Geothrix fermentans gen. nov., sp nov., a novel Fe(III)-reducing bacteriumfrom a hydrocarbon-contaminated aquifer

In an attempt to understand better the micro-organisms involved in anaerobi c degradation of aromatic hydrocarbons in the Fe(III)-reducing zone of petr oleum-contaminated aquifers, Fe(III)-reducing micro-organisms were isolated from contaminated aquifer material that had been adapted for rapid oxidati on of toluene coupled to Fe(III) reduction. One of these organisms, strain H-5(T), was enriched and isolated on acetate/Fe(III) medium. Strain H-5T is a Gram-negative strict anaerobe that grows with various simple organic aci ds such as acetate, propionate, lactate and fumarate as alternative electro n donors with Fe(III) as the electron acceptor. In addition, strain H-5T al so oxidizes long-chain fatty acids such as palmitate with Fe(III) as the so le electron acceptor. Strain H-5T can also grow by fermentation of citrate or fumarate in the absence of an alternative electron acceptor. The primary endproducts of citrate fermentation are acetate and succinate. In addition to various forms of soluble and insoluble Fe(III), strain H-5T grows with nitrate, Mn(IV), fumarate and the humic acid analogue 2,6-anthraquinone dis ulfonate as alternative electron accepters. As with other organisms that ca n oxidize organic compounds completely with the reduction of Fe(III), cell suspensions of strain H-5T have absorbance maxima indicative of a c-type cy tochrome(s). It is proposed that strain H-5T represents a novel genus in th e Holophaga-Acidobacterium phylum and that it should be named Geothrix ferm entans sp. nov., gen. nov.