Abstract EANA2026-21

Radiation represents one of the major environmental constraints for the survival of life beyond Earth and is therefore a central topic in astrobiology. Understanding the mechanisms underlying microbial resistance to ionizing and ultraviolet radiation is crucial for the possibility of life on potential habitable worlds, as well as the development of biological systems supporting future human space exploration. In this context, cyanobacteria have emerged as highly relevant model organisms due to their metabolic versatility and remarkable tolerance to extreme environmental conditions. Among radioresistant microorganisms, cyanobacteria belonging to the genus Chroococcidiopsis are considered prime candidates for astrobiology studies because of their exceptional resistance to solar and cosmic radiation, desiccation, and other environmental stresses. Desert strains of this genus dominate lithic communities in terrestrial Mars analogue environments characterized by aridity, intense UV exposure, and extreme temperature fluctuations. Moreover, several Chroococcidiopsis strains have demonstrated high survival rates under simulated Martian and space conditions, including experiments performed aboard the International Space Station and ground-based irradiation campaigns. These characteristics make them valuable models not only for investigating the limits of life, but also for the development of chasses for biotechnological applications aimed at supporting long-term human exploration of the Moon and Mars. The molecular basis of this extraordinary radioresistance remains only partially understood and requires investigation through integrated omics approaches. In this study, comparative genomic analyses were performed to enable a detailed investigation of genes involved in radiation resistance mechanisms in Chroococcidiopsis sp. 029. In particular, attention was devoted to genes associated with DNA repair, oxidative stress response, cellular protection pathways, and the synthesis of nucleoid-associated proteins (NAPs), which are widely distributed in prokaryotes and play protective roles under stress conditions. Among NAPs, Dps (DNA-binding proteins from starved cells) are known to play a pivotal role in protecting DNA from oxidative damage by physically shielding the nucleoid and scavenging reactive oxygen species through their ferroxidase activity, thereby limiting the Fenton reaction. Structural and dynamic characterization of putative Dps proteins is currently underway through computational and structural bioinformatics approaches to investigate their conformational properties and potential DNA-binding activity in radiation-tolerant Chroococcidiopsis strains. Furthermore, transcriptomic analyses were conducted following exposure of hydrated Chroococcidiopsis sp. 029 cells to 5 kGy gamma radiation and the differential gene expression was analysed after 3, 6, and 12 hours of recovery. Overall, this work aims to provide new insights into the molecular determinants of radiation resistance in desert cyanobacteria, contributing to our understanding of microbial survival under extraterrestrial conditions and supporting future astrobiological and space biotechnology applications.