Abstract EANA2025-95

Understanding where and how life exists and evolves is one of the main objectives of astrobiological missions, with the aim of laying the groundwork for future space exploration.
Cyanobacteria were the first organisms to develop oxygenic photosynthesis using solar radiation and to cope with UV radiation damage before the oxygenation of Earth’s atmosphere. Recently, their remarkable ability to remodel the composition of the photosynthetic apparatus to absorb far-red light, thanks to novel chlorophylls such as Chl-d and Chl-f, has been discovered. This phenomenon, known as Far-Red Light Photoacclimation (FaRLiP) represents an ancestral form of oxygenic photosynthesis. This finding may reveal how these cyanobacteria endure extreme environments analogous to Mars and provide insights into the habitability potential of exoplanets orbiting M-type stars, whose emission spectra are enriched in far-red light.

In this context, the ASTERIA project aims to investigate the UV radiation adaptability of cyanobacteria of the genus Chroococcidiopsis spp., already known for their resistance to UV radiation ionizing radiation and desiccation, as well as their capacity for far-red light photosynthesis. These studies will help define the surface habitability of the Archean Earth, Noachian Mars, and exoplanets around M-type stars.

To this end, the adaptability of Chroococcidiopsis sp. 010 was assessed through controlled laboratory simulations replicating Mars-like environmental conditions at the Planetary Analogue Simulation Laboratory (PASLAB) of the DLR Institute of Planetary Research in Berlin. The aim was to investigate the feasibility of photosynthesis in near-surface protected niches. Survival and growth were monitored in real time using a Mini PAM photosynthesis yield analyzer to evaluate photosynthetic activity. At the end of the exposure, advanced cell-proliferation assays, including Calcein-AM staining and AlamarBlue tests, were conducted to provide sensitive measurements of cell viability and metabolic activity.

In addition, Chroococcidiopsis sp. CCMEE 010 and CCMEE 130 were analyzed for the stability of biosignatures after six years of desiccation. Confocal laser scanning microscopy and Raman spectroscopy demonstrated the detectability of these biosignatures, highlighting that these two FaRLiP cyanobacteria constitute a novel reservoir of diverse pigments, including canonical chlorophyll a, far-red-shifted chlorophylls, phycobiliproteins, and carotenoids.

To further elucidate the mechanisms underlying stress response and adaptation, a combination of comparative genomic and transcriptomic analyses will be performed to enable a detailed investigation of gene expression patterns and evolutionary adaptations. Additionally, by studying the strategies employed by microorganisms to withstand extreme conditions, we may uncover unexpected resistance mechanisms. This integrative approach will help define the physical and chemical boundary conditions of Earth’s environments and compare them with those on other planetary bodies to assess whether life could originate, evolve, or persist elsewhere in our Solar System.

The results of this project will advance our understanding of the only form of life known to us, offering valuable insights into the past habitability of Mars and the potential for oxygenic photosynthesis on planets orbiting stars other than the Sun.