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Abstract

Spores of Bacillus subtilis, conidia of Aspergillus niger, versicolor and ochraceus and cells of Deinococcus radiodurans have been exposed in the dark at two locations (at about 23 degrees S and 24 degrees S) in the Atacama Desert for up to 15 months. B. subtilis spores (survival approximately 15%) and A. niger conidia (survival approximately 30%) outlived the other species. The survival of the conidia and spores species was only slightly poorer than that of the corresponding laboratory controls. However, the Deinococcus radiodurans cells did not survive the desert exposure, because they are readily inactivated at relative humidities between 40 and 80% which typically occur during desert nights. Cellular monolayers of the dry spores and conidia have in addition been exposed to the full sun light for up to several hours. The solar fluences causing 63% loss in viability (F37-values) have been determined. These F37-values are compared with those determined at other global locations such as Punta Arenas (53 degrees S), Key Largo (25 degrees N) or Mainz (50 degrees N) during the same season. The solar UVB radiation kills even the most resistant microorganisms within a few hours due to DNA damages. The data are also discussed with respect to possible similarities between the climatic conditions of the recent Atacama Desert and the deserts of early Mars.

Living at the Extremes: Extremophiles and the Limits of Life in a Planetary Context

“…The parameters discussed herein (temperature, pH, pressure, and salinity, and radiation) correlate with each other and can influence the availability of nutrients and energy sources. Depending on the environment, certain parameters can more strongly influence microbial diversity over others, such as temperature in geothermal waters (Sharp et al, 2014), pH in soil communities (Rousk et al, 2010), salinity in saline lakes (Yang et al, 2016), and water content in dry climates (Dose et al, 2001). On the nanoand micro-scale level, the two most important factors are likely water activity and pH, which influence the chemiosmotic, energy-generating gradient at the cell level (Lane et al, 2010;Lane and Martin, 2012).…”

Fungal and Bacterial Microbiome Associated with the Rhizosphere of Native Plants from the Atacama Desert

“…The Atacama Desert is located in northern Chile and is described as the driest and oldest in the world [13]. In addition to aridity, the Atacama Desert has other environmental factors such as strong thermal oscillation, low relative humidity levels, low water retention [14], high levels of ultraviolet radiation [15], extreme oligotrophic conditions, high salinity, and high levels of inorganic oxidants in soil [16].…”

Living at the Frontiers of Life: Extremophiles in Chile and Their Potential for Bioremediation

“…Arid areas are biomes with a ratio of mean annual rainfall to mean annual evaporation of <0.05 mm year -1 , and <0.002 mm year -1 for extreme hyper-arid areas ( Mohammadipanah and Wink, 2016 ). In addition to the low rainfall, other factors such as high and low temperatures, low water activity, high salinity, low concentrations of organic carbon and intense radiation intensify the xeric conditions, constraining the survival of microorganisms ( Dose et al, 2001 ; Crits-Christoph et al, 2013 ).…”

“…Evasion of dry environmental implies the conversion of cells into a state of non-replicative viability through the formation of spores ( Crits-Christoph et al, 2013 ). Adaptative mechanisms are associated to preventing water loss and increasing water retention through the accumulation of osmoprotectants (trehalose, L -glutamate, glycine betaine), production of extracellular polymeric substances (EPS), modifications on the cell membrane to retain intracellular water, and synthesis of DNA-repair proteins ( Dose et al, 2001 ; Lebre et al, 2017 ).…”