International Journal of Systematic and Evolutionary Microbiology, Vol 52, 719-728, Copyright © 2002 by Society for General Microbiology

Geoglobus ahangari gen. nov., sp. nov., a novel hyperthermophilic archaeon capable of oxidizing organic acids and growing autotrophically on hydrogen with Fe(III) serving as the sole electron acceptor

K. Kashefi, J. M. Tor, D. E. Holmes, C. V. Gaw Van Praagh, A. L. Reysenbach and D. R. Lovley
Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA

A novel, regular to irregular, coccoid-shaped, anaerobic, Fe(III)-reducing micro-organism was isolated from the Guaymas Basin hydrothermal system at a depth of 2000 m. Isolation was carried out with a new technique using Fe(III) oxide as the electron acceptor for the recovery of colonies on solid medium. The isolate, designated strain 234(T), was strictly anaerobic and exhibited a tumbling motility. The cells had a single flagellum. Strain 234(T) grew at temperatures between 65 and 90 degrees C, with an optimum at about 88 degrees C. The optimal salt concentration for growth was around 19 g l(-1). The isolate was capable of growth with H(2) as the sole electron donor coupled to the reduction of Fe(III) without the need for an organic carbon source. This is the first example of a dissimilatory Fe(III)-reducing micro-organism capable of growing autotrophically on hydrogen. In addition to molecular hydrogen, strain 234(T) oxidizes pyruvate, acetate, malate, succinate, peptone, formate, fumarate, yeast extract, glycerol, isoleucine, arginine, serine, glutamine, asparagine, stearate, palmitate, valerate, butyrate and propionate with the reduction of Fe(III). This isolate is the first example of a hyperthermophile capable of oxidizing long-chain fatty acids anaerobically. Isolate 234(T) grew exclusively with Fe(III) as the sole electron acceptor. The G+C content was 58.7 mol%. Based on detailed analysis of its 16S rDNA sequence, G+C content, distinguishing physiological features and metabolism, strain 234(T) is proposed to represent a novel genus within the Archaeoglobales. The name proposed for strain 234(T) is Geoglobus ahangari gen. nov., sp. nov.