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

Unearthing terrestrial extreme microbiomes for searching terrestrial-like life in the Solar System

The possibility of life elsewhere in the universe has fascinated humankind for ages. To the best of our knowledge, life, as we know it, is limited to planet Earth; yet current investigation suggests that life might be more common than previously thought. In this review, we explore extreme terrestrial analogue environments in the search for some notable examples of extreme organisms, including overlooked microbial groups such as viruses, fungi, and protists, associated with limits of life on Earth. This knowledge is integral to provide the foundational principles needed to predict what sort of Earth-like organisms we might find in the Solar System and beyond, and to understand the future and origins of life on Earth.

Beyond the extremes: Rocks as ultimate refuge for fungi in drylands

In an era of rapid climate change and expansion of desertification, the extremely harsh conditions of drylands are a true challenge for microbial life. Under drought conditions, where most life forms cannot survive, rocks represent the main refuge for life. Indeed, the endolithic habitat provides thermal buffering, physical stability, and protection against incident ultraviolet (UV) radiation and solar radiation and, to some extent, ensures water retention to microorganisms. The study of these highly specialized extreme-tolerant and extremophiles may provide tools for understanding microbial interactions and processes that allow them to keep their metabolic machinery active under conditions of dryness and oligotrophy that are typically incompatible with active life, up to the dry limits for life. Despite lithobiontic communities being studied all over the world, a comprehensive understanding of their ecology, evolution, and adaptation is still nascent. Herein, we survey the fungal component of these microbial ecosystems. We first provide an overview of the main defined groups (i.e., lichen-forming fungi, black fungi, and yeasts) of the most known and studied Antarctic endolithic communities that are almost the only life forms ensuring ecosystem functionality in the ice-free areas of the continent. For each group, we discuss their main traits and their diversity. Then, we focus on the fungal taxonomy and ecology of other worldwide endolithic communities. Finally, we highlight the utmost importance of a global rock survey in order to have a comprehensive view of the diversity, distribution, and functionality of these fungi in drylands, to obtain tools in desert area management, and as early alarm systems to climate change.

Antioxidant and Photoprotective Metabolites of Bunodophoron melanocarpum, A Lichen from the Andean Páramo

Background: Oxidative stress caused by exposure to ultraviolet radiation has been associated with dermal problems, including skin cancer. In this study, we determined the photoprotective and antioxidant activity of isolated metabolites from the lichen Bunodophoron melanocarpum (Sphaerophoraceae) to find new sunscreens prototypes. Methods: The constituents of B. melanocarpum were isolated by phytochemical methods and their structures were determined by spectroscopy (IR, 1D and 2D NMR). Antioxidant activity was measured by scavenging DPPH free radicals (EC50), ferric reducing power (FRP), and inhibition of lipid peroxidation (% ILP). The photoprotective capacity against ultraviolet(UVA and UVB) radiations was determined in vitro by calculating their sun protection factor(SPF), critical wavelength and UVA ratio and these values were compared against commercial sunscreens. The lipophilicity and possible skin penetration to the lipid-rich stratum corneum of the isolates, was determined by calculating their octanol/water partition coefficients (Log P) and Gibbs free energy of transfer (ΔtG0 ). Results: Sphaerophorin (1), everninic acid (2), sphaerophorol carboxylic acid (3) and friedelin(4) were isolated from B. melanocarpum. Orsellinic acid-type compounds 1 and 3 are dual agents with antioxidant capacity as free radical scavengers (EC50= 0.0857 and 0.1828 mol compound /mol DPPH•, respectively) and photoprotective properties particularly against UVB radiation(SPF 25.78 ± 0.53 and 22.00 ± 1.03, respectively). In addition, they had lipophilicity (Log P 7.07 ±0.64 and 4.03 ± 0.32, respectively) and ΔtG0 (-40.32 ± 3.67 and -22.97 ± 1.82 kJmol-1, respectively)suitable to act on the skin. Conclusion: Sphaerophorin (1) and sphaerophorol carboxylic acid (3) are dual agents with antioxidant and UVB photoprotective properties and are also lipophilic substances that spontaneously would diffuse across the skin.

Limits of Life and the Habitability of Mars: The ESA Space Experiment BIOMEX on the ISS

BIOMEX (BIOlogy and Mars EXperiment) is an ESA/Roscosmos space exposure experiment housed within the exposure facility EXPOSE-R2 outside the Zvezda module on the International Space Station (ISS). The design of the multiuser facility supports-among others-the BIOMEX investigations into the stability and level of degradation of space-exposed biosignatures such as pigments, secondary metabolites, and cell surfaces in contact with a terrestrial and Mars analog mineral environment. In parallel, analysis on the viability of the investigated organisms has provided relevant data for evaluation of the habitability of Mars, for the limits of life, and for the likelihood of an interplanetary transfer of life (theory of lithopanspermia). In this project, lichens, archaea, bacteria, cyanobacteria, snow/permafrost algae, meristematic black fungi, and bryophytes from alpine and polar habitats were embedded, grown, and cultured on a mixture of martian and lunar regolith analogs or other terrestrial minerals. The organisms and regolith analogs and terrestrial mineral mixtures were then exposed to space and to simulated Mars-like conditions by way of the EXPOSE-R2 facility. In this special issue, we present the first set of data obtained in reference to our investigation into the habitability of Mars and limits of life. This project was initiated and implemented by the BIOMEX group, an international and interdisciplinary consortium of 30 institutes in 12 countries on 3 continents. Preflight tests for sample selection, results from ground-based simulation experiments, and the space experiments themselves are presented and include a complete overview of the scientific processes required for this space experiment and postflight analysis. The presented BIOMEX concept could be scaled up to future exposure experiments on the Moon and will serve as a pretest in low Earth orbit.