Bacteria; Cyanobacteria; Cyanophyceae; Chroococcales; Xenococcaceae NCBI link to find]
Chroococcidiopsis thermalis, Chroococcidiopsis gigantea, Chroococcidiopsis cubana, Chroococcidiopsis codiicola
Description and Significance
Chroococcidiopsis is a primitive, unicellular cyanobacteria. It can survive in a diverse array of harsh conditions. Chroococcidiopsis populations can survive under extreme temperatures or pHs, high levels of radiation, high concentrations of salt, and arid environments . It has been found in many extremely arid habitats, nitrate caves, airspace of porous rocks from Antarctic valleys, and hyper saline environments . It is an important microorganism to study due to its ability to survive in these extreme conditions. They release neurotoxins as a byproduct of their metabolism that can contaminated drinking water.
Chroococcidiopsis thermails genome is one chromosome that contains 6.69 megabase pairs (Mbp) made up of 6,033 genes and containing 5,752 encoding proteins . The genome has a G+C makeup of 44.4%.  Chroococcidiopsis was traditionally assigned under the order Pleurocapsales due to baeocyte formation, but only after phylogenetic studies on 16S rRNA sequence found that their closest living relative is the heterocyst differentiating cyanobacteria . "Chroococcidiopsis forms unique survival cells under nitrogen limiting conditions, and the sister group relationship with the heterocytous cyanobacteria shown here suggests that differentiation of these cells and heterocysts may be related processes (5). Chroococcidiopsis sp. TS-821 differ from other cyanobacteria by forming tetrameric or dimeric Photosystem I reaction centers rather than the usual trimmeric complexes most cyanobacteria have . Analyses comparing Chroococcidiopsis PsaL protein sequences to heterocyst-differientiating cyanobacteria reiterated their close relationship since heterocyst-differentiating cyanobacteria also form tetrameric centers of PSI .
Cell Structure, Metabolism and Life Cycle
Chroococcidiopsis is a negative Gram, spherical cyanobacteria. It is prokaryotic, meaning it lacks a nucleus. Chroococcidiopsis performs oxygenic photosynthesis. It produces ammonia, nitrites, or nitrates through nitrogen fixation. Heterocysts are commonly formed in low concentrations of nitrogen. The average cell has a diameter of 2-6 μm and is surrounded by thin, colorless, extracellular polysaccharide sheathes.They have a high desiccation tolerance due to the EPS that surround them. They are rarely found solitary, usually living in less spherical colonies, but occasionally the cells are gathered in free-living agglomerations. Cell division occurs in two possible ways. The first being successive binary division in different planes or by irregular cell division by multiple fissions (Geitler). Thylakoid distributions are irregular throughout the cell.
Ecology and Pathogenesis
Due to its primitive nature, it is thought that Chroococcidiopsis was a major contributor to transforming our early atmosphere by releasing oxygen as a byproduct that accumulated, creating an oxidizing environment. Another implication of Chroococcidiopsis is its ability to produce neurotoxic byproducts such as β-N-methylamino-L-alanine that can create a health hazard for drinking water. Consumption of the neurotoxin may lead to malfunctioning of the nervous system and in severe cases death. Chroococcidiopsis is currently thought to be one of the only microbes that would be capable of surviving in Mars' extreme environmental conditions. The possibility of farming Chroococcidiopsis to produce organic material to create soil and add oxygen to its atmosphere may one day be able to create conditions suitable for farming and life on Mars.
 Meng, L., Semchonok, D., Boekema. ““Characterization and Evolution of Tetrameric Photosystem I from the Thermophilic Cyanobacterium Chroococcidiopsis sp TS-821”. “The Plant Cell”. March 2014.]
 Billi, D., Friedmann, E., Helm, R., Potts, M. “”Gene Transfer to the Desiccation-Tolerant Cyanobacterium Chroococcidiopsis”. “Journal of Bacteriology”. 2001. Volume 183. p. 2298-2305.]
 NASA. “Greening of the Red Planet”. “National Aeronautics and Space Administration.” January 2001.]
 Geitler, L. “Chroococcopsis.”]
 Magana-Arachchi, M. Wanigatunge, R.P. “First report of genus Chroococcidiopsis (cyanobacteria) from Sri Lanka: a potential threat to human health”. Journal of the National Science Foundation”. 2013. Volume 41. P. 65-68.]
 ”Chroococcidiopsis thermalis.”]
 Fewer, D., Friedl, T., Budel, B. "Chroococcidiopsis and heterocyst-differentiating cyanobacteria are each other's closest living relatives". Molecular Phylogenetic Evolution." 2002. Volume 23. p. 82-90.]
Page authored by Lauren Pifer, student of Prof. Jay Lennon at IndianaUniversity.