Abstract EANA2026-76

In the context of space exploration it is fundamental to understand the effect of the lunar environment on terrestrial organisms as the Moon is a solid target and will also constitute the testbed for Mars exploration. Exposure experiments demonstrated the capabilities of certain organisms to withstand high radiation levels (1), with promising results coming from dessicated fungi (2) and cyanobacterial biofilms (3).  Nonetheless, most of these studies have been performed on Earth or in Low Earth Orbit, where radiations are partially shielded by the geomagnetic field, and metabolic recovery after exposure has been commonly evaluated under terrestrial conditions.

In this frame, the EXTREMOON project addresses the biological sensitivity of active microorganisms in the lunar environment, testing their tolerance and capacity of maintaining metabolic activity. The project was selected as part of the ESA AO 2022 “Reserve Pool of Science Activities for the Moon: A SciSpacE Announcement of Opportunity.” and foresees the exposure of microbial cells to the lunar surface environment inside dedicated payloads.

The biomass in the payload will be in desiccated state during flight, and will be rehydrated once on the moon surface. In order to design a functional payload, it is crucial to set how to probe metabolic recovery after rehydration and the time required for full recovery. One of the selected organisms is the polyextremophyle cyanobacterium Chlorogleopsis fritschii. We considered this strain as it resists strong UV radiation via the synthesis of UV protective molecules, mycosporine-glicine and schinorine, whose synthesis is also induced upon exposure to far-red light. Far-red light, which in most phototrophs does not drive oxygenic photosynthesis, can be exploited by this cyanobacterium via the Far-Red Light Photoacclimation (FaRLiP), which allows growth relying on such low-energetic photons [4]. This reversible response involves a profound remodeling of photosynthetic complexes, which incorporate newly synthesized long-wavelength absorbing pigments, as chlorophyll f and d.

The proposed contribution will illustrate the potential of the reversion of the far-red light acclimation as a tool to monitor survival and metabolic rescue during recovery after cultures rehydration in visible light. 

To this aim we carried out preliminary ground based experiments, evaluating the desiccation tolerance of C. fritschiiacclimated either to visible or far-red light. Recovery of growth and metabolic processes after rehydration were evaluated with a focus on the impact of the FaRLiP acclimation on i) cell resilience, ii) pigment stability and iii) methodologic ease in detecting the metabolic rescue. 

The obtained data enabled the definition of key parameters for payload design in terms of timing required for recovery and detection methods. Beyond this, the experiments underline the potential contribution of far-red light user cyanobacteria to life support systems and provide insights in the preservation and stability of chlorophyll f as a potential biosignature.

 

[1] de Vera et al., 2019 https://doi.org/10.1089/ast.2018.1897

[2] Onofri et al., 2015 https://doi.org/10.1089/ast.2015.1324

[3] Billi et al., 2019 https://doi.org/10.1089/ast.2018.1900

[4] Gan & Bryant, 2015 https://doi.org/10.1111/1462-2920.12992