Louca Stilianos, Rubin Ilan N, Madilao Lufiani L, Bohlmann Jörg, Doebeli Michael, Wegener Parfrey Laura
Department of Biology, University of Oregon, Eugene, OR, USA.
Institute of Ecology and Evolution, University of Oregon, Eugene, OR, USA.
Environ Microbiol Rep. 2020 Oct;12(5):514-524. doi: 10.1111/1758-2229.12866. Epub 2020 Aug 3.
Surveys of microbial systems indicate that in many situations taxonomy and function may constitute largely independent ('decoupled') axes of variation. However, this decoupling is rarely explicitly tested experimentally, partly because it is hard to directly induce taxonomic variation without affecting functional composition. Here we experimentally evaluate this paradigm using microcosms resembling lake sediments and subjected to two different levels of salinity (0 and 19) and otherwise similar environmental conditions. We used DNA sequencing for taxonomic and functional profiling of bacteria and archaea and physicochemical measurements to monitor metabolic function, over 13 months. We found that the taxonomic composition of the saline systems gradually but strongly diverged from the fresh systems. In contrast, the metabolic composition (in terms of proportions of various genes) remained nearly identical across treatments and over time. Oxygen consumption rates and methane concentrations were substantially lower in the saline treatment, however, their similarity either increased (for oxygen) or did not change significantly (for methane) between the first and last sampling time, indicating that the lower metabolic activity in the saline treatments was directly and immediately caused by salinity rather than the gradual taxonomic divergence. Our experiment demonstrates that strong taxonomic shifts need not directly affect metabolic rates.
对微生物系统的调查表明，在许多情况下，分类学和功能可能构成很大程度上独立的（“解耦的”）变异轴。然而，这种解耦很少通过实验进行明确测试，部分原因是很难在不影响功能组成的情况下直接诱导分类学变异。在这里，我们使用类似于湖泊沉积物的微观世界进行实验评估这一范式，并使其处于两种不同的盐度水平（0和19）以及其他相似的环境条件下。我们使用DNA测序对细菌和古菌进行分类学和功能分析，并通过物理化学测量来监测代谢功能，持续了13个月。我们发现，盐度系统的分类组成逐渐但强烈地与淡水系统分化。相比之下，代谢组成（就各种基因的比例而言）在不同处理之间以及随时间保持几乎相同。然而，盐度处理中的氧气消耗率和甲烷浓度显著较低，它们在第一次和最后一次采样时间之间的相似性要么增加（对于氧气），要么没有显著变化（对于甲烷），这表明盐度处理中较低的代谢活性是由盐度直接且即时引起的，而不是逐渐的分类学分化。我们的实验表明，强烈的分类学变化不一定直接影响代谢率。
