Crenarchaeota

Crenarchaeota are an abundant mesophilic archaea. The name comes from two greek words "fountain" and ancient". Crenarchaeota are based on molecular sequences that are compared and seem similar to one another. Crenarchaeota are prokaryotic - like all Archaea. Instead of fatty acids, they are bound by lipid membranes that contain isoprinoid side chains. The cocci size of a Crenarchaeota range from <1 um in diameter to 100 um in length.

Crenarchaeota come in a range of cell shapes, they include: cocci, lobed cells, discs, thin filaments and rods. This type of archaea is motile and possess flagella in order to do so. Crenarchaeota re very diverse, they can be facultative anaerobes, aerobes, or even anaerobes. They usually use use sulfur in some way for and utilize it for energy metabolism. Many of the species are primary producers of organic matter - which use carbon dioxide as a carbon source. They gain energy by the reduction of sulfur or nitrate and oxidation of inorganic substances like sulfur and hydrogen. Other kinds species grow by fermentation or even aerobic or anaerobic respiration. 

Something very unique about Crenarchaeota is their tolerance for extreme environments of acidity and high temperature. Many organisms prefer to be in a neutral environment to slightly acidic  pH ranges. Crenarchaeota flourish at pH 1-2 and die above pH of 7! Their optimum growth temperatures range from 75° to 105°C. Some even go up to 113°C! Other common habitats include very cold habitats and highly saline, acidic, or alkaline water. However, archaea also include mesophiles that grow in mild conditions, in marshland, sewage, the oceans, and soils.

Examples of Crenarchaeotans include:

Desulfurococcales: irregular coccoid/disc-shaped, hyperthermophiles, and found in submarine hydrothermal systems and hot springs. 

Sulfolobales: aerobic and faculatative anaerobes, chemolithotrophic cocci (extreme thermoacidophiles). They lack their peptidoglycan in their cell walls. 

Thermoproteales: rod or disc shaped. They are anaerobic thermophiles and found in hot water, mud holes, and superheated submarine environments. 

References: 

Barns, S., & Burggraf, S. (2004). Crenarchaeota. Retrieved May 5, 2014, from 
     Tree of Life Project website: http://tolweb.org/Crenarchaeota

Habitats and Energy Metabolism of Crenarchaeota. (n.d.). Retrieved 2014, from 
     Boundless website: https://www.boundless.com/microbiology/ 
     microbial-evolution-and-phylogeny/crenarchaeota/ 
     habitats-and-energy-metabolism-of-crenarchaeota/ 

Lots of Crenarchaeota and some confusing N cycling in a really hot, really acidic CA lake. http://t.co/7BIKBoRXJZ
— Julian Damashek (@scientificjules) June 19, 2013

今飼っている Crenarchaeota の Sulfolobus tokodaii 、その名の通り東工大の先生が発見された生物だから、今日から親しみを込めて「テックちゃん」と呼ぼう。
— 団長@精神豊饒化活動 (@K_dancho1116) May 29, 2013

Crenarchaeota are highly prevalent on earth... you'll find them even in the pond in your garden. #SMBE12
— Marnix Medema (@marnixmedema) June 24, 2012

Identification of missing genes and enzymes for autotrophic carbon fixation in crenarchaeota. http://t.co/jmkfRyKW
— Mas Kot (@maskot1977) October 5, 2011

#IEG Puri Lopez-Garcia Marine planktonic archaea = Crenarchaeota, Euryarchaeota, Group I, Group 1A, & II/III. Group I = Thaumarchaeota.
— Francis Martin (@fmartin1954) October 17, 2011

Cuba try baca. - Korarchaeota - Euryachaeota - Crenarchaeota - Nanoarchaeota - Sulfolobus accidocaldarius Klau lah nama org mcm ni. Haihh
— 6/\6 (@ninie_193) December 15, 2013