Sulfolobus: A new genus of sulfur-oxidizing bacteria living at low pH and high temperature

Summary

Sulfolobus is a new genus of bacteria characterized as follows: 1. generally spherical cells producing frequent lobes; 2. facultative autotrophy with growth on sulfur or on a variety of simple organic compounds; 3. unusual cell wall structure devoid of peptidoglycan; 4. acidophilic, pH optimum of 2–3 and range from 0.9–5.8; 5. thermophilic with temperature optimum of 70–75°C and range from 55–80°C (one strain grew at 85°C). The DNA base composition of five strains was determined by cesium chloride density gradient centrifugation and found to be 60–68% guanine plus cytosine. Sulfolobus apparently has no close relationship with any previously described bacteria, either heterotrophic or autrotrophic. Techniques are presented for distinguishing Sulfolobus from Thermoplasma, another genus of acidophilic thermophilic spherically shaped organisms. Sulfolobus has been isolated from a variety of natural acidic thermal habitats, both terrestrial and aquatic. Most isolations have been from habitats in Yellowstone National Park, but strains were also isolated from Italy, Dominica and El Salvador. It is suggested that Sulfolobus may be an important geochemical agent in the production of sulfuric acid from sulfur in high temperature hydrothermal systems.