Electricigens are bacteria that can perform extracellular transfer of electrons directly to an insoluble electron acceptor such as an electrode. Electricigenic bacteria can be utilized for a number of beneficial processes including: powering remote sensing devices, bioremediation, the treatment of waste and the production of electrobiocomodities.
The isolation of novel electricigens has predominately taken place from anaerobic environments that include: aqueous sediments, sewage sludge and wastewater enrichments, or from the screening of existing laboratory collections. However, there have been no reported isolation of electricigenic bacteria in pure culture from an Australian origin or from non-aqueous environments such as terrestrial soils. The aim of this project was to isolate an electricigen from a local terrestrial soil.
A sample from the Gresswell Forest Nature Reserve at Latrobe University was enriched for electricigens in a sedimentary microbial fuel cell over 280 days before isolation and purification on insoluble Iron Oxide as a final electron acceptor. Eighteen isolates of differing morphology were selected using the roll tube method. The isolates were characterized for growth with both soluble and insoluble final electron acceptors. The enriched Gresswell Forest microbial community was capable of fully reducing insoluble Fe3+ within 4 days, a rate of 5.1 M d-1, compared to the pure isolates which ranged in Fe3+ reductions rates of 2.9 M d-1 and >6.1 M d-1.
Three of the isolates were found to be capable of using an electrode as a final electron acceptor in pure culture using acetate as a sole carbon source. Isolate MA-F, identified by sequencing as Clostridium saccharolyticum WM1, was shown to produce 150 mV, which is comparable to the model electricigen Geobacter sulfurreducens, which produced 200 mV under comparable conditions.