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 discovered and isolated from the Solfatara volcano (Pisciarelli-Campania, Italy) in 1980 by two German microbiologists Karl Setter and Wolfram Zillig. 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 °C, a pH level between 2 and 4, and with enough sulfur for ''S.'' ''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 for high temperatures and low pH levels. It is also aerobic and heterotropic due to its metabolic system. Being an autotroph, it receives energy by growing on sulfur or even a variety of organic compounds. It usually has a spherical cell shape and it makes frequent lobes.

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

Genome

''Sulfolobus solfataricus'' is the most studied microorganism from a molecular, genetic, and biochemical point of view for its ability to thrive in extreme environments. It can grow easily in the laboratory, and it can exchange genetic material through processes of transformation, transduction, and conjugation.

The major motivation for sequencing these microorganisms is to study the thermostability of proteins that normally denature at a high temperature. The complete sequence the genome of ''S. solfataricus'' was completed in 2001. On a single chromosome, there are 2,992,245 base pairs, which encode 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 Eukaryote; 33% of these proteins are encoded exclusively in ''Sulfolobus''. A high number of open reading frames (ORFs) are highly similar in ''Thermoplasma''.

Small nucleolar RNAs (snoRNAs), already present in eukaryotes, have also been identified in ''S. solfataricus'' and ''S. acidolcaldarius''. They are already known for the role they play in post-transcriptional modifications and removal of introns from ribosomal RNA in Eukaryote.

The genome of ''Sulfolobus'' is characterized by the presence of short tandem repeats, insertion and repetitive elements. It has a wide range of diversity with 200 different insertion sequence elements.

Thermophilic reverse gyrase

The stabilization of the DNA's structure against denaturation, in the Archaea, is due to the presence of a particular thermophilic enzyme, reverse gyrase. It was discovered in hyper-thermophilic and thermophilic Archaea and Bacteria. There are two genes in ''Sulfolobus'' that each encode a reverse gyrase. It is defined as an atypical DNA topoisomerase and the basic activity consists of the production of positive supercoils in a closed circular DNA. Positive supercoiling is important to prevent the formation of open complexes. Reverse gyrases are composed of two domains: the first one is the helicase and second one is the topoisomerase I. A possible role of reverse gyrase could be the use of positive supercoiling to assemble chromatin-like structures. In 1997, scientists discovered another important feature of ''Sulfolobus'': a type-II topoisomerase, called TopoVI, whose A subunit is homologous to the meiotic recombination factor, Spo11, which plays a predominant role in the initiation of meiotic recombination in all Eukaryotes.

''S. solfataricus'' is composed of three topoisomerases of type I, TopA and two reverse gyrases, TopR1 and TopR2, and one topoisomerase of type II, TopoVI.

DNA binding proteins

In the phylum Thermoproteota, there are three proteins that bind to the minor groove of DNA-like histones, Alba, Cren7, and Sso7d, that are modified after the translation process. These histones are small and have been found in several strains of ''Sulfolobus,'' but not in other genomes. Chromatin protein in ''Sulfolobus'' represent 1-5% of the total genome; they can have both structural and regulatory functions and look like human HMG-box proteins because of their influence on genomes, expression, stability, and epigenetic processes. In species lacking histones, they can be acetylated and methylated like eukaryotic histones. ''Sulfolobus'' strains present different peculiar DNA binding proteins, such as the Sso7d protein family. They stabilize the DNA's structure, preventing denaturation at high temperature and thus promoting annealing above the melting point.

The major component of Archaea chromatin is represented by Sac10b family protein known as Alba (acetylation lowers binding affinity). These proteins are small, basic, and dimeric nucleic acid-binding proteins. Furthermore, it is conserved in most sequenced Archaea genomes. The acetylation state of Alba affects promoter access and transcription in vitro, whereas the methylation state of another ''Sulfolobus'' chromatin protein, Sso7D, is altered by culture temperature.

The work of Wolfram Zillig's group, which represented early evidence of the eukaryotic characteristics of transcription in Archaea has since made ''Sulfolobus'' an ideal model system for transcription studies. Recent studies in ''Sulfolobus'' in addition to other Archaea species, mainly focus on the composition, function, and regulation of the transcription machinery, and on fundamental conserved aspects of this process in both Eukaryotes and Archaea.

DNA transfer

Exposure of ''Saccharolobus solfataricus'' to DNA damaging agents, such as ultraviolet ( UV) irradiation, bleomycin, or mitomycin C, induces cellular aggregation. Other physical stressors like changes in pH or temperature, do not induce aggregation, suggesting that the 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-induced 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.

Metabolism

''Sulfolobus solfataricus'' is known to grow by chemoorganotrophy with the presence of oxygen while on a variety of organic compounds such as sugars, alcohols, amino acids, and aromatic compounds like phenol.

It uses a modified Entner-Doudroff pathway for glucose oxidation and the resulting pyruvate molecules can be totally mineralized in a TCA cycle.

Molecular oxygen is the only known electron acceptor at the end of the electron transport chain. Other than organic molecules, this Archaea species can also utilize hydrogen sulfide and elementary sulfur as electron donors and fix , possibly by means of the HP/HB cycle, making it also capable of living by chemoautotrophy. Recent studies have also found the capability to grow, albeit slowly, by oxidizing molecular hydrogen.

''Ferredoxin''

Ferredoxin is suspected to act as the major metabolic electron carrier in ''S. solfataricus''. This contrasts with most species within the Bacteria and Eukaryote groups of organisms, which generally rely on nicotinamide adenine dinucleotide hydrogen ( 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 Thermoproteota and "Euryarchaeota".

Ecology

''Habitat''

''S. solfataricus'' is an extreme thermophile from the Archaea family. ''S. solfataricus,'' and the members of the related genus ''Sulfolobus'' have optimal growth conditions in strong volcanic activity areas with high temperatures and very acidic pH. These specific conditions are typical of volcanic areas such as geyser or thermal springs. In fact, the most studied countries where these microorganisms were found are the U.S.A. (Yellowstone National Park), New Zealand, Iceland and Italy, notorious for volcanic phenomena. A study conducted by a team of Indonesian scientists has also shown the presence of a ''Sulfolobus'' community in West Java, confirming that high temperatures, low pH, and the presence of sulfur are necessary conditions for the growth of these microbes.

''Soil acidification''

''S. solfataricus'' is able to oxidize sulfur according to metabolic strategy. One of the products of these reactions is H+ and consequently, it will slowly acidify the surrounding area. Soil acidification increases in places where there are emissions of pollutants from industrial activity. This process reduces the number of heterotrophic bacteria involved in decomposition, which are fundamental for the process of recycling organic matter and ultimately slows the fertilization of soil.

Biotechnology: Untapping the resource ''Sulfolobus''

There is interest in using ''S. sulfataricus'' as a source of thermal stability enzymes for research and diagnostics as well as industries such as food, textile, cleaning, and the pulp and paper industry. Furthermore, this enzyme is overloaded due to its catalytic diversity, high pH, and temperature stability, increased to resistance organic solvents and resistance to proteolysis.

At present, tetra ester lipids, membrane vesicles with antimicrobial properties, trehalose components, and new β-galactooligosaccharides are becoming increasingly important.

β-galactosidase

The thermostable enzyme β-galactosidase was isolated from the extreme thermophile archaebacterial ''S. solfataricus, strain MT-4.''

This enzyme is utilized in many industrial processes of lactose containing fluids by purifying and characterizing their physicochemical properties.

Proteases

The industry are interested in stable proteases as well as in many different ''Sulfolobus'' proteases that have been studied.

An active aminopeptidase associated with the chaperonin of ''S. solfataricus'' MT4 was described''.''

Sommaruga et al. (2014) also improved the stability and reaction yield of a well-characterized carboxypeptidase from ''S. solfataricus'' MT4 by magnetic nanoparticles immobilizing the enzyme.

Esterases/Lipases

A new thermostable extracellular lipolytic enzyme serine arylesterase was originally discovered for their large action in the hydrolysis of organophosphates from the thermoacidophilic archaeon ''S. solfataricus P1''.

Chaperonins

In reaction to temperature shock (50.4 °C) in E. coli cells, a tiny warm stun protein (S.so-HSP20) from ''S.solfataricus'' P2 has been effectively used to improve tolerance to temperature.

Since chaperonin Ssocpn (920 kDa), which includes adenosine triphosphate ( ATP), K+, and Mg² +, has not produced any additional proteins in ''S. solfataricus'' to supply collapsed and dynamic proteins from denatured materials, it was stored on an ultrafiltration cell, while the renatured substrates were moving through the film.

Liposomes

Because of its tetraether lipid material, the membrane of extreme thermophilic Archaea is unique in its composition. Archaea lipids are a promising source of liposomes with exceptional stability of temperature, pH, and tightness against the leakage of solute. Such archaeosomes are possible instruments for the delivery of medicines, vaccines, and genes.

See also

* List of Archaea genera

References

Further reading

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External links

Type strain of ''Sulfolobus solfataricus'' at Bac''Dive'' - the Bacterial Diversity Metadatabase

{{Taxonbar, from=Q3503466

Thermoproteota
Archaea described in 1980