User:Inquiringmindhive/Strain 121

Strain 121 (Geogemma barossii) is a single-celled microbe of the domain Archaea. It was first discovered 320 km (200 mi) off Puget Sound, in a deep sea hydrothermal vent along the Endeavour segment of the Juan de Fuca Ridge. Strain 121 is a hyperthermophile able to reproduce at 121 C, hence its name. It was (at the time of its discovery) the only known form of life that could tolerate such high temperatures. A temperature of 130 C is biostatic for Strain 121, meaning that although growth is halted, the archaeon remains viable, and can resume reproducing once it has been transferred to a cooler medium.

The ability to grow at 121 C is significant because medical equipment is exposed to this temperature for sterilization in an autoclave. Prior to the 2003 discovery of Strain 121, a fifteen-minute exposure to autoclave temperatures was believed to kill all living organisms. However, Strain 121 is not infectious in humans, because it cannot grow at temperatures near 37 C.

Strain 121 metabolizes by reducing iron oxide. It is able to do this by using H2 as an electron donor.

During respiration, Strain 121 will utilize Fe(III) as an external electron acceptor. Geochemical evidence has shown the significance of Fe(III) as an electron acceptor for microbes on early Earth. In addition to this, microbiological evidence presents the possibility that Fe(III) reduction was one of the first forms of microbial respiration.

Characteristics
Strain 121 has a coccoid shape and is characterized by lophotrichous flagella.

Cell Structure
Strain 121 has a structure that is consistent among many Archaea. It contains a cell envelope with three major components: a cell wall, a cytoplasmic membrane and a periplasmic space.

Genome Structure
Geogemma barossii has a single circular chromosome. Although this feature is common among the archaeal domain, some archaea can contain more than one chromosome. Upon examination of its 16S rDNA sequence, it was found that G. barossii is closely related to Pyrodictium occultum and Pyrobaculum aerophilum.

Metabolism
Geogemma barossii metabolizes by reducing Fe3+ to Fe2+, a more soluble form of iron. It reduces Fe3+ by using H2, an inorganic electron donor. Through this solubilization process, magnetite is formed.

Respiration
Microbiological evidence, along with geochemical evidence, has indicated the possibility that Fe(III) solubilization was the first form of microbial respiration. Prior to this, it was thought that sulphur reduction was one of the first forms of microbial respiration. Through geochemical evidence, the significance of Fe(III) as an electron acceptor on early Earth was characterized. This evidence was further supported by a test conducted on Thermotoga maritima. Thermotoga maritima is a hyperthermophilic microorganism known for its ability to produce hydrogen gas through fermentation. Upon the addition of Fe(III), it was found that this organism could grow using an external electron acceptor. The abundance of Fe(III) on early Earth, along with the the use of Fe(III) by Thermotoga maritima, indicate the role of Fe(III) solubilization on early Earth. In addition to this, it was found that Archaea and Bacteria most closely related to the last common ancestor of modern life can perform Fe(III) solubilization.