The Right Tool for the Job: Genetic, Genomic, and Evolutionary Studies of Organisms Suited for Industrial Strength Bioelectrocatalysis

When Microbial Fuel Cells first harnessed metal-reducing bacteria fifteen years ago, model organisms with genetic systems and sequenced genomes were rare. Freshwater aquifers were active sites of research due to interest in heavy metal and petroleum bioremediation, low-strength wastewater was a common source of microbial inocula, and electrode potentials were a consequence of internal device resistance rather than potentiostat control. Thus we have a poor understanding of the microbiological and biochemical diversity capable of catalyzing bioelectrical reactions at conductivities and temperatures typical for industrial operation and desalination. We need model organisms which operate at higher salt concentrations, increased buffer capacities, raised temperatures, and controlled reduction potentials. This talk will discuss new genome sequences which reveal unexpected diversity in metal-reducing bacteria, not just from the Proteobacteria, but also less well-studied groups representing Gram Positive, Acidobacteria and Bacteroidetes/Chlorobi phyla. New genetic techniques that utilize deep sequencing can ask what mechanisms are important in these difficult to cultivate organisms, as well as in mixed communities and biofilm environments, accelerating discovery of proteins controlling their respiration in electrical devices. Such comparisons show that electron transfer strategies, redox potential preferences, electron shuttles, and conductivity behaviors are not well conserved, further underscoring a need to revisit basic research in a wider array of bacteria. Finally, we will show that because bioelectrochemical systems are artificial environments, they can be powerfully selective for growth of bacteria with particular strategies, and evolution of new variants, although the rules governing natural selection in biofilms are unique. Understanding the environments created by electrodes, and the organisms we need to favor to achieve a desired outcome, will be essential for successful long term operation.