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.
Bibliographical noteFunding Information:
Funding for this study was provided, in part, by grant M.L. 2011, Project 05C from the Minnesota Environment and Natural Resources Trust Fund , as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR). This work was completed using resources at the University of Minnesota Supercomputing Institute. We would also like to thank Cassandra Barrett and Derek Schultz for helping to screen fosmid libraries.
- Amplicon sequencing
- Bacterial community structure
- Fosmid library
- Functional analyses
- Heavy metal resistance
- Mississippi River