（AOA）种群世系，不同于土壤和海洋。然而，人们对湖泊AOA的生态学和生物学知之甚少。在本研究中，CARD-FISH的古细菌丰度的垂直变化，定量PCR（qPCR）分析和克隆文库的鉴定与深冰川高海拔雷东湖的环境参数相关。该湖位于西班牙比利牛斯山脉中部，那里的大气沉积物是活性氮的主要来源。发现拟南芥16S rRNA基因的丰度，古细菌amoA基因与亚硝酸盐的浓度之间存在很强的相关性，表明这些微生物的铵氧化潜力。未检测到细菌amoA基因。沿垂直梯度揭示了具有潜在氨氧化活性的三个深度，（i）冬春季的湖顶（即，冰雪覆盖层上方的0 o C融雪层）表），（ii）恒温器和（iii）夏季的底水-秋季。总体而言，高达90％的16S rRNA基因序列与Thaumarchaeota匹配，主要来自海洋群（MG）1.1a（类似Nitrosoarchaeum）和姐妹进化枝SAGMGC-1（类似Nitrosotalea）。克隆库分析显示两个进化枝已改变它们相对丰度，水深在表层较高而在深度较低SAMGGC-1比MG 1.1a高，反映了垂直的系统发育隔离。总体，SAGMGC-1的相对丰度和复发现象表明进化枝在高山湖泊中的环境作用。这些结果扩展了Thaumarchaeota分布的生态和热条件，揭示了垂直定位在水柱中是了解不同生态的关键因素湖泊环境中的丘脑进化枝。
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