Thermovibrio ruber gen. nov., sp. nov., an extremely thermophilic, chemolithoautotrophic, nitrate-reducing bacterium that forms a deep branch within the phylum Aquificae

Abstract

A novel, extremely thermophilic, chemolithoautotrophic bacterium was isolated from the submarine hydrothermal system off the beach of Lihir Island, Papua New Guinea. Cells of the organism were curved rods of about 1.5-3 microm in length and 0.5-0.8 microm in width. The bacterium grew within the temperature range 50-80 degrees C (optimum around 75 degrees C) and was an obligate anaerobe. Molecular hydrogen was used as the sole electron donor by the bacterium, and nitrate or elemental sulfur served as electron acceptors, producing ammonium or H2S, respectively. Complex organic substrates stimulated growth of the bacterium, but they could not be used as the sole energy source. Based on 16S-rDNA-based phylogenetic analyses and on physiological, biochemical and structural characteristics, the novel organism was found to represent a novel genus for which the name Thermovibrio is proposed. This novel genus, together with Desulfurobacterium thermolithotrophum, may represent a new order within the phylum Aquificae. Since cell pellets of the novel bacterium had an intense red colour, the name Thermovibrio ruber is proposed for the novel organism. The type strain of Thermovibrio ruber gen. nov., sp. nov. is ED11/3LLKT (= DSM 14644T = JCM 11468T).