An archaeum originally misclassified as bacterium: Sulfolobus acidocaldarius

The microbe Sulfolobus acidocaldarius was isolated from a hot spring in Yellowstone National Park in 1972 and originally misclassified as bacterium [1,2]. Thomas D. Brook and his team described the new genus Sulfolobus as sulfur-oxidizing bacteria with generally spherical cells producing frequent lobes—hence the term Sulfolobus. The isolated microbes were further characterized as acidophilic, living at an optimal pH of 2-3 and optimal temperatures of 70-75 °C—hence the epithet acidocaldarius. Microbes thriving at such temperatures are called hyperthermophiles.

About five years later the archaea domain was proposed by Carl Woese and George Fox. Following detailed genome studies, S. acidocaldarius was then taxonomically classified as belonging to the phylum or kingdom  crenarchaeota in the domain archaea. S. acidocaldarius serves now as a model organism for the Crenarchaeota and is used for many studies in archaeal biology [3,4].

Keywords: microbiology, hyperthermophile, crenarchaeon, nomenclature, taxonomy, history.

References and more to explore
[1] T. D. Brook, K. M. Brock, R. T. Belly and R. L. Weiss:  Sulfolobus: A new genus of sulfur-oxidizing bacteria living at pH and high temperature. Archives of Microbiology 1972, 84 (1), pp. 54-68. DOI: 10.1007/BF00408082.
[2] Tim Friend: The Third Domain. The Untold Story of Archaea and the Future of Biotechnology. Joseph Henry Press, Washington, D.C., 2007; pages 110 and 111.
[3]  Microbe Wiki: Sulfolobus acidocaldarius [microbewiki.kenyon.edu/index.php/Sulfolobus_acidocaldarius].
[4] L. Chen et al.: The genome Sulfolobus acidocaldarius, a model organism of the Crenarcheota. Journal of Bacteriology 2005, 187 (14), pp. 4992-4999 [www.ncbi.nlm.nih.gov/pubmed/15995215].