A facultative aerobe resembling Sulfolobus also lives in acidic solfataric springs. This organism, named Acidianus, differs from Sulfolobus most clearly by its ability to grow anaerobically. Remarkably, Acidianus is able to use S0 in both its aerobic and anaerobic metabolism. Under aerobic conditions the organism uses S0 as an electron donor, oxidizing S0 to H2SO4. Anaerobically, Acidianus uses S0 as an electron acceptor (with H2 as electron donor) forming H2S as the reduced product. Thus, the metabolic fate of S0 in cultures of Acidianus depends on the presence or absence of O2. Lke Sulfolobus, Acidianus is roughly spherical in shape but is not as lobed. It grows at temperatures from 65°C up to a maximum of 95°C, with an optimum of about 90°C.
Taken from the text Brock Biology of Microorganisms (10th ed.). Madigan, M.T., Martinko, J.M., and Parker, J. 2003. Prentice Hall. 464-465p.