Exploring Extracellular Electron Transfer in Hyperthermophiles for Electrochemical Energy Conversion

Abstract

Hyperthermophiles are microorganisms that thrive in extremely hot environment from 80 °C and upwards. They are the most primitive organisms evolved to survive in the early uninhabitable earth. We explored the extracellular electron transfer ability of a hyperthermophilic archaeon called Pyrococccus furiosus (Pf). Pf is an aquatic anaerobe that grows optimally at 100 °C using a wide range of substrates such as carbohydrates and peptides. Their ability to reduce the extracellular oxidants such as insoluble Fe(III) oxide and soluble Fe(III) citrate has been investigated. Pf reduced Fe(III) oxide during its growth at 90 °C and the Pf culture re-suspended in MOPS buffer (pH 7.5) was found to reduce Fe(III) citrate significantly using H2 as an electron donor. Further, Pf grown in two-chamber microbial fuel cell (MFC) at 90 °C was found to show a significant electrochemical response compared to the un-inoculated control MFC. The proof of concept study reported here reveals the potential of Pf to generate electricity in MFCs at high temperature locations such as hydrothermal vents.