SULFOPHOBOCOCCUS ZILLIGII GEN-NOV, SPEC NOV A NOVEL HYPERTHERMOPHILICARCHAEUM ISOLATED FROM HOT ALKALINE SPRINGS OF ICELAND

The phenotypic and genotypic properties of a new coccoid hyperthermoph ilic archaeum (3-5 mu m in diameter) which has been isolated from a ho t alkaline spring near Hveragerdi, Iceland, are described. The new str ain is a strict anaerobe and grows fermentatively on yeast extract. Gr owth is inhibited by elemental sulfur. Under laboratory conditions, gr owth is observed between 70 and 95 degrees C at pH 6.5 to 8.5. Its mem brane lipids consist exclusively of dibiphytanyldiglycerol tetraethers . Respiratory lipoquinones are absent. The G+C content of the DNA has been determined to be 54.7 +/- 0.8 mol%. On the basis of its 16S rDNA sequence the strain is affiliated to the crenarchaeotal branch of Arch aea. The next relatives are Desulfurococcus mobilis (4.5% dissimilarit y) and Pyrodictium occultum (7.0% dissimilarity). Due to the phenotypi c and genotypic properties of this new isolate which distinguish it fr om other currently known Archaea, we propose to placing it in a new ge nus, Sulfophobococcus with the first species S. zilligii in honour of WOLFRAM ZILLIG, a pioneer in the field of hyperthermophilic Archaea.