The cell membranes of some methane-producing archaea may be electrically conductive.

What is it about?

Membrane electron transport is essential for most cells to grow, including for methane-producing archaea (methanogens). We have extracted and quantified membrane electron carriers from two methanogens, methanophenazine from Methanosarcina acetivorans and Methanosarcina barkeri, as well as quinones from the bacterium E. coli. The concentration of electron carriers in M. acetivorans is consistently high enough to theoretically support conduction or tunneling, but in M. barkeri the concentration of electron carriers is too low, suggesting that electron carriers must diffuse through the lipid membrane. Conduction is faster than diffusion, suggesting that electron transport through the membrane of M. barkeri could be rate-limiting. We then demonstrate that growth rate of the methanogens can be increased by adding exogenous membrane carriers.

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Why is it important?

We demonstrate that there is room in methanogen physiology to increase growth rate and methanogenesis rate. We show that this can be achieved by adding exogenous electron carriers, such as phenazines, which are natural products produced by bacteria. Because methanogens are used worldwide to generate renewable energy (biogas) and contribute to atmospheric methane emissions, our study has implications for bioenergy production and the role of bacterial-methanogen interactions in the global carbon cycle.