Microbial consortium enriched at the cathode of a solar microbial fuel cell
The objective of this project is to study a microbial biocathode consortium enriched at the U.S. Naval Research Laboratory's Center for Bio/Molecular Science & Engineering. The initial inoculum for the solar microbial fuel cell was seawater collected near Rutgers, NJ, and the community has subsequently been maintained electroautotrophically via serial transfers on cathodes poised at 310 mV vs. SHE. This microbial consortium contains autotrophic organisms which can use a cathode as an electron donor and O2 as an electron acceptor, and has electrochemical properties potentially useful in bioenergy applications including microbial electrosynthesis and microbial fuel cell technology. System biology approaches will be used to identify functional genes that are relevant for bioenergy production, such as fixing CO2 as sole carbon source, electrosynthesis, O2 tolerance, etc. Several heterotrophic constituents have been isolated in pure culture, and have been sequenced by either Illumina or PacBio technologies. Furthermore, closed genomes and methylation data were obtained from PacBio sequencing of metagenomic DNA. Metagenomic libraries generated from eight biological replicates of an enriched biocathode microbial community were sequenced at 2x100 base pairs (bp) (paired-end reads) using an Illumina HiSeq 2000. The reads were assembled using either IDBAUD or Ray. The ideal k-mer length and node coverage were selected based on which gave results most similar to de novo sequencing of isolated bacterial cultures from the enriched community (Marinobacter sp. strain CP1 and Labrenzia sp. strain CP4). Metatranscriptomic libraries were generated from four reactors inoculated with the same inoculum were grown at a set potential of 310 mV SHE until current density stabilized, cyclic voltammetry was recorded, and then two of them were set at a more positive potential (470 mV) and two remained at 310 mV for 48 hours before samples were harvested for RNA extraction. This experiment was repeated with four more reactors inoculated with a new cell suspension from the same source electrode for a total of four biological replicates at each potential.