A chemoautotrophic and thermophilic microorganism isolated from an acid hot spring

A pleomorphic, acidophilic, and chemoautotrophic microbe is described. The cell is bound by a membrane and a diffuse, amorphous layer. The isolate used either sulfur or iron as a source of energy. Morphological and nutritional similarities as well as corresponding thermophilic and acidophilic requirements suggest a relationship to Sulfolobus. The organism tolerates 80 °C for longer than 2 h, but heat resistance is not attributed to a bacterial spore. The maximum temperature for growth is 70 °C; the minimum about 45 °C.The DNA base composition is 57 ± 3 mole % GC. Yeast extract enhances growth of the isolate on iron and sulfur substrates, but does not significantly enhance the isolate's respiration rate on these same substrates.The isolate requires induction by sulfur or iron for maximum respiration on these substrates, respectively. Optimum oxidation of elemental sulfur occurred at pH 2.0 and gave a [Formula: see text] of 163; oxidation on iron gave a maximum [Formula: see text] of 879.