Viral diversity and host associations in microbial electrolysis cells.

In microbial electrolysis cells (MECs), microbial communities catalyze conversions between dissolved organic compounds, electrical energy, and energy carriers such as hydrogen and methane. Bacteria and archaea, which catalyze reactions on the anode and cathode of MECs, interact with phages; however, phage communities have previously not been examined in MECs. In this study, we used metagenomic sequencing to study prokaryotes and phages in nine MECs. A total of 852 prokaryotic draft genomes representing 278 species, and 1476 phage contigs representing 873 phage species were assembled. Among high quality prokaryotic genomes (>95% completion), 55% carried a prophage, and the three spp. that dominated the anode communities all carried prophages. , one of the bacteria dominating the anode communities, carried a CRISPR spacer showing evidence of a previous infection by a phage present in the liquid of some MECs. spp. and an sp., which dominated the cathodes, had several associations with spp. The results of this study show that phage communities in MECs are diverse and interact with functional microorganisms on both the anode and cathode.