Population Analysis of Mesophilic Microbial Fuel Cells Fed with Carbon Monoxide

Electricity generation in a microbial fuel cell (MFC) fed with carbon monoxide (CO) has been recently demonstrated; however, the microbial ecology of this system has not yet been described. In this work the diversity of the microbial community present at the anode of CO-fed MFCs was studied by performing denaturing gradient gel electrophoresis (DGGE) and high-throughput sequencing (HTS) analyses. HTS indicated a significant increase of the archaeal genus Methanobacterium and of the bacterial order Clostridiales, notably including Clostridium species, while in both MFCs DGGE identified members of the bacterial genera Geobacter, Desulfovibrio, and Clostridium, and of the archaeal genera Methanobacterium, Methanofollis, and Methanosaeta. In particular, the presence of Geobacter sulfurreducens was identified. Tolerance of G. sulfurreducens to CO was confirmed by growing G. sulfurreducens with acetate under a 100 % CO atmosphere. This observation, along with the identification of acetogens, supports the hypothesis of the two-step process in which CO is converted to acetate by the carboxidotrophic Bacteria and acetate is then oxidized by CO-tolerant electricigenic Bacteria to produce electricity.