Desulfurolobus ambivalens, gen. nov., sp. nov., an autotrophic Archaebacterium facultatively oxidizing or reducing sulfur

Summary The archaebacterium Desulfurolobus ambivalens gen. nov. sp. nov., family Sulfolobaceae , is an obligate chemolitho-autotroph, facultatively growing by the oxidation with O 2 or the reduction with H 2 of elemental sulfur with CO 2 as sole carbon source. D. ambivalens contains several plasmids, one of which, pSL10, is amplified during anaerobic growth. This amplification is accompanied by the appearance of virus-like particles resembling those described for Sulfolobus spec. B12. A subclone of D. ambivalens not containing the plasmid pSL10 is still able to grow by both sulfur oxidation and sulfur reduction indicating that the plasmid does not harbor genes for chemolithoautotrophic growth. The phylogenetic position of this organism within the Sulfolobaceae and the taxonomy of this group are discussed in the light of molecular evidence.