Resistance of the LichenBuellia frigidato Simulated Space Conditions during the Preflight Tests for BIOMEX—Viability Assay and Morphological Stability

Abstract

Samples of the extremotolerant Antarctic endemite lichen Buellia frigida are currently exposed to low-Earth orbit-space and simulated Mars conditions at the Biology and Mars Experiment (BIOMEX), which is part of the ESA mission EXPOSE-R2 on the International Space Station and was launched on 23 July 2014. In preparation for the mission, several preflight tests (Experimental and Scientific Verification Tests, EVT and SVT) assessed the sample preparation and hardware integration procedures as well as the resistance of the candidate organism toward the abiotic stressors experienced under space and Mars conditions. Therefore, we quantified the post-exposure viability with a live/dead staining technique utilizing FUN-1 and confocal laser scanning microscopy (CLSM). In addition, we used scanning electron microscopy (SEM) to investigate putative patterns of morphological-anatomical damage that lichens may suffer under the extreme exposure conditions. The present results demonstrate that Buellia frigida is capable of surviving the conditions tested in EVT and SVT. The mycobiont showed lower average impairment of its viability than the photobiont (viability rates of >83% and >69%, respectively), and the lichen thallus suffered no significant damage in terms of thalline integrity and symbiotic contact. These results will become essential to substantiate and validate the results prospectively obtained from the returning space mission. Moreover, they will help assess the limits and limitations of terrestrial organisms under space and Mars conditions as well as characterize the adaptive traits that confer lichen extremotolerance.

Survival, DNA, and Ultrastructural Integrity of a Cryptoendolithic Antarctic Fungus in Mars and Lunar Rock Analogs Exposed Outside the International Space Station

“…To accomplish such investigations, the responses of microorganisms, such as bacterial cells and spores, cyanobacteria, fungi and lichens, to selected space factors (microgravity, galactic cosmic radiation, solar UV radiation, and space vacuum) have been the subject of study over the course of the past two decades in both laboratory simulations and space experiments (Billi et al, 2000;de Vera et al, 2002de Vera et al, , 2004Demets et al, 2005;de la Torre Noetzel et al, 2007;de la Torre et al, 2010;Sancho et al, 2007Sancho et al, , 2008Onofri et al, 2008Onofri et al, , 2012Onofri et al, , 2015Olsson-Francis et al, 2009;Horneck and Baumstark-Khan, 2012;Baqué et al, 2013;Meeßen et al, 2015).…”

Characterization of Viability of the Lichen Buellia frigida After 1.5 Years in Space on the International Space Station

“…Experiments verified that lichens may survive desiccation for up to 13 years at -20°C (Honegger, 2003). B. frigida can be described by a wide variety of adaptation strategies considering the severe environmental conditions at the respective Antarctic habitats (Nybakken et al, 2004;de Vera et al, 2008;Backhaus et al, 2014;Meeßen et al, 2015). Regarding the stress factor desiccation, lichens are able to activate repair mechanisms, for example, DNA repair processes (Eker et al, 1994;Petersen et al, 1999;Sinha and Häder, 2002;Buffoni Hall et al, 2003).…”

“…The present study focuses on the viability of the lichen B. frigida and its symbionts after 469 days of space exposure as part of the BIOMEX project. Preflight tests analyzed the lichen's resistance to abiotic stressors such as vacuum, Mars atmosphere, temperature cycling, and monochromatic UVC 254nm fluences for up to 38 days (Meeßen et al, 2015). While B. frigida demonstrated a high resistance to these simulated stressors, the exposure to real space stressors in combination for 1.5 years strongly impaired the survival potential of this lichen.…”

“…In advance of the BIOMEX project, the effects of extraterrestrial stressors on B. frigida had been analyzed in preflight simulation tests. The tests assessed the resistance of the lichen B. frigida to abiotic stressors (e.g., vacuum, Mars atmosphere, UVC radiation, temperature cycling, and temperature extremes) (Meeßen et al 2015) that occur at simulated space and martian surface conditions. The postflight mortality was determined by LIVE/DEAD staining with FUN Ò 1 and confocal laser scanning microscopy.…”

Mosses in Low Earth Orbit: Implications for the Limits of Life and the Habitability of Mars

“…A range of organisms have already been investigated in these habitats such as microbial communities collected in permafrost soils (Hansen et al, 2009), endolithic cyanobacteria from deserts (Baqué et al, 2013), or cryptoendolithic fungi from Antarctica Selbmann et al, 2015;Pacelli et al, 2016). Furthermore, epilithic organisms were frequently investigated, such as phototrophic biofilms Cockell et al, 2011) or a wide range of lichens from northern hemispheric steppes (de la Torre et al, 2010;Sánchez et al, 2012), continental Antarctica (de Vera et al, 2014;Meeßen et al, 2015), as well as from polar and alpine habitats (de Vera, 2012;Brandt et al, 2016Brandt et al, , 2017.…”