Electron shuttle enrichment: freshwater wetland
DNA extraction was performed using the Qiagen PowerSoil DNA Isolation kit according to the manufacturers protocol. All DNA quantitation was performed using the Qubit assay (Invitrogen). PCR was used to amplify the V4 region of the 16S rRNA gene using a modified version of the universal 515F-806R primer pair in order to survey the bacterial and archaeal community in the extracted samples (46). Paired-end amplicons were then sequenced on the Illumina MiSeq platform (151bp x 12bp x 151bp) using customized sequencing primers and procedures as described by Caporaso et al. (47). A total of three sequencing runs (batch 1-3) generated 6.91 million paired-end sequences were generated (31,858  20,617 per amplicon library).