A novel ecological role of the Firmicutes identified in thermophilic microbial fuel cells.

TitleA novel ecological role of the Firmicutes identified in thermophilic microbial fuel cells.
Publication TypeJournal Article
Year of Publication2008
AuthorsWrighton KC, Agbo P, Warnecke F, Weber KA, Brodie EL, DeSantis TZ, Hugenholtz P, Andersen GL, Coates JD
JournalThe ISME journal
Date Published2008 Nov
KeywordsBioelectric Energy Sources, DNA, Bacterial, DNA, Ribosomal, Electricity, Genes, rRNA, Gram-Positive Bacteria, Hot Temperature, Microarray Analysis, Molecular Sequence Data, Phylogeny, RNA, Bacterial, RNA, Ribosomal, 16S, Sequence Analysis, DNA, Sequence Homology, Nucleic Acid

Significant effort is currently focused on microbial fuel cells (MFCs) as a source of renewable energy. Most studies concentrate on operation at mesophilic temperatures. However, anaerobic digestion studies have reported on the superiority of thermophilic operation and demonstrated a net energy gain in terms of methane yield. As such, our studies focused on MFC operation and microbiology at 55 degrees C. Over a 100-day operation, these MFCs were stable and achieved a power density of 37 mW m(-2) with a coulombic efficiency of 89%. To infer activity and taxonomic identity of dominant members of the electricity-producing community, we performed phylogenetic microarray and clone library analysis with small subunit ribosomal RNA (16S rRNA) and ribosomal RNA gene (16S rDNA). The results illustrated the dominance (80% of clone library sequences) of the Firmicutes in electricity production. Similarly, rRNA sequences from Firmicutes accounted for 50% of those taxa that increased in relative abundance from current-producing MFCs, implying their functional role in current production. We complemented these analyses by isolating the first organisms from a thermophilic MFC. One of the isolates, a Firmicutes Thermincola sp. strain JR, not only produced more current than known organisms (0.42 mA) in an H-cell system but also represented the first demonstration of direct anode reduction by a member of this phylum. Our research illustrates the importance of using a variety of molecular and culture-based methods to reliably characterize bacterial communities. Consequently, we revealed a previously unidentified functional role for Gram-positive bacteria in MFC current generation.

Alternate JournalISME J