strain 121

{{Short description|Species of archaeon}}

{{More footnotes|date=September 2024}}

{{Taxobox

| image =

| image_caption =

| domain = Archaea

| phylum = Thermoproteota

| classis = Thermoprotei

| ordo = Desulfurococcales

| familia = Pyrodictiaceae

| genus = Geogemma

| species = Geogemma barossii

}}

Strain 121 (Geogemma barossii) is a single-celled microbe of the domain Archaea. First discovered within a hydrothermal vent in the Northeast Pacific Ocean near the Endeavor segment of the Juan de Fuca Ridge, Strain 121 is a hyperthermophile capable of reproducing at {{convert|121|C|F}}, hence its name.{{Cite journal |last=Kashefi |first=Kazem |last2=Lovley |first2=Derek R. |date=August 15, 2003 |title=Extending the Upper Temperature Limit for Life |url=https://www.science.org/doi/10.1126/science.1086823 |journal=Science |language=en |volume=301 |issue=5635 |pages=934–934 |doi=10.1126/science.1086823 |issn=0036-8075|url-access=subscription }}{{Cite journal |last=Clarke |first=Andrew |date=April 2004 |title=The thermal limits to life on Earth |url=https://www.cambridge.org/core/product/identifier/S1473550413000438/type/journal_article |journal=International Journal of Astrobiology |language=en |volume=13 |issue=2 |pages=141–154 |doi=10.1017/S1473550413000438 |issn=1473-5504|doi-access=free }} Strain 121 is biostatic at {{convert|130|C|F}}, so while the archaeon is unable to reproduce until it has been transferred to a cooler medium, it remains viable at temperatures up to {{convert|131|C|F}}. Strain 121 possess a coccoid shape with lophotrichous flagellation, reaching approximately 1.0 μm in diameter. Strain 121 metabolizes by reducing iron oxide (Fe(III)), a molecule that is abundant within the sediment in hydrothermal vents.

The maximum growth temperature of strain 121 is 8 °C higher than the previous record holder, Pyrolobus fumarii (T_max = 113 °C).{{Cite journal |last=Cowan |first=D.A |date=February 2004 |title=The upper temperature for life – where do we draw the line? |url=https://linkinghub.elsevier.com/retrieve/pii/S0966842X03003160 |journal=Trends in Microbiology |language=en |volume=12 |issue=2 |pages=58–60 |doi=10.1016/j.tim.2003.12.002|url-access=subscription }} At the time of its discovery, Strain 121 was the only known form of life that could tolerate such high temperatures, but in 2008 Methanopyrus kandleri was discovered to be able to reproduce at temperatures as high as 122 °C. Autoclaves, which are an important tool in sterilization, operate at temperatures of {{convert|121|C|F}}, marking Strain 121 a particularly notable discovery. Prior to the 2003 discovery of Strain 121, a fifteen-minute exposure to autoclave temperatures was believed to kill all living organisms. However, as Strain 121 is unable to reproduce at temperatures below {{convert|85|C|F}}, it cannot infect humans, who have an average body temperature of approximately {{convert|37|C|F}}.{{Cite web |title=What Is a Normal Body Temperature? |url=https://health.clevelandclinic.org/body-temperature-what-is-and-isnt-normal |access-date=2024-11-21 |website=Cleveland Clinic |language=en}}

It appears highly improbable that Strain 121 marks the upper limit of viable growth temperature. It may very well be the case that the true upper limit lies somewhere in the vicinity of {{convert|140|to|150|C|F}}, the temperature range where molecular repair and resynthesis becomes unsustainable.