Sulfolobus solfataricus

Sulfolobus solfataricus
Scientific classification
Domain:	Archaea
Kingdom:	Crenarchaeota
Phylum:	Crenarchaeota
Class:	Thermoprotei
Order:	Sulfolobales
Family:	Sulfolobaceae
Genus:	Sulfolobus
Species:	S. solfataricus
Binomial name
Sulfolobus solfataricus Stetter and Zillig 1980

Sulfolobus solfataricus is a species of thermophilic archaeon.

It was first isolated and discovered in the Solfatara volcano which it was subsequently named after. However, these organisms are not isolated to volcanoes but are found all over the world in places such as hot springs. The species grows best in temperatures around 80° Celsius, a pH level between 2 to 4, and enough sulfur for solfataricus to metabolize in order to gain energy. These conditions qualify it as an extremophile and it is specifically known as a thermoacidophile because of its preference to high temperatures and low pH levels. It usually has a spherical cell shape and it makes frequent lobes. Being an autotroph it receives energy from growing on sulfur or even a variety of organic compounds.

Currently, it is the most widely studied organism that is within the Crenarchaeota branch. Solfataricus are researched for their methods of DNA replication, cell cycle, chromosomal integration, transcription, RNA processing, and translation. All the data points to the organism having a large percent of archaeal-specific genes, which showcases the differences between the three types of microbes: archaea, bacteria, and eukarya.

Genome sequencing results

Scientists from the European Union and Canada managed to completely sequence the genome of solfataricus in 2001. On a single chromosome, there are 2,992,245 base pairs which encode for 2,977 proteins and copious RNAs. For the encoded proteins, 40% were found to be archaeal-specific, 12% bacteria-specific, and 2.3% eukarya-specific, while the last one-third proteins currently have no homologs in common with other sequenced genes. The genome has a wide range of diversity as it has 200 different insertion sequence elements. This is coupled with lengthy groupings of routinely spaced tandem repeats. The study favors ferredoxin as the major metabolic electron carrier. This contrasts with bacteria and eukarya because they rely on NADH for their functions. Solfataricus has strong eukaryal features coupled with many uniquely archaeal-specific abilities. The results of the findings came from the varied methods of their DNA mechanisms, cell cycles, and transitional apparatus. Overall, the study was a prime example of the differences found in crenarchaea and euryarchaea.

DNA transfer

Exposure of Sulfolobus solfataricus to the DNA damaging agents UV-irradiation, bleomycin or mitomycin C induces cellular aggregation. Other physical stressors, such as changes in pH or temperature shift, do not induce aggregation, suggesting that induction of aggregation is caused specifically by DNA damage. Ajon et al. showed that UV-induced cellular aggregation mediates chromosomal marker exchange with high frequency. Recombination rates exceeded those of uninduced cultures by up to three orders of magnitude. Frols et al. and Ajon et al. hypothesized that the UV-inducible DNA transfer process and subsequent homologous recombinational repair represents an important mechanism to maintain chromosome integrity. This response may be a primitive form of sexual interaction, similar to the more well-studied bacterial transformation that is also associated with DNA transfer between cells leading to homologous recombinational repair of DNA damage.

Further reading

• Brock, T., Brock, K., Belly, R., and Weiss, R. "Sulfolobus: A new genus of sulfur-oxidizing bacteria living at low pH and high temperature". Archives of Microbiology. 1972. Volume 84. p. 54-68.
• She, Q., Singh, S., Confalonerl, F., et al. "The complete genome of the crenarchaeon Sulfolobus solfataricus P2". Proceedings of the National Academy of Sciences of the United States of America. 2001. Volume 98. p. 7835-7840.
• Wolfram, Z., Stetter, K., Wunderel, S., et al. The Sulfolobus-"Caldariella" group: Taxonomy on the basis of the structure of DNA-dependent RNA polymerases Archives of Microbiology. 1980. Volume 125. p. 259-269.
• Bernstein H and Bernstein C (2013). Evolutionary Origin and Adaptive Function of Meiosis. In Meiosis: Bernstein C and Bernstein H, editors. ISBN 978-953-51-1197-9, InTech, http://www.intechopen.com/books/meiosis/evolutionary-origin-and-adaptive-function-of-meiosis