Desert cyanobacteria, lichens, and bryophytes (mosses) possess three adaptations critical to their existence near the dry limit of habitability. These include 1) poikilohydry, the ability to survive…

This is a $516,874.00 grant awarded by a civilian federal agency to the Desert Research Institute (DRI), which is a non-profit research organization within the Nevada System of Higher Education. The grant is for research on the adaptations of desert cyanobacteria, lichens, and mosses that allow them to survive extreme environmental conditions near the limits of habitability, with a focus on their tolerance to wet-dry cycles, UV radiation, and oxidation. The research aims to challenge the notion that a UV-attenuating atmosphere is necessary for the habitability of Mars. This grant does not have a set-aside designation, indicating it was awarded on an unrestricted, competitive basis. DRI, as a subsidiary of the State of Nevada, has a proven track record of securing federal contracts and grants for specialized scientific research and technical services across various domains, including climate science, environmental monitoring, and technology development.

Desert cyanobacteria, lichens, and bryophytes (mosses) possess three adaptations critical to their existence near the dry limit of habitability. These include 1) poikilohydry, the ability to survive dehydration in a vegetative state 2) sun screens, the ability to fortify their thallus or cell surface with pigments that are optically opaque to ultraviolet rays (UV) but relatively transparent to photosynthetically active radiation and 3) antioxidants, which are necessary during long periods of dehydration and metabolic inactivity. In a preliminary study initiated to determine whether or not these adaptations have a limit, we challenged dried cyanobacteria and lichens to wet-dry cycles, UVC (254 NM, 4.7 watts/M2), and 5% O3. Afterward, we rehydrated the organisms and monitored their photosynthetic recovery using a pulse-amplitude-modulated chlorophyll fluorometer (PAM). Results thus far indicate that the organisms are effectively insensitive to wet-dry cycles and UVC, but they are susceptible to extreme oxidation. In oxidation resistance, lichens outperformed cyanobacteria presumably because they have a more sophisticated thallus with a multi-layered antioxidant defense. This proposal seeks to evaluate these insights with three species from each group by determining their tolerance under more controlled conditions, including 1) a rapid sequence of wet-dry cycles in an anaerobic glovebox in the dark without opportunity for repair, 2) high-intensity UVC irradiation (9 watts/M2) in ambient air, 3) high-intensity UVC irradiation in CO2 to keep out O3, and 4) 5% O3. Photobiont viability will be assessed using PAM chlorophyll fluorometry and 14CO2 labeled uptake. In O3-killed specimens, oxidation biomarkers specific to polysaccharides, lipids, and proteins separating cytosolic and DNA/nucleusassociated proteins will be quantified to understand death by oxidation at the molecular level. Results are expected to challenge the notion that a UVC-attenuating atmosphere is a necessary condition for surface biota to show that dry limits are because of oxidation rather than desiccation and to reveal the possibility that anaerobic worlds are without dry limits.