A Microbial Biorealm page on the genus Sulfolobus
Higher order taxa:
Archaea; Crenarchaeota; Thermoprotei; Sulfolobales; Sulfolobaceae
Sulfolobus shibatae, S. solfataricus P2, S. tokodaii sp. nov. (f. Sulfolobus sp. strain 7)
Description and Significance
Sulfolobales grow in terrestrial volcanic hot springs with optimum growth occurring at pH 2-3 and a temperature of 75-80oC. Analysis of the genomes can provide information on the thermostability of proteins as well as characteristics of cells living in an acidic environment. There can also be industrial applications for these microbes. For example, S. tokodaii strain 7 is known to oxidize hydrogen sulfide to sulfate intracellularly, which has been used to treat industrial waste water.
The archaeon Sulfolobus solfataricus has a circular chromosome that consists of 2,992,245 bp. Another sequenced species, S. tokodaii has a circular chromosome as well but is slightly smaller with 2,694,756 bp. Both species lack the genes ftsZ and minD, which has been characteristic of sequenced crenarchaeota. They also code for citrate synthase and two subunits of 2-oxoacid:ferredoxin oxidoreductase, which plays the same role as alpha-ketoglutarate dehydrogenase in the TCA cycle. This indicates that Sulfolobus has a TCA cycle system similar to that found in mitochondria of eukaryotes. Other genes in the respiratory chain which partake in the production of ATP were not similar to what is found in eukaryotes. Cytochrome c is one such example that plays an important role in electron transfer to oxygen in eukaryotes. This was also found in A. pernix K1. Since this step is important for an aerobic microorganism like Sulfolobus, it probably uses a different molecule for the same function or has a different pathway.
Cell Structure and Metabolism
Sulfolobus can grow either lithoautotrophically by oxidizing sulfur, or chemoheterotrophically using sulfur to oxidize simple reduced carbon compounds. Heterotrophic growth has only been observed, however, in the presence of oxygen. The principle metabolic pathways are a glycolytic pathway, a pentose phosphate pathway, and the TCA cycle.
All Archaea have lipids with ether links between the head group and side chains, making the lipids more resistant to heat and acidity than bacterial and eukaryotic ester-linked lipids. The Sulfolobales are known for unusual tetraether lipids.In Sulfolobales, the ether-linked lipids are joined covalently across the "bilayer," making tetraethers. Technically, therefore, the tetraethers form a monolayer, not a bilayer. The tetraethers help Sulfolobus species survive extreme acid as well as high temperature.
S. solfataricus has been found in different areas including Yellowstone National Park, Mount St. Helens, Iceland, Italy, and Russia to name a few. Sulfolobus is located almost wherever there is volcanic activity. They strive in environments where the temperature is about 80oC with a pH at about 3 and sulfur present. Another species, S. tokodaii, has been located in an acidic spa in Beppu Hot Springs, Kyushu, Japan. Sediments from ~90m below the seafloor on the Peruvian continental margin are dominated by inact archaeal teraethers, and a significant fraction of the community is sedimentary archaea taxonomically linked to the crenarchaeal Sulfolobales (Sturt, et al, 2004).
The Sulfolobus viruses are temperate or permanent lysogens. Permanent lysogens differ from lysogenic bacterial phages in that the host cells are not lysed after the induction of Fuselloviridae production and eventually return to the lysogenic state. They are also unique in the sense that the genes encoding the structural proteins of the virus are constantly transcribed and DNA replication appears to be induced. The viruses infecting archaea like Sulfolobus have to use a strategy to escape prolonged direct exposure to the type of environment their host lives in, which may explain some of their unique properties.
H. F.Sturt, R. E. Summons, K. Smith, M. Elvert. and K.-U. Hinrichs. 2004. Intact polar membrane lipids in prokaryotes and sediments deciphered by high performance liquid chromatography/electrospray ionization multistage mass spectrometry—new biomarkers for biogeochemistry and microbial ecology. Rapid Commun. Mass Spectrom. 2004:617–628.
Kawarabayasi et al. 2001. Complete Genome Sequence of an Aerobic Thermoacidophilic Crenarchaeon, Sulfolobus tokodaii strain 7. DNA Research 8:123-140.
Prangishvili D., K. Stedman, and W. Zillig. 2001. Viruses of the extremely thermophilic archaeon Sulfolobus. TRENDS in Microbiology 9 :39-43.
She et al. 2001. The complete genome of the crenarchaeon Sulfolobus solfataricus P2. PNAS 98:7835-7840.
Suzuki et al. 2002. Sulfolobus tokodaii sp. nov. (f. Sulfolobus sp. strain 7), a new member of the genus Sulfolobus isolated from Beppu Hot Springs, Japan. Extremophiles 6:39-44. Abstract