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Astrobiology: cyanobacteria from desert to space
D. Billi in collaboration with E. I. Friedmann (NASA Ames Research Center, Space Science Division,
CA, USA), C. Cockell (Planetary and Space Sciences Research Institute, Open University, Milton,
UK), S. Onori (Università della Tuscia, Viterbo, Italy).
Organisms thriving on Earth under extreme conditions suggest that live could exist under similar
conditions in other planets. Cyanobacteria such as Chroococcidiopsis, from extremely hot and cold
deserts, provide unique models to gain an insight on the limits of life on Earth and search extinct or
extant life on other planets. In the McMurdo Dry Valleys, Antarctica, Chroococcidiopsis finds refuge
in porous rocks and thus escapes the outside hostile climate, that makes this environment the closest
terrestrial analogue of Mars. The capability of desert Chroococcidiopsis to survive extreme desiccation
(anhydrobiosis) and high doses of both ionizing (up to 15 KGy ) and ultraviolet (simulated Martian
UV flux) radiation, makes it an appropriate model-test in astrobiology.
Cryptoendolithic growth of Chroococcidiopsis in a lichen-dominated microbial community, Ross
Desert (McMurdo Dry Valleys, Antarctica), kindly provided by E. Imre Friedmann
1. Cockell CS, Schuerger AC, Billi D, Friedmann EI, Panitz C. 2005. Effects of a simulated
Martian UV flux on the cyanobacterium Chroococcidiopsis sp. 029. Astrobiol. 5:127-40.
2. Onofri S, Cockell C, Edwards H, Friedmann EI, Billi D, Zucconi L, Selbmann L, de Hoog S,
Sterflinger K, and Grady M. Lithobionts: Ecological niches for life in lithic habitats: models for
searching past life on Mars. 2003. Congress on exobiology -Mars: the search for life; focus
point: Terrestrial analogues. Madrid, 18-20 November, pp 84-85.
3. Billi D, Friedmann EI, Hofer KG, Grilli Caiola M, Ocampo-Friedmann R. 2000. Ionizingradiation resistance in the desiccation-tolerant cyanobacterium Chroococcidiopsis. Appl.
Environm. Microbiol. 66: 1489-1492.
Desiccation tolerance in cyanobacteria
Researches take advantage of the fact that Daniela Billi is entrusted of maintaining 250 isolates of
Chroococcidiopsis, and related genera, belonging to the Culture Collection of Microorganisms from
Extreme Environments (CCMEE) established by E.Imre Friedmann (Florida State University,
Thallahassee, FL).
Cyanobacteria of the genus Chroococcidiopsis from extremely dry hot and cold deserts leave at
absolute limit for life, being able to avoid and /or repair damages induced by desiccation. The
complete removal of water from cells, storage in the dried state and rewetting, impose physiological
constraints which are lethal to the majority of the organisms. Desiccation induced damages span from
those mediated by free radicals, reactive oxygen species, Maillard and Fenton reactions, to those
caused by the phase transitions of phospholipid bilayers. Researches aim to highlight the cellular and
molecular mechanisms employed by desert strains of Chroococcidiopsis to repair DNA induced
damages and face oxidative stress. Researches take advantage of molecular biology tools developed
for this cyanobacterium, such as gene transfer methods and gene reporter systems. To date desert
strains of Chroococcidiopsis represent the only desiccation tolerant cyanobacteria suitable to genetic
manipulation.
Colonies of Chroococcidiopsis sp.
expressing luxAB.
1. Billi D, Potts M. 2002. Life and death of dried prokaryotes. Research in Microbiology 153:712.
2. Billi D, Friedmann EI, Helm RF, Potts M. 2001. Gene transfer to the desiccation-tolerant
cyanobacterium Chroococcidiopsis. J. Bacteriology 183: 2298-2305.
3. Billi D., Potts M. 2000. Life without water: responses of prokaryotes to desiccation, p 181192. In K.B. Storey and J.M. Storey (eds), Environmental stressors and gene responses, Vol.
1 Cell and Molecular response to stress , Elsevier Science, New York..
4. Billi D., Wright D. J., Helm R. F., Prickett T., Potts M. Crowe J. H. 2000. Engineering
desiccation tolerance in Escherichia coli. Applied and Environmental Microbiology.
66:1680-1684.
5. Billi D, Grilli Caiola M., Paolozzi L., Ghelardini P. 1998. A method for DNA extraction
from the desert cyanobacterium Chroococcidiopsis and its application to identification of
ftsZ. Applied and Environmental Microbiology 64: 4053-4056.