Department of Environmental Chemistry, Swiss Federal Institute of Aquatic Science and Technology, Eawag, Überlandstrasse 133, 8600, Dübendorf, Switzerland.
Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, 8092, Zürich, Switzerland.
ISME J. 2019 Jun;13(6):1589-1601. doi: 10.1038/s41396-019-0371-6. Epub 2019 Feb 20.
A remaining challenge within microbial ecology is to understand the determinants of richness and diversity observed in environmental microbial communities. In a range of systems, including activated sludge bioreactors, the microbial residence time (MRT) has been previously shown to shape the microbial community composition. However, the physiological and ecological mechanisms driving this influence have remained unclear. Here, this relationship is explored by analyzing an activated sludge system fed with municipal wastewater. Using a model designed in this study based on Monod-growth kinetics, longer MRTs were shown to increase the range of growth parameters that enable persistence, resulting in increased richness and diversity in the modeled community. In laboratory experiments, six sequencing batch reactors treating domestic wastewater were operated in parallel at MRTs between 1 and 15 days. The communities were characterized using both 16S ribosomal RNA and non-target messenger RNA sequencing (metatranscriptomic analysis), and model-predicted monotonic increases in richness were confirmed in both profiles. Accordingly, taxonomic Shannon diversity also increased with MRT. In contrast, the diversity in enzyme class annotations resulting from the metatranscriptomic analysis displayed a non-monotonic trend over the MRT gradient. Disproportionately high abundances of transcripts encoding for rarer enzymes occur at longer MRTs and lead to the disconnect between taxonomic and functional diversity profiles.
微生物生态学中的一个遗留挑战是理解环境微生物群落中观察到的丰富度和多样性的决定因素。在一系列系统中，包括活性污泥生物反应器，先前已经表明微生物停留时间（MRT）会影响微生物群落组成。然而，驱动这种影响的生理和生态机制仍不清楚。本研究通过分析以城市污水为食的活性污泥系统来探索这种关系。本研究设计了一个基于 Monod 生长动力学的模型，结果表明较长的 MRT 会增加能够持续存在的生长参数范围，从而增加模型社区的丰富度和多样性。在实验室实验中，以 1 到 15 天的 MRT 平行运行六个处理家庭污水的序批式反应器。使用 16S 核糖体 RNA 和非靶向信使 RNA 测序（宏转录组分析）对群落进行了表征，并在两个图谱中均证实了模型预测的丰富度单调增加。因此，Shannon 分类多样性也随着 MRT 的增加而增加。相比之下，来自宏转录组分析的酶类注释多样性在 MRT 梯度上呈现出非单调趋势。在较长的 MRT 下，编码罕见酶的转录本的丰度不成比例地高，导致分类和功能多样性图谱之间的脱节。
