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Scientific classification Edit this classification
Domain: Bacteria
Phylum: Cyanobacteria
Class: Cyanophyceae
Order: Chroococcidiopsidales
Komárek et al. 2014[1]
Family: Chroococcidiopsidaceae
Komárek et al. 2014[1]
Genus: Chroococcidiopsis
Geitler, 1933
Type species
Chroococcopsis gigantea
Geitler, 1933
Chroococcidiopsis thermalis can photsynthesize in far-red light, and might be suitable for future Mars colonists.[2]

Chroococcidiopsis is a photosynthetic, coccoidal bacterium, and the only genus in the order Chroococcidiopsidales and in the family Chroococcidiopsidaceae. A diversity of species and cultures exist within the genus,[3] with a diversity of phenotypes. Some extremophile members of Chroococcidiopsis are known for their ability to survive harsh environmental conditions, including both high and low temperatures, ionizing radiation, and high salinity.

Desiccation resistance[edit]

The ability of Chroococcidiopsis to resist desiccation in arid environments is due in part because it colonizes the underside of translucent rocks. The underside of these rocks provides enough condensed moisture for growth while the rock's translucent nature allows just enough light to reach the organism for photosynthesis to occur.

Mars colonization[edit]

Due to its resistance to harsh environmental conditions, especially low temperature, low moisture, and radiation tolerance, Chroococcidiopsis has been thought of as an organism capable of living on Mars. Scientists have speculated about the possibility of introducing Chroococcidiopsis to the Martian environment to aid in the formation of an aerobic environment. In addition to oxygen production, Chroococcidiopsis could aid in the formation of soil on the Martian surface. On Earth, soil is formed by plant, microbial, and geophysical activity on a mineral substrate. The soil produced by chemical weathering of rocks and oxygen produced by photosynthesis could one day provide the conditions necessary for humans to grow food on Mars, possibly allowing for permanent human civilizations on the planet.[4][5] On a shorter time scale, cyanobacteria such as Chroococcidiopsis could be used in closed systems to produce resources for human-occupied outposts on Mars without altering the planet's surface or atmosphere.[6]

A space mission called EXPOSE-R2 was launched on 24 July 2014 aboard the Russian Progress M-24M,[7] and was attached on 18 August 2014 outside the ISS on the Russian module Zvezda.[8] The experiment included samples of Chroococcidiopsis that were exposed to simulated Martian atmosphere, UVC radiation and temperature extremes.[9] In 2022, the findings of the experiments were published.[10]

UV and desiccation resistance[edit]

Biofilms of Chroococcidiopsis were exposed to Mars-like UV-flux and desiccation for up to seven years.[11] Biofilms that were either (1) dried or (2) both dried and UV irradiated were able to recover. When these biofilms were rewetted the nucleotide excision repair genes encoding UvrA, UvrB and UvrC were over-expressed. This suggests that nucleotide excision repair of accumulated DNA damages contributed to the recovery.[citation needed]

See also[edit]


  1. ^ a b Komárek J, Kaštovský J, Mareš J, Johansen JR (2014). "Taxonomic classification of cyanoprokaryotes (cyanobacterial genera) 2014, using a polyphasic approach" (PDF). Preslia. 86: 295–335.
  2. ^ Weird Low-Light Bacteria Could Potentially Thrive on Mars,, accessed 6/18/2018
  3. ^ Cumbers J, Rothschild LJ (June 2014). "Salt tolerance and polyphyly in the cyanobacterium Chroococcidiopsis (Pleurocapsales)". Journal of Phycology. 50 (3): 472–482. doi:10.1111/jpy.12169. PMID 26988320. S2CID 23871779.
  4. ^ "Greening of the Red Planet". NASA. Archived from the original on 2011-03-18. Retrieved 2011-03-14.
  5. ^ Billi D, Friedmann EI, Hofer KG, Caiola MG, Ocampo-Friedmann R (April 2000). "Ionizing-radiation resistance in the desiccation-tolerant cyanobacterium Chroococcidiopsis". Applied and Environmental Microbiology. 66 (4): 1489–1492. Bibcode:2000ApEnM..66.1489B. doi:10.1128/aem.66.4.1489-1492.2000. PMC 92012. PMID 10742231.
  6. ^ Verseux C, Baqué M, Lehto K, de Vera JP, Rothschild LJ, Billi D (2015-08-01). "Sustainable life support on Mars – the potential roles of cyanobacteria". International Journal of Astrobiology. 15 (1): 65–92. Bibcode:2016IJAsB..15...65V. doi:10.1017/S147355041500021X. ISSN 1475-3006.
  7. ^ Gronstal AL (31 July 2014). "Exploring Mars in low Earth orbit". NASA's Astrobiology Magazine. Retrieved 2014-08-02.
  8. ^ Kramer M (18 August 2014). "Russian Cosmonaut Tosses Satellite for Peru During Spacewalk". Retrieved 2014-08-19.
  9. ^ Baqué M, de Vera JP, Rettberg P, Billi D (20 August 2013). "The BOSS and BIOMEX space experiments on the EXPOSE-R2 mission: Endurance of the desert cyanobacterium Chroococcidiopsis under simulated space vacuum, Martian atmosphere, UVC radiation and temperature extremes". Acta Astronautica. 91: 180–186. Bibcode:2013AcAau..91..180B. doi:10.1016/j.actaastro.2013.05.015. ISSN 0094-5765. Retrieved 14 January 2014.
  10. ^ Napoli A, Micheletti D, Pindo M, Larger S, Cestaro A, de Vera JP, Billi D (May 2022). "Absence of increased genomic variants in the cyanobacterium Chroococcidiopsis exposed to Mars-like conditions outside the space station". Scientific Reports. 12 (1): 8437. Bibcode:2022NatSR..12.8437N. doi:10.1038/s41598-022-12631-5. PMC 9120168. PMID 35589950.
  11. ^ Mosca C, Rothschild LJ, Napoli A, Ferré F, Pietrosanto M, Fagliarone C, et al. (2019). "Over-Expression of UV-Damage DNA Repair Genes and Ribonucleic Acid Persistence Contribute to the Resilience of Dried Biofilms of the Desert Cyanobacetrium Chroococcidiopsis Exposed to Mars-Like UV Flux and Long-Term Desiccation". Frontiers in Microbiology. 10: 2312. doi:10.3389/fmicb.2019.02312. PMC 6798154. PMID 31681194.

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