Limnological Observatory of the Pyrenees (LOOP)-Biogeodynamics & Biodiversity Interactions Group, CEAB-CSIC, Centre d'Estudis Avançats de Blanes-CSIC, Girona, Spain.
ISME J. 2012 Sep;6(9):1786-97. doi: 10.1038/ismej.2012.33. Epub 2012 Apr 12.
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 (o)C 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 changed their relative abundances with water depth being higher in surface and lower in depth for SAGMGC-1 than for MG 1.1a, reflecting a vertical phylogenetic segregation. Overall, the relative abundance and recurrent appearance of SAGMGC-1 suggests a significant environmental role of this clade in alpine lakes. These results expand the set of ecological and thermal conditions where Thaumarchaeota are distributed, unveiling vertical positioning in the water column as a key factor to understand the ecology of different thaumarchaeotal clades in lacustrine environments.
淡水生境被认为是古菌遗传多样性的最大储存库之一，氨氧化古菌（AOA）的特定种群与土壤和海洋不同。然而，关于湖泊 AOA 的生态学和生物学仍知之甚少。本研究通过 CARD-FISH、定量 PCR（qPCR）分析和克隆文库鉴定，对西班牙比利牛斯山脉中心的高山深冰川湖雷东（Redon）湖中的古菌丰度的垂直变化与环境参数进行了相关性分析。大气沉降物是该地区活性氮的主要来源。在垂直梯度上发现了 Thaumarchaeotal 16S rRNA 基因、古菌 amoA 基因和亚硝酸盐浓度之间的强烈相关性，表明这些微生物具有氨氧化潜力。未检测到细菌 amoA 基因。在垂直梯度上揭示了三个具有潜在氨氧化活性的深度，（i）在冬季-春季（即冰盖下的糊状层上方的 0°C 冰渣层）的湖顶，（ii）在温跃层和（iii）夏季-秋季的底部水域。总体而言，高达 90%的 16S rRNA 基因序列与 Thaumarchaeota 匹配，主要来自 Marine Group (MG) 1.1a（类似于 Nitrosoarchaeum 的古菌）和姐妹分支 SAGMGC-1（类似于 Nitrosotalea 的古菌）。克隆文库分析表明，随着水深的增加，两个分支的相对丰度发生了变化，与 MG 1.1a 相比，SAGMGC-1 在表层的相对丰度较高，而在深层的相对丰度较低，反映了垂直的系统发育分离。总体而言，SAGMGC-1 的相对丰度和反复出现表明该分支在高山湖泊中具有重要的环境作用。这些结果扩展了 Thaumarchaeota 分布的生态和温度条件的范围，揭示了水柱中的垂直定位是理解湖泊中不同 Thaumarchaeotal 分支生态的关键因素。
