Bier Raven L, Voss Kristofor A, Bernhardt Emily S
Department of Biology, Duke University, Durham, NC, USA.
Nicholas School of the Environment, Duke University, Durham, NC, USA.
ISME J. 2015 Jun;9(6):1378-90. doi: 10.1038/ismej.2014.222. Epub 2014 Dec 12.
Microbial community composition and diversity change along chemical gradients, leading to the expectation that microbial community information might provide new gradient characterizations. Here we examine stream bacteria composition and diversity along a strong chemical gradient in Central Appalachian streams. Coal mining in the region generates alkaline mine drainage (AlkMD), causing dramatic increases in conductivity, alkalinity, sulfate and metals sufficient to degrade stream macrobiota communities throughout the ecoregion. In this study, we examined the relationship between water and biofilm chemistry and biofilm bacteria taxonomic composition in streams where active and reclaimed surface coal mines occupied 0-96% of watershed surface area. We incubated wood veneers in each stream site for 4 months to develop biofilms on similar substrates. We sampled water chemistry at the time of deployment and collection, and after 1 month. Following incubation, we collected biofilms for microbial and chemical characterization. Microbial composition was determined by pyrosequencing 16S rRNA amplicons. Biofilm subsamples were analyzed by inductively coupled plasma mass spectrometry to determine metal concentrations. Our results show that microbial community composition differed significantly between AlkMD-exposed and AlkMD-unexposed sites, and that compositional dissimilarity increased with AlkMD loading. Diversity was not correlated with pH or extent of upstream mining, but instead correlated with biofilm concentrations of Cd, Mn, Zn and Ni. Within mined sites, the extent of upstream mining was negatively correlated with taxonomic richness. Despite major compositional shifts, functional capacity predicted with PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) correlated with mining in only 3 of 43 level-2 KEGG (Kyoto Encyclopedia of Genes and Genomes) Orthology groups.
微生物群落组成和多样性会随着化学梯度而变化，这使得人们期望微生物群落信息可能提供新的梯度特征描述。在此，我们研究了阿巴拉契亚中部溪流中沿着强烈化学梯度的细菌组成和多样性。该地区的煤矿开采产生碱性矿井排水（AlkMD），导致电导率、碱度、硫酸盐和金属含量急剧增加，足以使整个生态区域的溪流大型生物群落退化。在本研究中，我们研究了活跃和已复垦的露天煤矿占据流域表面积0 - 96%的溪流中，水和生物膜化学与生物膜细菌分类组成之间的关系。我们在每个溪流站点将木皮孵育4个月，以便在类似的基质上形成生物膜。我们在放置和收集时以及1个月后对水化学进行了采样。孵育后，我们收集生物膜进行微生物和化学特征分析。通过对16S rRNA扩增子进行焦磷酸测序来确定微生物组成。通过电感耦合等离子体质谱分析生物膜子样本以确定金属浓度。我们的结果表明，暴露于AlkMD和未暴露于AlkMD的站点之间微生物群落组成存在显著差异，并且组成差异随着AlkMD负荷的增加而增大。多样性与pH值或上游采矿程度无关，而是与生物膜中镉、锰、锌和镍的浓度相关。在采矿站点内，上游采矿程度与分类丰富度呈负相关。尽管有重大的组成变化，但用PICRUSt（通过重建未观察状态对群落进行系统发育研究）预测的功能能力仅在43个二级KEGG（京都基因与基因组百科全书）直系同源组中的3个中与采矿相关。
