Geopsychrobacter electrodiphilus
Geopsychrobacter electrodiphilus is a species of bacteria, the type species of its genus. It is a psychrotolerant member of its family, capable of attaching to the anodes of sediment fuel cells and harvesting electricity by oxidation of organic compounds to carbon dioxide and transferring the electrons to the anode. In microbial communities, "G. electrodiphilus" could be similar to other Geobacteraceae. The community may ferment complex organic matter, thereby breaking up plant matter, for example; "G. electrodiphilus" would then oxidize the fermentation products (especially acetate) to carbon dioxide, whereby a terminal electron acceptor [e.g. iron(III) oxide] would be reduced . At least one strain (A1) can oxidize hydrogen too. Since "G. electrodiphilus" belongs to the Geobateraceae and can transfer electrons to the outside, one could assume that electron transfer to a methane producing archaeon could happen. There is another member of Geobacteraceae, well investigated for its interspecies electron transfer, even to a methanogen. Description. "Geopsychrobacter electrodiphilus" was isolated from the surface of an electrode (anode) of a marine sediment fuel cell. The sediments come from a water depth of 5 meters (Boston Harbor, Massachusetts, near the peninsula World's End). The name "Geopsychrobacter electrodiphilus" means somewhat like "electrode-loving rod  of cold earth" and indicates that the microbe comes from the surface (earth, Geo), copes with cold (), is rod-shaped () and was isolated from electrodes (), which it has voluntarily settled (). Two strains of "Geopsychrobacter electrodiphilus" were isolated (A1 and A2); Strain A1 was determined as the type strain (A1; ATCC BAA-880; DSM 16401; JCM 12469) of the species "Geopsychrobacter electrodiphilus" and as the type strain of the genus. In a study on the cultivation of microbial communities in sludge, where sulphate reducers are likely to benefit, the proportion of "Geopsychrobacter" decreased. An investigation of bacterial diversity in the cold outflow  of an iron oxide-tainted plume of saltwater (Blood Falls, Antarctica) indicated about 11% of cells as "G. electrodiphilus". The plume were identified as a subglacial “ocean”, where coupled biogeochemical processes below the glacier enable microbes to grow in extended isolation, accumulating iron(II) despite the presence of an active sulfur cycle. Interaction with anodes. Holmes "et al." 2004 proposed a likely mechanism for a special microbial fuel cell (sediment fuel cell), to support energy with help of "G. electrodiphilus" and other microbes of a community in marine sediments; based on the article, this imaginary mechanism is summarized here: To explain  their proposal for the process inside the sediment fuel cell, authors referred to previous investigations. Holmes "et al." (2004) did not investigate microbial communities or technical devices; the aim of their investigations was to find organisms that transfer electrons to an electrode and to describe them. The "G. electrodiphilus" strains were able to oxidize acetate, malate, fumarate, and citrate with electron transfer to an electrode poised at +0.52 V (in reference to a standard hydrogen electrode). One key point of harvesting energy using a sediment fuel cell seems to bridge the anaerobic environment of "G. electrodiphilus" and the aerobic water ; the difference in redox potentials can be used. Reduction of poorly crystalline Fe(III) oxide results in the formation of magnetite. It is therefore conceivable that the oligodynamic effect in "Geopsychrobacter" is low and an application with metallic components inside a technical device would be possible.