BioTechnology Institute, University of Minnesota, St. Paul, MN, United States.
Biology Program, University of Minnesota, St. Paul, MN, United States.
Sci Total Environ. 2015 Apr 1;511:461-8. doi: 10.1016/j.scitotenv.2014.12.069. Epub 2015 Jan 6.
Taxonomic compositions of freshwater bacterial communities have been well-characterized via metagenomic and amplicon-based approaches, especially next-generation sequencing. However, functional diversity of these communities remains less well-studied. Various anthropogenic sources are known to impact the bacterial community composition in freshwater riverine systems and potentially alter functional diversity. In this study, high-throughput functional screening of large (~10,000 clones) fosmid libraries representing communities in the Upper Mississippi River revealed low frequencies of resistance to heavy metals in the following order: Mn2+>Cr3+>Zn2+>Cd2+>Hg2+. No resistance to Cu2+ was detected. Significant, but weak, correlations were observed between resistance frequencies of Cd and Cr with developed land cover (r2=0.08, P=0.016 and r=0.07, P=0.037, respectively). While discriminant function analyses further supported these associations, redundancy analysis further indicated associations with forested land cover and greater resistance to Hg and Zn. Nutrient and metal ion concentrations and abundances of bacterial orders were poorly correlated with heavy metal resistance, except for an association of Pseudomonadales abundance and resistance to Hg and Zn. Taken together, results of this study suggest that allochthonous bacteria contributed from specific land cover types influence the patterns of metal resistance throughout this river.
通过宏基因组学和基于扩增子的方法（尤其是下一代测序），已经很好地描述了淡水细菌群落的分类组成。然而，这些群落的功能多样性研究得还不够充分。已知各种人为来源会影响淡水河流系统中的细菌群落组成，并可能改变功能多样性。在这项研究中，高通量筛选代表密西西比河上游群落的大型 (~10,000 个克隆) fosmid 文库，揭示了以下重金属的抗性频率较低：Mn2+>Cr3+>Zn2+>Cd2+>Hg2+。未检测到对 Cu2+的抗性。与开发土地覆盖（r2=0.08，P=0.016 和 r=0.07，P=0.037）相比，Cd 和 Cr 的抗性频率之间存在显著但较弱的相关性。判别函数分析进一步支持了这些关联，冗余分析进一步表明与森林土地覆盖和对 Hg 和 Zn 的更高抗性有关。除了假单胞菌属丰度与 Hg 和 Zn 抗性之间存在关联外，重金属抗性与养分和金属离子浓度以及细菌目丰度的相关性较差。总的来说，这项研究的结果表明，来自特定土地覆盖类型的异源细菌会影响整个河流的金属抗性模式。
