Ferroplasma acidiphilum gen. nov., sp. nov., an acidophilic, autotrophic, ferrous-iron-oxidizing, cell-wall-lacking, mesophilic member of the Ferroplasmaceae fam. nov., comprising a distinct lineage of the Archaea.

An isolate of an acidophilic archaeon, strain YT, was obtained from a bioleaching pilot plant. The organism oxidizes ferrous iron as the sole energy source and fixes inorganic carbon as the sole carbon source. The optimal pH for growth is 1.7, although growth is observed in the range pH 1.3 to 2.2. The cells are pleomorphic and without a cell wall. 16S rRNA gene sequence analysis showed this strain to cluster phylogenetically within the order 'Thermoplasmales' sensu Woese, although with only 89.9 and 87.2% sequence identity, respectively, to its closest relatives, Picrophilus oshimae and Thermoplasma acidophilum. Other principal differences from described species of the 'Thermoplasmales' are autotrophy (strain YT is obligately autotrophic), the absence of lipid components typical of the ' Thermoplasmales' (no detectable tetraethers) and a lower temperature range for growth (growth of strain YT occurs between 15 and 45 degrees C). None of the sugars, amino acids, organic acids or other organic compounds tested was utilized as a carbon source. On the basis of the information described above, the name Ferroplasma acidiphilum gen. nov., sp. nov. is proposed for strain YT within a new family, the Ferroplasmaceae fam. nov. Strain YT is the type and only strain of F. acidiphilum. This is the first report of an autotrophic, ferrous-iron-oxidizing, cell-wall-lacking archaeon.

[Sulfurococcus yellowstonii sp. nov/--a new species of iron- and sulfur-oxidizing thermoacidophilic Archaeobacterium]. / Sulfurococcus yellowstonii sp. nov.--novyi vid zhelezo- i serookisliaiushchei termoatsidofil'noi arkhebakterii.

A spheric thermoacidophilic sulphur-oxidizing archaebacterium (strain Str6kar) has been isolated from the hydrotherm of the Yellowstone National Park (USA). The isolate is a facultative autotroph. The strain Str6kar oxidizes elemental sulfur, ferrous sulfate and sulphide minerals, it is capable of using some organic compounds. The isolate grows at the temperature of 40-80 degrees. The content of GC-pairs in the DNA of the bacterium is 44.6 mol%. The level of homology of the isolates DNA for the Str6kar and Sulfurococcus mirabilis is 12-15%, for Str6kar and Metallosphaera sedula-0.7-7%. According to the structure of the 5s rRNA, the described bacteria are similar to S. mirabilis. Basing on morphological, physiological and molecular-genetical features, this archaeobacterium can be presented as a new species of the genus of Sulfurococcus-S. yellowstonii sp. nov.