Sulfolobus solfataricus

Saccharolobus solfataricus is a species of thermophilic archaeon. It was transferred from the genus Sulfolobus to the new genus Saccharolobus with the description of Saccharolobus caldissimus in 2018. 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 and 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. Scientists from the European Union and Canada managed to completely sequence the genome of S. solfataricus in 2001. On a single chromosome, there are 2,992,245 base pairs which encode for 2,977 proteins and copious RNAs. One-third of S. solfataricus encoded proteins have no homologs in other genomes. For the remaining encoded proteins, 40% are specific to Archaea, 12% are shared with Bacteria, and 2.3% are shared with Eukarya. The S. solfataricus 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. Ferredoxin is suspected to act as the major metabolic electron carrier in S. solfataricus. This contrasts with most species within the Bacteria and Eukarya, which generally rely on NADH as the main electron carrier. S. solfataricus has strong eukaryotic 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. Exposure of Saccharolobus 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.