The Genus Sulfolobus

Abstract

Our work on Sulfolobus originally arose out of a determination to find a natural habitat for Thermoplasma. As discussed in the previous chapter, Thermoplasma was originally discovered as an acidophilic thermophile living in self-heated coal refuse piles. As this seemed an unlikely permanent habitat of the organism, I naturally thought about the hot, acid environments of Yellowstone. My determination to find Thermoplasma in Yellowstone was strengthened by an observation that Gary Darland had made during his attempt to define the upper temperature for life in acidic environments (see Brock and Darland, 1970). He had immersed microscope slides in the effluents of a number of acid, thermal streams, and by a quantification of the organisms that developed on the slides he could define the upper temperature limits. At that time, we were aware only of rod-shaped and filamentous bacteria, but in several of the effluents, at temperatures at which rods and filaments did not appear, there were odd-shaped spherical structures. Since most of these acid streams are sulfur-rich, I interpreted these structures as some sort of amorphous sulfur deposit. In retrospect, I should have realized that they were living organisms, since they not only were phase dark, but appeared on the slides in a distribution that could have been interpreted as microcolonies.