Search

The role of DNA repair by nonhomologous end joining (NHEJ), homologous recombination, spore photoproduct lyase, and DNA polymerase I and genome protection via [alpha]/[beta]-type small, acid-soluble spore proteins (SASP) in Bacillus subtilis spore resistance to accelerated heavy ions (high-energy charged [HZE] particles) and X rays has been studied. Spores deficient in NHEJ and [alpha]/[beta]-type SASP were significantly more sensitive to HZE particle bombardment and X-ray irradiation than were the recA, polA, and splB mutant and wild-type spores, indicating that NHEJ provides an eflicient DNA double-strand break repair pathway during spore germination and that the loss of the [alpha]/[beta]-type SASP leads to a significant radiosensitivity to ionizing radiation, suggesting the essential function of these spore proteins as protectants of spore DNA against ionizing radiation.

Bacterial spores (Bacillus subtilis), cyanobacteria (Chroococcidiopsis sp.), and lichen (Xanthoria elegans) embedded in martian analogue rock (gabbro) were exposed to shock pressures between 5 and 50 GPa which is the range of pressures observed in martian meteorites. The survival of Bacillus subtilis and Xanthoria elegans up to 45 GPa and of Chroococcidiopsis sp. up to 10 GPa supports the possibility of transfer of life inside meteoroids between Mars and Earth and it implies the potential for the transfer of life from any Mars-like planet to other habitable planets in the same stellar system. Keywords: Mars; Impact processes; Astrobiology; Meteorites; Experimental techniques

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.spacepol.2006.08.006 Byline: Charles S Cockell (a), Gerda Horneck (b) Abstract: Building on an earlier article, establishment of a planetary park system for other planetary bodies is further developed. Reasons are elaborated for such a system to protect representative regions of other planetary bodies. Although a parks system might seem supererogatory, and an over-reaction to the currently very limited environmental impact of robotic and human exploration and settlement activities, four arguments are provided that suggest that such a system does have a value, even in advance of robotic and human missions. Planetary parks incorporate concepts of planetary protection, but they extend the reasons for practical protection policies beyond the utilitarian protection of scientific resources emphasized by planetary protection, into other utilitarian and intrinsic value arguments. Planetary parks might still allow for the development of non-park areas by commercial enterprise. Author Affiliation: (a) Open University, Milton Keynes, MK7 6AA, UK (b) German Aerospace Center DLR, Institute of Aerospace Medicine, D 51170 Cologne, Germany

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.spacepol.2004.08.003 Byline: Charles Cockell (a), Gerda Horneck (b) Abstract: The increasing robotic exploration of Mars and eventual human exploration and settlement of that planet threatens to have a significant environmental impact on scientifically important sites and sites of natural beauty in the form of contamination with micro-organisms and spacecraft parts. By definition, the sites that we might wish to preserve are likely to be those to which robots and humans will be sent. An interventionist step to protect pristine regions of Mars with the formation of a Planetary Park system is proposed. Possible locations for the first seven Planetary Parks are suggested. Landing of unmanned craft in these parks would be forbidden. Although global dust storms can carry microorganisms across the planetary surface, the regulations suggested for these parks will allow for the maximum level of preservation. We also suggest that the Planetary Park system could be applied to the Moon. Author Affiliation: (a) British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK (b) German Aerospace Center, Institute of Aerospace Medicine, 51170 Cologne, Germany

Models of spore resistance mechanisms are discussed, focusing on the endospores of Bacillus spp. Spores are one of the hardiest forms of life on Earth and can survive both terrestrial and extra-terrestrial environmental extremes.

The influence of the seasonal stratospheric ozone depletion on the ultraviolet (UV) climate in Antarctica was studied using Bacillus subtilis spores as a biological test system. The test strain was deficient in DNA repair. The UV-induced loss of colony-forming activity was measured and inactivation constants calculated. The trend of UV-B radiation was found to be season-dependent, and the UV-B levels were biologically harmful and were higher than expected values. The thickness of the ozone column was, therefore, shown to have an influence on the biologically harmful UV-B on the ground.