Endolithic Life In Hot Deserts

Cryptoendolithic algae from hot, semiarid lands and deserts were first described from the Negev Desert (Friedmann et al., 1967). Cryptoendoliths of hot desert were then documented in North America (Friedmann, 1972; Bell et al., 1983, 1986) and South Africa (Critchley et al., 1987). The most common substrate are porous, crystalline sandstone and, less often, limestone. The first report of hot desert cryptoendoliths identified the coccoid cyanobacteria Chroococcidiopsis and Gleocapsa (Friedmann, 1971, 1980). Bell et al. (1986) and Critchley et al. (1987) revealed a rich flora including chlorophytes. Green algae are usually represented by coccoids or sarcinoids, in which Coccomyxa, Fasiculochloris and Friedmannia prevail. Tests on the effect of water stress in Chrooccoccidiopsis and Chroococcus cells isolated from rocks revealed that Chroococcidiopsis strains were not particularly resistant to low water potential, whereas desiccated cells of Chroococcidiopsis restarted photosynthesis within five minutes after rewetting (Potts and Friedmann, 1981). The tolerance to desiccation showed by these microorganisms and their ability to quickly activate their metabolism in response to sufficient liquid water or vapor concentration enables survivorship in arid environments. The crypto-endolithic microhabitat may provide sufficient moisture for the survival of microorganisms. Most of the green algae react to rewetting with rapid production of a motile phase with consequent expansion of the colonized area (Bell, 1993). Friedmann and Galun (1974) pointed out that the increased thermal load of the rocks could probably lead to frequent dew formation on the rock surface. This water may be taken via capillary action. Water may not stay in liquid state, but once inside the rock matrix, it may be retained in the form of vapor and, in conjunction with the lack of convection within the rock, loss to the outside can be delayed. Desert lichens can use atmospheric vapor (>80% RH, relative humidity) as a water source (Lange, 1986). Generally, the ability to utilize water vapor varies widely for green algae and cyanobacteria (Lange et al., 1986). For example, cryptoen-dolithic cyanobacteria from the sandstones of the Negev Desert (Potts and Friedmann, 1981; Palmer and Friedmann, 1990) photosynthesize only at very high matric water potential (>6.9 Mpa, 90% RH, relative humidity, at 20°C).

The most crystalline sandstones contain calcium carbonate as a crystal cementing material and it is likely that endoliths solubilize this material. The solubilization of rock cementing materials, freezing and thawing, and possibly pressure exerted by algal growth within the rock air spaces may contribute to exfoliation of rock (Friedmann and Ocampo-Friedmann, 1984; Bell et al., 1986). Once exposed, the algae probably dry and blow away. In case of available liquid water before they die under surface conditions, they might be drawn into the rock matrix.

Sulfate minerals in the form of gypsum crusts can be common in arid environments, such as salt lakes. Translucent gypsum crusts can host endolithic communities (Fig. 3) and retain microbial signatures (Oren et al., 1995; Douglas and Yang, 2002; Hughes and Lawley, 2003; Dong et al., 2007; Ionescu et al., 2007). Gypsum and other sulfates can provide microenvironments that protect these microorganisms from exposure to extreme temperature, UV flux, and desiccation, yet they are sufficiently translucent to allow the photosynthesis (Friedmann, 1982).

Figure 3. Environmental scanning electron (ESEM) micrograph of endolithic microorganisms in a gypsum crust along the border of the Chott el Jerid (Southern Tunisia). Endolithic bacterial cells embedded in extracellular polymeric substances (arrow). Scale bar: 10 cm.

The rapid sealing provided by the evaporite precipitation in arid and saline areas, such as continental and coastal sabkhas, seem to be a useful condition for testing the preservation potential of microbial signatures in the geological record (Barbieri et al., 2006). Because of their wide diffusion, evaporites can be ideal for the reconstruction of types of microbial signatures and their preservation over geological times. Evaporite minerals have also the advantage of preserving fluid inclusions that can retain information of the environment of mineral precipitation, as well as biotic remains. In inclusions from Permian halite cements sampled in the Salado Formation (New Mexico), for example, spores of the halotolerant bacterium Virgibacillus have been recovered (Vreeland et al., 2000; Satterfield et al., 2005).

3. Endoliths as Models for the Search of Martian Life

In environments characterized by harsh conditions, such as in hot and cold deserts, several studies have shown the survival of microorganisms in endolithic niches (Friedmann, 1967; Palmer and Friedmann, 1990; Potts and Friedmann, 1981 Nienow et al., 1988a,b; Vestal, 1988; Oren et al., 1995; Wierzchos and Ascaso, 2001, 2002; Hughes and Lawley, 2003; Onofri et al., 2004; Wierzchos et al, 2006; Dong et al., 2007; Pointing et al., 2007; Walker and Pace, 2007). Because the Antarctic Dry Valley and the Atacama Desert are considered the most hostile lithic environments for the microbial life on the Earth surface (Dose et al., 2001), the recovery of cryptoendolithic microorganisms in rocks from both these regions is a compelling example of survival of microorganisms in extremely dry conditions. These environments are therefore considered to be a good terrestrial analogue for Mars (McKay et al., 1992; Navarro-Gonzales et al., 2003). Cryptoendolithic mode life might occur in Mars environments when the Mars surface became progressively drier and colder (Friedmann and Koriem, 1989).

Recent data from the European Space Agency's Mars Express and NASA's Mars Exploration Rover missions have documented the presence of hydrated sulfate deposits on the surface of Mars (Squyres et al., 2004; Vaniman et al., 2004; Langevin et al., 2005) in environmental settings interpreted as analogues to terrestrial continental sabkhas (McLennan et al., 2005; Gendrin et al., 2005). Furthermore, halite has been identified in mineral assemblages of SNC meteorites arising from Mars (Gooding, 1992; Bridges and Grady, 2000; Sawyer et al., 2000; Treiman et al., 2000) suggesting that the evaporite rocks might be relatively common on Mars surface. This finding has sparked off considerable interest in the astrobiological potential of the evaporite salts (Krumbein et al., 2004; Barbieri et al., 2006; Wierzchos et al., 2006), which can be considered a good target for the investigation of terrestrial analogues of Martian environments. Evaporite mineral precipitation can provide protection from cosmic radiation and allow certain life forms, for example dormant bacterial spores, to survive in salt fluid inclusions for calculated time intervals of more than 100 million years in terrestrial and Martian conditions (Kminek et al., 2003). Inhabitants of hypersaline and arid environments include stress resistant microorganisms, such as the cyanobacterium Chroococcidiopsis, which has been proposed as pioneer microorganism for the terraforming of Mars (Friedmann and Ocampo-Friedmann, 1995).

The study of Earth's analogues of potential extraterrestrial environments is a prerequisite for astrobiology and planetary exploration. The settlement of how and where life survives in the most extreme terrestrial conditions, as well as the agents involved in its preservation processes and delivery to the fossil record, and lastly, the combined analytical techniques for its study and recognition, are all crucial in the development of strategies for future planetary missions in the search for life. In particular, the Mars Sample Return mission, based on an international collaboration between ESA, NASA, and other space agencies, is planning to bring Martian rock samples back to Earth in the next decade. For a success of this pioneering mission, which is also designed to answering the question of life on Mars, preparatory studies on terrestrial near-surface environments are required. In-depth analysis of the biota with endolithic mode of life, such as the ones that inhabit certain terrestrial extreme environments may help for finding the best techniques for their recognition. Because Martian near ground surfaces have the advantage of easy sample collection, microbial communities with endolithic strategies should have a special interest for astrobiology.

4. Acknowledgements

The authors would like to thank Maud Walsh and two anonymous reviewers for useful suggestions to improve this chapter.

5. References

Ascaso, C. and Wierzchos, J. (2002) New approaches to the study of Antarctic lithobiontic microorganisms and their inorganic traces, and their application in the detection of life in Martian rocks. Int. Microbiol. 5, 215-222. Ascaso, C. and Wierzchos, J. (2003) The search for biomarkers and microbial fossils in Antarctic rocks microhabitats. Geomicrobiol. J. 20, 439-450. Banerjee, M., Whitton, B.A. and Wynn Williams, D.D. (2000) Phosphatase activities of endolithic communities on rocks of the Antarctic Dry Valleys. Microb. Ecol. 39, 89-91. Barbieri, R., Stivaletta, N., Marinangeli, L. and Ori, G.G. (2006) Microbial signatures in sabkha evaporite deposits of Chott el Gharsa (Tunisia) and their astrobiological implications. Planet. Space Sci. 54, 726-736.

Bell, R.A. (1993) Cryptoendolithic algae of hot semie lands and deserts. J. Phycol. 29, 133-139. Bell, R.A., Athey, P.V. and Sommerfield, M.R. (1983) Preliminary observations on an endolithic alga of northwestern Arizona. J. Phycol. (Suppl.) 19, 7. Bell, R.A., Athey P.V. and Sommerfield, M.R. (1986) Cryptoendolithic algal communities of the

Colorado Plateau. J. Phycol. 22, 429-435. Bridges, J.C. and Grady, M.M. (2000) Evaporite mineral assemblages in the nakhlite (Martian) meteorites. Earth Planet. Sci. Lett. 176, 267-279.

Campbell, S.E. (1982) Precambrian endoliths discovered. Nature 299, 429-431.

Cockell, C.S. (2000) The ultraviolet history of the terrestrial planet-implications for biological evolution. Planet. Space Sci. 48, 203-214.

Connon, S.A., Lester, E.D., Shafaat, H.S., Obenhuber, D.C. and Ponce, A. (2007) Bacterial diversity in hyperarid Atacama Desert soils. J. Geophys. Res. 112, G04S17.

Cowan, D.A. and Ah Tow, L. (2004) Endangerd Antarctic environments. Annu. Rev. Microbiol. 58, 649-690.

Critchley, A.T., Wood, J., Horiguchi, T. and Bruton, A.G. (1987) An ultrastructural insight into a cryptoendolithic community. Proc. Electr. Microsc. Soc. S. Afr. 17, 101-102.

de la Torre, J.R., Goebel, B.M., Friedmann, E.I. and Pace, N.R. (2003) Microbial diversity of cryptoendolithic communities from Mc Murdo Dry Valleys, Antarctica. Appl. Environ. Microbiol. 69, 3858-3867.

de los Rios, A, Wierzchos, J., Sancho, L.G. and Ascaso, C. (2003) Acid microenvironments in microbial biofilms of Antarctic endolithic microecosystems. Environ. Microb. 5, 231-237.

de los Rios, A., Wierzchos, J., Sancho, L.G. and Ascaso, C. (2004) Exploring the physiological state of continental Antarctic endolithic microorganisms by microscopy. FEMS Microbiol. Ecol. 50, 143-152.

Dong, H., Rech, J.A., Jiang, H., Sun, H. and Buck, B.J. (2007) Endolithic cyanobacteria in soil gypsum: occurrences in Atacama (Chile), Mojave (United States), and Al-Jafr Basin (Jordan) Deserts. J. Geophys. Res. 112, G02030.

Dose, K., Bieger-Dose, A., Birgit, E., Feister, U., Gomez-Silva, B., Klein, A., Risi, S. and Stride, C. (2001) Survival of microorganisms under the extreme conditions of the Atacama Desert. Origins Life Evol. B., Springer Netherlands Publisher, 31, 287-303.

Douglas, S. and Yang, H. (2002) Microbial signatures in evaporites: presence of rosickyte in an endoevaporitic microbial community from Death Valley. California. Geology 30, 1075-1078.

Drees, K.P., Neilson, J.W., Betancourt, J.L., Quade, J., Henderson, D.A,. Pryor, B.M. and Maier, R.M. (2006) Bacterial Community Structure in the Hyperarid Core of the Atacama Desert, Chile. Appl. Environ. Microbiol. 72, 7902-7908.

Friedmann, E.I. (1971) Light and scanning electron microscopy of endolithic desert algal habitat. Phycologia 10, 411-428.

Friedmann, E.I. (1972) Ecology of lithophytic algal habitats in Middle Eastern and North America Desert. In: L.E. Rodin (ed.) Ecophysiological Foundation of Ecosystems Productivity in Arid Zone. U.S.S.R. Academy of Science, Nauka, Leningrad, pp 182-185.

Friedmann, E.I. (1980) Endolithic microbial life in hot and cold deserts. Origins Life 10, 223-235.

Friedmann, E.I. (1982) Endolithic microorganisms in the Antarctic cold desert. Science 215, 1045-1053.

Friedmann, E.I. and Galun, M. (1974) Desert algae, lichens, and fungi. In: G.W. Brown (ed.) Desert Biology, Vol II. Academic, New York, pp 165-203.

Friedmann, E.I. and Koriem, A.M. (1989) Life on Mars: how it disappeared (if it was ever there). Adv. Space Res. 9, 167-172.

Friedmann, E.I. and Ocampo, R. (1976) Endolithic blue-green algae in the dry Valley: primary producers in the Antarctic desert ecosystem. Science 193, 1247-1249.

Friedmann, E.I. and Ocampo-Friedmann, R. (1984) Endolithic microorganisms in extreme dry environments: analysis of lithobiontic microbial habitat. In: M.J. Klug and L.A. Reddy (eds.) Current Perspectivies in Microbial Ecology. American Society for Microbiology, Washington, DC, pp 177-185.

Friedmann, I.E. and Ocampo-Friedmann, R. (1995) A primitive cyanobacterium as pioneer microorganism for Terraforming Mars. Adv. Space Res. 15, 243-246.

Friedmann, E.I. and Weed, R. (1987) Microbial trace-fossil formation, biogenous, and abiotic weathering in the Antarctic cold desert. Science 236, 703-705.

Friedmann, E.I., Lipkin, Y. and Ocampo-Paus, R. (1967) Desert algae of the Negev (Israel). Phycologia 6, 185-200.

Friedmann, E.I., Mckay, C.P. and Niewon, J.A. (1987) The cryptoendolithic microbial environment in the Ross Desert of Antarctica: continuous nanoclimate data, 1984-1986. Polar Biol. 7, 273-287.

Friedmann, E.I., Hua, M. and Ocampo-Friedmann, R. (1988) Cryptoendolithic lichen and cyanobac-terial communities of the Ross Desert, Antarctica. Polarforschung 58, 251-259.

Gendrin, A., Mangold, N., Bibring, J.-P., Langevin, Y., Gondet, B., Poulet, F., Bonello, G., Quantin, C., Mustard, J., Arvidson, R. and LeMouelic, S. (2005) Sulfates in Martian layered terrains: the OMEGA/Mars Express view. Science 307, 1587-1591.

Gerdes, G., Krumbrein, W.E. and Noffke, N. (2000) Evaporite microbial sediment. In: R.E. Riding and S.M. Awramik (eds.) Microbial Sediments. Berlin/Heidelberg, Springer, pp 196-207.

Golubic, S., Friedmann, I. and Schneider, J. (1981) The lithobiontic ecological niche, with special reference to microorganisms. J. Sediment. Petrol. 51, 0475-0478.

Gooding, J.L. (1992) Soil mineralogy and chemistry on Mars: possible clues from salt and clays in SNC meteorites. Icarus 99, 28-41.

Grant, W.D., Gemmell, R.T. and Mcgenity, T.J. (1998) Halophiles. In: K. Horikoshi and W.D. Grant (eds.) Extremophiles: Microbial Life in Extreme Environments. Wiley Series in Ecological and Applied Microbiology, Wiley-Liss, New York, pp 93-132.

Hirsch, P., Hoffmann, B., Gallikowsky, C.C., Mevs, U., Siebert, J. and Sittig, M. (1988) Diversity and identification of heterotrophs from Antarctic rocks of the McMurdo Dry Valleys (Ross Desert). Polarforschung 58, 261-269.

Horowitz, N.H., Cameron, R.E. and Hubbard, J.S. (1972) Microbiology of the Dry Valleys of Antarctica. Antarctic. Sci. 176, 242-245.

Hughes, K.A. and Lawley, B. (2003) A novel Antarctic microbial endolithic community within gypsum crusts. Environ. Microbiol. 5, 555-565.

Ionescu, D., Lipski, A., Altendorf, K. and Oren, A. (2007) Characterization of the endoevaporitic microbial communities in a hypersaline gypsum crust by fatty acid analysis. Hydrobiologia 576, 15-26.

Kminek, G., Bada, J.L., Pogliano, K. and Ward, J.F. (2003) Radiation-dependent limit for the viability of bacterial spores in halite fluid inclusions and on Mars. Radiat. Res. 159, 722-729.

Knoll, A.H., Golubic, S., Grenn, J. and Sweet, K. (1986) Organically preserved microbial endoliths from the Late Proterozoic of East Greenland. Nature 321, 856-857.

Krumbein, W.E., Gorbushina, A.A. and Holtkamp-Tacken, E. (2004) Hypersaline microbial systems of sabkhas: examples of life's survival in "extreme" conditions. Astrobiology 4, 450-459.

Lange, O.L., Kilian, E. and Ziegler, H. (1986) Water vapor uptake and photosynthesis of lichens: performance differences in species with green and blue-green algae as phycobionts. Oecologia 71, 104-110.

Langevin, Y., Poulet, F., Bibring, J.-P. and Gondet, B. (2005) Sulfates in the North Polar region of Mars detected by OMEGA/Mars Express. Science 307, 1584-1586.

Madigan, M.T., Martinko, J.M. and Parker, J. (2003) Brock Biology of Microorganisms. Prentice-Hall, Upper Saddle River, NJ (tenth edition).

Maier, R.M., Drees, K.P., Neilson, J.W., Henderson, D.A., Quade, J. and Betancourt, J.L. (2004) Microbial life in Atacama Desert. Science 306, 1289-1290.

McKay, C.P., Friedmann, E.I., Warthon, R.A. and Davies, W.L. (1992) History of water on Mars: a biological perspective. Adv. Space Res. 12, 231-238.

McKay, C.P., Friedmann, E.I., Gomez-Silva, B., Caceres Villanueva, L., Andersen Dale, T. and Landheim, R. (2003) Temperature and moisture conditions for life in the extreme arid region of the Atacama Desert: four years of observations including the El Nino of 1997-1998. Astrobiology 3, 393-406.

McLennan, S.M., Bell, J.F. III, Calvin, W.M., et al. (2005) Provenance and diagenesis of the evaporite-bearing Burns formation, Meridiani planum, Mars. Earth Planet. Sci. Lett 240, 95-121.

Navarro-Gonzales, R., Rainey, F.A., Molina, P., Bagaley, D.R., Hollen, B.J., de la Rosa, J., Small, A.M., Quinn, R.C., Grunthaner, F.J., Caceres, L., Gomez-Silva, B. and McKay, C.P. (2003) Mars-like soils in the Atacama Desert, Chile, and the dry limit of microbial life. Science 302, 1018-1021.

Nienow, J.A., McKay C.P. and Friedamnn, E.I. (1988a) The cryptoendolithic microbial environment in the Ross Desert of Antarctica: mathematical models of the thermal regime. Microb. Ecol. 16, 253-270.

Nienow, J.A., McKay, C.P. and Friedamnn, E.I. (1988b) The cryptoendolithic microbial environment in the Ross Desert of Antarctica: light in the photosynthetically active region. Microb. Ecol. 16, 271-289.

Omelon, C.R., Pollard, W.H. and Ferris, F.G. (2006a) Chemical and ultrastructural characterization of high Artic cryptoendolithic habitats. Geomicrobiol. J. 23, 189-200.

Omelon, C.R., Wayne, H.P. and Ferris, F.G. (2006b) Environmental controls on microbial colonization of high Arctic cryptoendolithic habitats. Polar Biol. 30, 19-29.

Onofri, S., Selbmann, L., Zucconi, L. and Pagano, S. (2004) Antarctic microfungi as models for exobiology. Planet. Space Sci. 52, 229-237.

Oren, A., Kuhl, M. and Karsten, U. (1995) An endevaporitic microbial mat within a gypsum crust: zonation of phototrophs, photopigments, and light penetration. Mar. Ecol. Prog. Ser. 128, 151-159.

Palmer, R.J. and Friedmann, E.I. (1990) Water relations and photosynthesis in the cryptoendolithic microbial habitat of hot and cold deserts. Micro. Ecol. 19, 111-118.

Pointing, S.B., Kimberley, A.W., Lacap, D.C., Rhodes, K.L. and McKay, C.P. (2007) Hypolithic community shifts occur as a result of liquid water availability along environmental gradients in China's hot and cold hyperarid deserts. Env. Microbiol. 9, 414-424.

Potts, M. (1994) Dessication tolerance of prokaryotes. Microbiol. Rev. 58, 755-805.

Potts, M. and Friedmann, E.I. (1981) Effects of water stress on Cryptoendolihic cyanobacteria from hot desert rocks. Arch. Microbiol. 130, 267-271.

Rodriguez-Valera, F., Ruiz-Berraquero, F. and Ramos-Cormenzana, A. (1981) Characteristics of the heterotrophic bacterial populations in hypersaline environments of different salt concentrations. Microb. Ecol. 7, 235-243.

Satterfield, C.L., Lowenstein, T.K., Vreeland, R.H., Rosenzweig, W.D. and Powers, D.W. (2005) New evidence for 250 Ma age of halotolerant bacterium from a Permian salt crystal. Geology 33, 265-268.

Sawyer, D.J., McGehee, M.D., Canepa, J. and Moore, C.B. (2000) Water soluble ions in the Nakhla Martian meteorites. Meteoritics & Planet. Sci 35, 743-747.

Siebert, J. and Hirsch, P. (1988) Characterization of 15 selected coccal bacteria isolated from Antarctica rock and soil samples from the McMurdo-Dry Valleys (South Victoria Land). Polar Biol. 9, 37-44.

Siebert, J., Hirsch, P., Hoffmann, B., Gliesche, C.G., Peissl, K. and Jendrach, M. (1996) Biodivers. Conserv. 5, 1337-1363.

Squyres, S.W., Arvidson, R.E., Bell, J.F. III, et al. (2004) The Spirit Rover's Athena Science Investigation at Gusev crater, Mars. Science 35, 794-799.

Sun, H.J. and Friedmann, E.I. (1999) Growth on geological time scales in the Antarctic cryptoendolithic microbial community. Geomicrobiol. J. 16, 193-202.

Treiman, A.H., Gleason, J.D. and Bogard, D.D. (2000) The SNC meteorites are from Mars. Planet. Space Sci. 48, 1213-1230.

Vaniman, D.T., Bish, D.L., Chipera, S.J., Fialips, C.I., Carey, J.W. and Feldman, W.C. (2004) Magnesium sulphate salts and the history of water on Mars. Nature 431, 663-665.

Vestal, J.R. (1988) Carbon metabolism in the cryptoendolithic microbiota in the Antarctic desert. Appl. Environm. Microbiol. 54, 960-965.

Villar, S.E.J., Edwards, H.G.M. and Cockell, C.S. (2005) Raman spectroscopy of endoliths from Antarctic cold desert environments. Analyst 130, 156-162.

Vreeland, R.H., Rosenzweig, W.D. and Powers, D.W. (2000) Isolation of a 250 million-year-old halotolerant bacterium from a primary salt crystal. Nature 407, 897-900.

Walker, J. and Pace, N.R. (2007) Endolithic microbial ecosystems. Annu. Rev. Microbiol. 61, 331-347.

Warren-Rhodes, K.A., Rhodes, K.L., Pointing, S.B., Ewing, S., Lacap, D.C., Gomez-Silva, B., Amundson, R., Friedmann, E.I. and McKay, C.P. (2006) Hypolithic cyanobacteria, dry limit of photosynthesis and microbial ecology in the hyperarid Atacama Desert. Microb. Ecol 52, 389-398.

Wierzchos, J. and Ascaso, C. (2001) Life, decay and fossilzation of endolithic microorganisms from the Ross Desert, Antartctica. Polar Biol. 24, 863-86

Wierzchos, J. and Ascaso, C. (2002) Microbial fossil record of rocks from the Ross Desert, Antarctica: implications in the search for past life on Mars. Int. J. Astrobiology 1, 51-59.

Wierzchos, J., Ascaso, C., Rancho, L.G. and Green, A. (2003) Iron- rich diagenetic minerals are biomarkers of microbial activity in Antarctic rocks. Geomicrobiol. J. 20, 15-24.

Wierzchos, J., De Los Rios, A., Sancho, L.G. and Ascaso, C. (2004) Viability of endolithic microorganisms in rocks from McMurdo Dry Valley of Antarctica established by confocal and fluorescence microscopy. J. Microscopy 216, 57-61.

Wierzchos, J., Sancho, L.G. and Ascaso, C. (2005) Biomineralization of endolithic microbes in rocks from the Mcmurdo Dry Valleys of Antarctica: implications for microbial fossil formation and their detection. Environm. Microbiol. 7, 566-575.

Wierzchos, J., Ascaso, C. and McKay, C.P. (2006) Endolithic Cyanobacteria in Halite Rocks from the Hyperarid Core of the Atacama Desert. Astrobiology 6, 415-422.

Wynn-Williams, D.D. and Edwards, H.G.M. (2000) Antarctic ecosystems as model for extraterrestrial surface habitats. Planet. Space Sci. 48, 1065-1075.

Wynn-Williams, D.D., Edwards, H.G.M., Newton, E.M. and Holder J.M. (2002) Pigmentation as a survival strategy for ancient and modern photosynthetic microbes under high ultraviolet stress on planetary surface. Int. J. Astrobiology 1, 39-49.

Biodata of Ioan I. Ardelean, author of "Magnetotactic Bacteria and Their Potential for Terraformation"

Dr. Ioan I. Ardelean is currently Principal Senior Researcher at the Institute of Biology of the Romanian Academy. He obtained his Ph.D. from Institute of Biology in 1998, and continued his studies and research at the Institute of Biology. Since 2005, Ioan I. Ardelean is Associated Professor at the 'Ovidius' University, Constantza. His scientific interests are in the areas of: bacteria-based biosensors, hydrogen metabolism in phototrophic bacteria, biology of magnetotactic bacteria and their relevance for bionanotechnology and terraformation.

E-mail: [email protected]

Biodata of Cristina Moisescu, co-author of "Magnetotactic Bacteria and Their Potential for Terraformation"

Cristina Moisescu is currently Researcher at the Institute of Biology of the Romanian Academy. Since 2007 she is a Ph.D. student at the 'Ovidius' University, Constantza. Her scientific interest is on the biology of magnetotactic bacteria with special emphasis on magnetosome biomineralization, micro-structural characteristics of biogenic magnetite crystals extracted from Magnetospirillum gryph-iswaldense and the potential of this novel class of magnetic nanoparticles for various biomedical and technological applications.

E-mail: [email protected]

loan I. Ardelean

Cristina Moisescu loan I. Ardelean

Cristina Moisescu

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