Species: S. metallicus 
Figure 13: Sulfolobus Metallicus SEM
Why does the organism belong in this domain?
The Domain Archaea only contains organisms that are prokaryote, unicellular and reproduce only asexually. Also, the organism mode of nutrition includes lithotrophs, which take their energy from inorganic substances, phototrophs, energy source that is the sun, and organotrophs, whom use organic energy to obtain its energy.  This organism is a prokaryotic cell, which is unicellular.  Since Sulfolobus Metallicus is prokaryote, the cell has to reproduce only asexually and is unable to produce sexually. Sulfolobus Metallicus is hyperthermophilic and chemolithoautotrophic only thriving in high temperatures and uses energy from mineral sources, receiving its energy from elemental sulfur.  Sulfur is an inorganic substance, which provides the energy to the organism. This metabolism, as a whole category, is known as the lithotrophs. These characteristics represent an Archaea organism, however it is also characteristics of a Bacteria organism. A main difference between these two Domains is that the Archaea functions and grows only in harsh, severe environment. These type of organisms are called extremophiles, which no bacteria organism is.  The Sulfolobus Metallicus functions under high temperature, growing in stress conditions like areas where high concentration of metals could be found, and is considered an extremophile.  They also contain methanogens, which belong in the archaea category because of the high temperature it can endure. 
Sulfolobus Metallicus have the ability to oxidize sulfur, and their GC-content sit useful to this organism. The organism obtains its energy is by absorbing sulfur compounds then using them for the organism’s energy source.  18 out of 30 of the regulating proteins that are in the organism, are found to help in the production and conversion of the energy. That is 60% of the proteins the organism contains.  This type of metabolism, where the energy source for the organism is inorganic compounds, like sulfur, are referred to as hyperthermophilics and chemolithoautotrophics. Sulfolobus Metallicus grow in the temperature of around 50- 75 C° which is 122-167 F°. This environment is mostly impossible for a human to live in.  Sulfolobus Metallicus, can also live in a high concentration of heavy metals. One of the heavy metals that this organism has tolerance for is the metal copper.  This just demonstrates the extreme conditions it can live in, making the organism an extremophile. The pH of this organism is found at 1 and at 4.5. The concentration of sodium chloride, Sulfolobus Metallicus can handle is up to 3%.  The location where Sulfolobus Metallicus can be found is the volcanic springs, which is an environment that is considered extreme.  When a biotrickling filter is used with the help of Sulfolobus Metallicus, the maximum of removal capacity increased from 40g S/m3h to 70g S/m3h. Therefore, this organism is used in biofiltration to help remove waste gas at high temperatures that are exposed to H2S.  Sulfolobus Metallicus is able to oxidize H2S at high temperature. This is the major function that allows for this organism to support the biotrickling filter for the removal capacity of H2S. 
Figure 5: Sulfolobus metallicus, Light Microscope
Figure 6: Sulfolobus metallicus close up
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