Department of Zoology, University of Otago, Dunedin, New Zealand.
School of Natural Sciences, Trinity College Dublin, the University of Dublin, Dublin 2, Ireland.
Sci Rep. 2017 Mar 22;7:44657. doi: 10.1038/srep44657.
Disentangling the individual and interactive effects of multiple stressors on microbial communities is a key challenge to our understanding and management of ecosystems. Advances in molecular techniques allow studying microbial communities in situ and with high taxonomic resolution. However, the taxonomic level which provides the best trade-off between our ability to detect multiple-stressor effects versus the goal of studying entire communities remains unknown. We used outdoor mesocosms simulating small streams to investigate the effects of four agricultural stressors (nutrient enrichment, the nitrification inhibitor dicyandiamide (DCD), fine sediment and flow velocity reduction) on stream bacteria (phyla, orders, genera, and species represented by Operational Taxonomic Units with 97% sequence similarity). Community composition was assessed using amplicon sequencing (16S rRNA gene, V3-V4 region). DCD was the most pervasive stressor, affecting evenness and most abundant taxa, followed by sediment and flow velocity. Stressor pervasiveness was similar across taxonomic levels and lower levels did not perform better in detecting stressor effects. Community coverage decreased from 96% of all sequences for abundant phyla to 28% for species. Order-level responses were generally representative of responses of corresponding genera and species, suggesting that this level may represent the best compromise between stressor sensitivity and coverage of bacterial communities.
阐明多种压力源对微生物群落的单独和交互影响是我们理解和管理生态系统的关键挑战。分子技术的进步允许我们在原位和高分类分辨率水平上研究微生物群落。然而，在能够检测多种压力源效应与研究整个群落的目标之间取得最佳折衷的分类水平仍然未知。我们使用模拟小河流的户外中观模型来研究四种农业压力源（养分富化、硝化抑制剂双氰胺（DCD）、细泥沙和流速降低）对溪流细菌（门、目、属和种，用具有 97%序列相似性的操作分类单位表示）的影响。使用扩增子测序（16S rRNA 基因，V3-V4 区）评估群落组成。DCD 是最普遍的压力源，影响均匀度和最丰富的分类群，其次是泥沙和流速。压力源的普遍性在分类水平上相似，较低的水平并不能更好地检测压力源的影响。从丰富的门的所有序列的 96%下降到种的 28%。目水平的反应通常代表相应属和种的反应，这表明该水平可能是压力源敏感性和细菌群落覆盖率之间的最佳折衷。
