Scanning electron micrograph of cells of strain H-5T. Bar = 1.0 micron. - Source:2Fermentation
Geothrix is an iron-reducing anaerobic bacterium, described from an isolate sourced from a contaminated aquifer 2. Cells are rod shaped and occur singly or in short chains 2. The sole species of the genus Geothrix fermentans uses acetate, propionate, lactate, fumarate and palmitate as alternative electron donors. Fe(III) serves as sole electron acceptor, but growth can also occur with nitrate, Mn(IV), fumarate and the humic acid analogue 2,6-anthraquinone disulfonate as alternative electron acceptors. Can also grow fermentatively on organic acids, such as fumarate and citrate, yielding acetate and succinate as fermentation products. Produces an electron shuttle for reducing Fe(III) in the external environment. Geothrix's in situ activity in activated sludge has not been studied.
 Coates, Ellis, Gaw, Lovley (1999): Geothrix fermentans gen. nov., sp. nov., a novel Fe(III)-reducing bacterium from a hydrocarbon-contaminated aquifer. Int. J. Syst. Bacteriol. 49 Pt 4 (): 1615-22. doi:10.1099/00207713-49-4-1615